ren(e of ci:sease.

" Microorganisms alsc interactby the use of chemical signal

I

icroorganismInte!'actions andMicrobial Ecology

Concepts. Most microorganisms in complex communities have not

been grorvn or characterized. This has limited our under-standing of microorganism interactions and their roles innature and disease. Molecular techniques are providing a

better uncierstanding of these uncultured organisms.. The term syrnbiosis, or "together-life," can be used to de-

scribe many of the interactions between microorganisms,and also microbial interactions with higher organisms. in-gtuding plants and animals. These interactions may be pos-itive or negative.

. Microbiai ecology is the study of microbial relationshipswith other organisms and also with their nonliving envi-ronr..er+s. ihese relationships, based on interactive uses ofresources, have effects extending to the global scale.

. Symbiotic interactions includd' mutualism, cooperation,commensalism. parasitism, predation, amensalism, andcompetition- These interactions are important in naturalprocesses and in the occurrence of dis-ease. The interactions can vary de-pending or the envi;'cnment andchanges in ihe interaciing or-ganisms.l,'i;:'ccrga',s.ias, a! :1e, ir:eral:,<an iorm con-rp!ex o::i,sir;i assern-blages that incluoe particularlybicfilms. Ti-:ese forn cn iiving andineri surfaces and ha;e ,'najor impactson microbial survivai and the occur-

molecules, r.,;hich - lov.' the microbial popula-tion to respond to increased population density.5uch responses incluce quorum sensing, which con-trois a wicie variety of nricroorganism properties.

llicrrr.-rganisnir iir in! in c;., ironnrcnt\ $ here

ntost knotln trr-girnisttts cann()t \un i\ e are

imporlant tor understandin,r m:e robialdiversitr. Thcrc :lrands of iron-oridizinSFct'ntplu:nttt $ ere discole red :rroi ng at

pH f) in an abandoncd rnine near Ret-lding.

Calitirrnia. This hardv micrrxrrcanisni ..:r: onlva plasma nre rrbrane to pr()te.t itsell'tionr therigors oi this h:,irsh envinrnme nt.

{

a'@i

Jt''fL

I.\

+

ffi

Energy, electrons, and nutrients must be available in a suit-

aUte "pfrvsicat

environment {or microorganisms to function'

Microbes interact'.'.'ith their environment to obtain energy

(from light or chemical sources), electrons' and nutrients'

r..vhich iJads to a p,'ocess called biogeochemical cyciing Mi-

croorganisms chanqe the physical state and mobility of

many-nutrients as ihey use them in their growth processes'

, Microorganisms a'e an important part of ecosystems' or

sel{-regrJlating biological communities and their physical

environments. Mictoorganisms play an important role insuccession,orthecredictablechangesthatoccurinecosys.tems when theY are disturbed'

, Extreme environments restrict the range of microbial types

abletosurviveancfunction.Thiscanbeduetophysicalfac-tors such as temperature, pH, pressure, or salinity' Many mi-

croorganisms iound in "extreme" environments are

"rp".Ltty adapteo not only to survive, but to function

metabolically under- these particular conditions'. Methods used to sluciy microbial interactions and microbial

ecology provide lnfcrmation on environmental characteris-

tics; riicrobial biomass, numbers, types, activity' and com-

munity structure- Microscopic, chemical, enzymatic' and

molecular techniques are used in these studies'. lt is now possible to determine the nucleic acid sequences

of specif ic microcrganisms or organelles isolated from nat-

ural environmer:s and tc study the phylogeny of uncul-

tured microorEanlsms. Tnis shoulci lead to important new

advances in :re s',,-:dy ot rr'icrobial ecology'

Et eniItitt? ls r'i t n i; -/irtr , tite cnvirottttre'$ selects'

-il.\V Beijerinck

Chapter2ShlicroorganismlnteractionsandMicrobialEcology28.2

the area of n.ricrobial ecologv (Nlicrobial Diversitl & E'cologl'

28.1i. The ternr sl,rnbiosis is usecl in its original brr.iJcst sen:e. frits an association of t\\'o ()r ntore clillerent species r)i trrganisl-lls. ,\rlJ\as susgestecl br H. A. cleBary in 1879. ;; V"

\licroorcanisnls function as populations t)l 11\\i i.llirlrtgt':'rt

sirnilar organisnts. ancl as communities. or ttlixture> trf c1itl'erent

rnicr,--rbial populations. These tllicrotlrganistrts hrLr e e voir ed

while interacting rvith the inorganic *'orld and rvirh higher trr-

ganisrns. and thel' Iar-ue11' play beneficial and Yital rtrle:: disease-

causi,tg organisnis are rtnly a minor colllponent ol the rlicrobial

world. if,licroorganisnts. as thcy inte ract u ith tlther trr{;.lt.tisttts arid

their enr.ironnlellt. also contribute to the ful-rctit'rnin: of ecos)'s-

tems. or self-regulating biological cotllutunitics an'i their phl:i-cai enr.ironnrent (pp. 603_.+). Knou'leclge ot- litcse i1i3;1161ipn: is

important in understanding both microbial cotttribr,iiiolls tt-r tire

natural u'orld and nricrobial roles in disease processi:'

.\ major prtiblet-tl in understandin-rr nricrobial interr'-iit]ns is lhi]t

most microscctpicalll, obserVablc nticrclorganisnls cannrrt be -9ro$'n.The ,lifl'erences between observable and culturable nicroorsen-

isms. $,hich limit this field even today. har,e been notei tbr at least

70 years. This problem $.as discussed in I 1931 textbcxrk ort soil nli-

crobiology u.ritten bl.Selman waksrnan, the discor er:r of strepto-

mYcin. anci advances continue in this in-rponant :Ircl '-\rg -rc'( ''i()ri

6.-5). \''lolecular rechniclues and sequence data provitle valuable in-

tbmrution on rhc-re uncultured nlicr!)olganislrlr Pr.,be: .dn be u>r-d

to bt-rrh identit-r specitrc t'rlrirnisn>r;$ilqk{ r-ttrr]er'tlnd phi:i-'rii

relationships het* een nticrohes. (ttentpt!y'r,r :lrtr* liiesc uticul-

tured micr.tes re'rains r cL-rltrirl .ffiln rnicroL'.iui ecol.Sr

t4 P'c0a-b'vw 1nt

)

{/

n prci n,it. chaptcri nitcrt>ors.rnirtns usuallr h:* e io-en

.,,,r.,,,.rcJ 3. i:oiriiirl crltirier. Thc basic ch-'irailcri\tics

Jl.i.rn.,rg"tii.;tl-. inciuiiiilg lh: structurt' enii l'unctiitn of micro-

bial cell>. rltcl:ti.,rli:i-,. Sr,-,rilh anil the a()ntr()l ol grorrth' have

been discti::cd. ln iridrtion. nlL'labolisnl' gcnetics' and molecular

aspects ol micrilorganisms. inciuding genoniics' har.e been de-

scribeci.Intiiirch;.ipier.riliertlbiliiintcr'ictiotl.rrithbilththephl,s.ical environtlle nl itnd g ilil t'r.her t'rrgatristtl: rr ili be contidcred'

Fzar FoUNDATIoNS oF MlcRoBlAL EcoLoGY\,Tuo major therllc> riill be developed in this chapter: (1) the na-

ture of microbial relationship: u ith other living organisrns' or the

nature of sl.mbioses. and tl r tl-ic intc'ractitlns ot- tile.e organisms

rriih each other and $ ith their nonliYing phy'sical environment' or

I=ZeZ MICROBIAL INTERACTIONS\,'ryIr{icroorganislns can b,-- phl'sicallr ass0ciatt:ti ri:ih oiher '-rr-ganisrns in a varietr oi r"ltr.s. One org]ni:rll cirtl n-- lrr''11!-d t'n

ttre :urfacc rrl-lnotltcr. ls rin ectosl nrhiont' i1i illi' ;l.:'c'' !h' 'J-tosl'mbiont usuailr is a snlalier organism located on the surtace

of a larger orsanisnt. ofren. clissinrilar tlrranisn'.\ (rl'sirnilar

size are in phlsical c()lllllcl. The rerrl consortium can br- u>cd

to describc' this phrsical relationship. Consortia ir aqurttic cn-

vironments are frequentll complex. involrin-u nluit'iplc lircrsof similar-looking rnicroorganisms that oiten haie conlple-

mentar)'ph1 siological properties. In contrast' Lrr' (r-!lLnL\nl

can be located rrithin another organisnl as an endosl'mbiont'

There also are rllanv cases in uhich microorgenitms lire on

both the inside and rhe outside of another or-eanism- a phert\rrll-

enon calleti ecto/endos)'mbiosis. Irlteresting erarnple: of

ecto/endosvlrlbioscs i ncl Lrcle it T h i rtt h r i-r specics' ; :ulfur-''r' i n g

bacteriurn. $ hich is ettached to the surface oi ri navtlr lar!a

and u'hich itscll'corttairls a parasitic biicterium' Fungi as''"i-ated u,ith plant roots (nrvcorrhiz-al fungi) often contain en-

dosl mbiotic bacteria. as ri,e11 as havinc bacteria 1ir ing on their

surfaces (see PP. 6-t-t--t6).These phlsical associations can be interrnittent and c"clic

or permanent. E,xarnples of intermittent and c}'clic associatitlns

of microorganisms u'ith plants and marine animais are shorvn

28.3 Microbial lnteractio.i 579

r$v \rersus Environment

The ternr "microbial ecology"' is nor used in a gcncral *'av to describe

the presence and contributions of microorglLnirnls. through their actil'-ities, to the places uhere they'are l'ound. Studtnts of microbiologl'should be a\\'are that mr-rch of the intbrnration rx microbial presence

and contributions to soils. \\'aters. anrl associittions *'ith plants. non de-

scribed bl this term. u.ould havc bL'L'n con\iLiL-red as "enr ironment:rl

nricrobiologl" in the past. Thornas D. Brock. rhe discorerer of Tlu:r'ntus utluaticus, rvhich is kno*n the ri'orld o\-r as the source of IarT

pr:rl1'nrerase for the poll merasc chain reaction r PCR). hl.s civell a de t'-

inition oimicrobial ecologl'that n3\'be useiui: "\licrobial ecologf is

the studl' of the behavior and actir itics of nricr.rorganisms in their nat-

ural environments." The important operator in this sentence is r/reir en-

vironment instead of lle environnrent. To emphesize this poinr. Bro:kha.s noted that "microbes are small: their environments also are small."

In these small environments or "micr<xnvironments." other kinds ofmicroorganisms (and macrcx.rrganisms) oftr'n also are present- a critical

point that w'as emphasized by' Sergei Winogradsky in 19'r.

Environmental microbiolo-u1'. in comparison. reletes prir:i:iriIr t,r

all-over micrc.bial pr(rcesses that occur in a soi[. \\ i"]ter. or tbt.d. us er-amples. It is not concerned u'ith the ptnicular "microenr ir..nrnertt"*,here the microorganisms actually' are tunctioning. but s i15 15.'

broader-scale effects of microbial presence and activities. Onc cair

studl these microbialll" mediated prL)cesses and their possiblr' globaiimpacts at the scale of "environmental microbiologl " n ithout ktxrrr -

in-s about the specihc microenvironment (and the or.-si.rnisnr. t'Lrnu-

tionin,q there) s-here these pr@esses actually' trke place. Ilorr cr er. it

is critical to be aware that microbes function in their localizeJ cnr i-

ronments and affect ecos),stems at greater scales. including cuusingglobal-level effects. In the last decades the term "microbial -.ol()S)" \largely has lost its original meaning, and recentll the statenrent h:rr

been made that -microbial ecology has become a 'catch-all' teiin." -{syou read various textbooks and scientilic papers, possible ditlerencesbet$'een "microbial ecology" and "environmental microhirrlogr'"should be kepr in mind.

in table -Z[1.], Irnportilnl htltt)lin !ii\L-li\L's. 1:i.,!1olnS listeriosis.rnalaria. leptospirosis. legioncllo:i:. atrd \ itinosi: alsrr inr oir csuch intcrrnitlent and c) clic s) mbiosl\. ThL-i. tliscrt:c': ri ill htdiscussed in chaptcrs -19 and J(-). Intertsi:;tg perrllan.nl relr-tionships also occur betrveen ba.-teria lnd riiliitttlis. a: shori n in

table 28.2. Hosts incluclc sqLrirl. leechcs. aphids. ncnlaitrdi-s.enrj moilu-.ks. In each of thcsc'clr:as. un ir:rirortant Cl-rri-aJlr'rt.-

tic of thc hos{ llnintli i\ conierred bv the n.'rttlancnt h:1--t.riaisvmhionl. 1

Alth0ugh it is pt,..ihi.' li) ()i\cr\a Illt-a\!\)r!.tr::.1:.. ::l lit-'tvaricrJ pirl:iiel ass,,.i-rii,rti. ',r i'.h i'iilcl L':--..lli:lli\. lilL- l::-l iii.ri

therL'is \(rmc tYpe 01'phrsical coniact pror ii;. tltr ir:it'rltt:Ii'.rtl t'nthc lr 1ri'. ()i' inl.racli,)it. til:rt rrliSi:l l.c t,:ii:-inS. T1':c': iililrr,i-tirtnr incllde ntutuali\nt. ;trqrpgr'.r'.ir\n. !L)rttitr-'nsalisnr. !-rciltitrn.parasitirnr. un)enslllr\rn. ilnd .orrlcc't;tiott , tigure 2!i.l:. In llriscp3n. thJ\ \\ L'rc f-ir\t tic:e ribetl ilitd rle f ined 'c;' bioit,rgist: :turil ing

Srmtrimis H6t Cvclical Svmbionr

Plant-bacterial

l\{arine animak

Gurncra (tropicalangiosperm)

Azollalrict, paddy fern)Pruseo{us (bean)

Adisia (angiosperm)

Cmal ccle*tcrares

I-uminots fishSquid

.\'os;,,c i Cr anobaaia:;un )

Anubatnu 1r\ 3lr\r-.. lrriunl !

Rlii:.rtitiu.nt i \. llrg: .

Prtfi tb.tL lt t iiqt:Sltnhiro!:tiut:

{ dinillmari ir'rtl ,

llhrio- P ltoit,i,,r. :. ., :,'rPhrtnit:;:t ri:t,r: ;: ':, ,t

AdaFed 116 L $*frrtis std lf- J. at lrua 1998. Erd*;.,mbios: Ct.llal anJ rtr.rt.r in c\

\Eri@-Treadsin,rit al,i,t og; Atf32--46,t bles I,Zaei3.

Examples of Permanent Bacterial-Animal Symbioses and the CharacteristicsContributed by the Bacterium to the Symbiosis

Animal Host Svmbionl S!'mbionl Contribution

lntermittent and Cyclical Symbioses ofMicroorqanisms with Plants and Marine Animals

Sepiolid squid iErpnrrrrrtt scolttltts\l\'ledicinal leech I H i rudo med ic i na I i s\

Aphid (Sclu:nplt i s I rlil i tl um )

Nemattxle *orm (lteterurltabditis spp. t

Ship*'onn mollusk (Llrorhs pedlt ellatus i

Luminous bacteriu'Enteric bacteriu m ( A e mn n tuts re ronii)Bacterium t B uchne ra aph id i colalLuminous bacterium ( I '.otorhabdus luntinescens)

Gill cell bacterium

Luminescence (\/i b rirL -fi.t

I t t' ri :

Blood digestionAmino acid synthesisPredation and antibiotic s1 ntherisCellulose digestion and nitrogen fixation

crobiolog). \\'L\hin3on. D-C.. ll7--l I- ablc I

lnteraction type lnteraction example

Mutualism

Cooperation

Commensalism

Predation PredatorJ\e ->

Parasitism

Amensalism

Comp€t,tion

One outc$mpetes theother for the site's resources

^ a !.-____--__A.-}4E

\J

-Both coexist at i"c:yer leveis. cue totheir sharing the limiting resource

Figure28.1 llicrobial Interactions. Basicchareitclr.ii.:.,isr nrbiotic inic-ractions that can tx'cur betr'* een diftcr.-nt ()r!r1i'ri.nt\.

piants. aninrals. and easilr ob:cn ahlc nicrobill :r:scnri-l:,ri..H. A. deBarl's uork u ith lichens is an er--ellcnt e rrirttplc.

'I . Define the terms symbiosis and microbial ecoiogy. Ho,,'., are

they similar and different?2. Define the terms population, communit\,, and ecosystem.

-1. ln what ways can different microorganisrns be in phr,sical contact?

4. List several important diseases that involve cyclic and inter-mittent symbioses.

saG Chapter 28 Microorganism lnteractions and Microbial Ecology zo4

/-----7 prey

(__S**

\Iutualisnr ILatin rrrrrrrrrr.r. lrorrnuc'cl or reciprocal Idefinc'r tit:rci.,iirrr)ship in u hich 5ir111g pggiprl-i'rcal bcnr'f it lc(-ru.': to b.'::r

Iriiriilirs. J-hir i. an ohliSatrrtv relatitrnslrip in rvhich thc nrutual-ist rrnri tirc ho.t are nlctuh()licalll'clepcndent on c-ach othcr. \\'hr':t\c|.rratLrd. in nrenr cascs. the rndit idual organisnrs \\ ill not \u:-vir e. Sevcral e\anrplr's of rnutLlalisrlr are presented next.

Microorganism-lnsect Mutualisms\lLrrullistic r-issi)ciuti()rls are conrmon in the insects. This is rclat:;to thl iirods used bt insects. rvhich oticrr includc Irlunt siip or ar',i-

nlil llirids lrckinq in esscntial vitanrins and anrino acids. l'hc i-.,-

rlulr'.J \ itartiin: :.rnd anritto acids lire provitl.-d hr bactcri;r\-\ nlirronts in erchange lirr a secure phi'sical habitat and anrple nl.,rricir!.. The aphid is an c'rce Ilent exanrplc oi'this nrutualistic r.'lr,-tirrnrhip. This insect cclntains [Juclurcru rtpitilicttlu in il.irtopiasrn. anJ a rnature insc-ct contains literalll nrillions of the':brrit.'ria in its kxJl'. The Buclttrcra provides its host uith anrin.rricids. particularll tryptophan. and if the insect is treated rvith an-tibicrtics. it dies. I1/o/1-rrrt'ltiu ltipietttis. a rickettsia. is a cvtoplasn',i;cndrrsvmbiont tbund in 15 to 209t of insect species and can Cofltr-trl

tii.- r:prtiducLi(rn of its host. J'his microbial association is thouSr:t() i1a il nra.ior tactor in the el'olr-rtion of r -'r :r.r.l s, e - ia.,or. ir. .1.-

i-irl::iii! rr usp:. II?r/lrzrr'1rirr ul:o cun c:.lusc cvtoplx\nric ine (,ntptr::-rililr in irt:r';i:. parthcn()SL'nesis in butterllies. antl the lcnriniz.-t.i,r. ,,i SCn.iii nrales in i\()p()ds. \\'hat could bc Ihr- adrantasc ti,,.i-': \il,lltti'ltitr ' Br limiting sexual virrirbilitt'. thc blcteriunt rliS'i::i-'rnclli br e rc.iting a nt()rc stablc a\L'xLlal enr ironnrent tbr it\ o\\ ili,,n iL- j'-lcrril li:;irrtcnancc-. Our undL'r:trnding of rricrobe-i nsc.-t

:ruiLi-rli\nrs. il;luding thc'role ol'lIi;lDirr'lirir in irt.ects. ir;,.;-,-.lrrir'il\ .\Funiir:l u ith lht incrca:c'd u\c of molL'cLtlar techniuuc:.

-l-irc 1-1'.,11,;,111n-terrtritc rclationship ir a clus'ic e xantirlc ,,:

.' .:::r,,li.lr ir: ri hich tlrt ll:r:.:lllitcLl pr-(-rtrr./()ir lir e ir iirc .-gul lJi t.:;..;t:. ::n.i rrr'.,.i ro::cltc: tfigure 28.h\. Thesc lltscilutcs criri i,:,

. .ii'-t t.i'c:iri'.'h,rdralc\. iicquircd us criluloic inucrt.-d h'. thcl:t: ,-: ll_lLtri 1..11:). I lt. lr()tr)loi.r cnrLrlt rioirtj nuriiclr-s. tiirc.:i:ri .rllui,i.c. urd nrct.ihtrlize it to acctalr'anrl other L)rodu.t\.-fa:-r':rr,-:' r.ridizr llic uccta!c rclca.ed b_i thcir lluscllutc'. BcclLuse ti::ir,,.t I' lilnro.l al*'ar s incapable of :r nthesizing cellulasr's (cl/\ nri\ thul cr:lLIVsc th.- hrJrolrsis ol'c.-llulose). it is depentie r:\,:1 i-ili nr.rtui.rii-tic prot0zoa lirr its existcncL'.

T:rjr nrutLi:,li.tie rclation:hip can be readil_r'tcst!,d in the llt,-i);;ri{)r-\ i1'*tr,'.1 roacher arc placc'tl in a bcll.jar contarnin! \\(),,*riri1.. 1,r',.i a hrth conccntrati()n cll'O.. Bccausc- O. is to\ic t() iitjll:i.:.'llatcs. thr'_r tlic. Thc sood r()ucitcs arc unallcctc'd b1 thc hig:.(). e.,ltecltlratr,'li;.rrtr-l u()t)tinue to in_cest r|ortd. Lrut thc\ soon iiic()1 \tiir\ ation duc to a Iack of celltrlases.

Zooxanthellae\l:Lnr ntrrine inrertebrates (sponges. jclll'tish. sea anenrone:.e orril.. ciliatc': r harhor endost'ntbic'rtic. sphcrical algal ceils call.-.izoo.ranthellae * ithin their tissue (figure 28.3a t. Bccause the dc-gree rrf host dependencv on the rnutualistic alga is sonte*hair ltri:thlc. trnlr one ,'r'ell-knog n exantple is presentcd.

Parasite@ ----->

-+

.,,^:.---------------- 8 ,\_,'

/:\o

8,,

-t

o Fiost

2 8.5 M icrobial lnteractions

Figure 28.2 N{utualism. Light n.ricro-graphs of (a) a s'orker termite of the

senus Relicrr litenrtes eating $'ood ( X l0).and (b) Trit'hotttmplta. a multillagell::tr.dprotozoan tiom the termite's gut (x I-l-i).Notice the rnany flagella that occur trrernrost of its length. The abiliq ol Trit-ittt-tttrrtphu to break do,'r,n cellulo5g iillorvsternrites to use wood as a fbod source.

{a) (b)

Figure 28.3 Zor-rxanthrllae. (a ) Ztxrranthellae igrc-en t u ithin rhe tip of a hvdra tt:ieclc i .; 1-i()) (b) The green color of this roreetrral , 1/ruiiliirlt i. due to the abundant z,ooxanthL'llae *ithin its tissues.

'l i:r it,:r';:trrtrpl- rl.s1l-[llildinei cirrals (ligurc -S.i/ri :liii'i-'iri{r\i (,: tht:r cne r:,r rctluircrttents usins thcir l()()\l.inthal1.ic. P;iiIcnl. ar(\i,.i-,:.i irr thl u()rrrl pr()tcct thc algae frtltrt thc hltrtl,iulc11c.i. ii1- r-rll:-lrr ilict rridiltion. Clearlr Ihe zor,rlrtiitcllae :rl.rr1...'r::ll llrt' .,'r-itl tr':,.iu.e the calcille uli()n r:.ltc is lrt l.-ust l0 til:l::!r..rlui irr tl.ir irgirl ihrrrr irt thc dtrk. Hcrntatrpic c!rrrrls lx.l.inr/!)(\\ilillire ll.ri hlir.'l r crr. los rate o1'calcitlcatiolt. B:r:ctl ttn lhrr'it'

\ilirl. aurb(,n j*1rlrrpic crrrnposition. it has heen dcterrninr'd Iirat

nr\)\l (,1 the i,rllini.'curhon in thr'tissue: of the hcrntatvpi! e()rel\llrs uornc 1'roir thc ziroranthellae. Becnusc of this corel-algal nru-

tLrlrli.tie rclriti,rrrr[iip-c:r|lpt;jpo. crrrtra-11 jp-o. lnd crc]inq nuirt-inlr urrJ cncr:-) !(ri-al rcL'1s are iinl()nS the nlost prrrdLrctir.e lnci\uauc..tLll ot'kn0$ n ec()s\ stems.

Sulfide-Based MutualismsTube u'orm-bacterial relationships exist several thousand metersbelow the surface of the ocean, where the Earth's crustal plares

are spreadin-e apan (,figure 28.4;. Vent fluids are anoxic, containhigh concentratilrns of h; Jrogen sulfide, and can reach a temper-ature of -3,50'C. The sea\\'ater surrounding these vents has sulfideconcentrations around 2-5C pM and temperatures l0 to 20'Cabove the normal seawater temperature of 2.1"C.

The eiant (>1 m in len-gth'. red. gutless tube worms (Rrfiaspp.: figure 28.5a t near these hydrothermal vents provide an ex-ample of a unique forrr of mutualism and animal nutrition inwhich chemolithotrophic bacterial endosymbionts are maintainedwithin specialized cells of the tube worm host (figure 28.5 b.c.d).

\

5$2 Chapter 28 Microorganism lnteractions and Microbial Ecology

Figure 28.4 Rasic Structure of a Hl.drothermalinciLlJinq :ult'i.-it tra rL'i.il\eJ lls \e3\\'ater penetrates

crL'aIing L'uvir()nrlteni\ tirr -crtlu.th of the tube lvorrns

Ir, .i:rrt eli ltlcmpt. io cltlture these isolated bacteria-likc or-

gllil,:.ir: i.ilii c i.':ctl tln\llaaa\\iill.J'l:: tLrl.l ,.i(rnri i.ii.\ up itrtlrogen:ultltlc irtrtrl thc \ca\\lltLrr

anrl i-.iild\ it 1rr h;litlrlrrhiri ttilc rea:Lrn the $orll'ls are bright rcdi'l-hc hldror:cn 'ultide i. thcn transPoned in thi: lirrm to thc bac-

tc'ri-. rlhici-r r.r\c tlrc \Lllfide-reducing pou'er to llr carbon diox-itl.'ir thc Celrirt r. cli (.,t'r' ligttrt' 1{t.1). The COl required lirrthi: ire lr is t1'r1r1>p(rried t,) the bacteria in three $'a1's: freell dis-

solretl in thc t lot-,ti. bound to hen-rogiobin. and in the tirnn ot'or-garic aci.ls \ttch 1: tttalale and \uccinate. Thes.'acids arc

dL:ciri-h()\\'liiie il t() rclcuse CO. in the trophosome. the tissue crln-

tainin! Iracicrtal \\ Il,r':i)itl\. Using the:e mechanisnls. the bactc-

ria l\ ntir.\ilc lcr.iuccti ()rganic nlaterial fronl inorganic

sub\ttnce\. Thc o|cani- ntaterial is then supplied to the tLlbc

\\'()rnr lhroush its circulatorv svstem and sen'es as the main nu-

tritional soLtrcc for the tissL' ' cells.

A .inriIur nrutualistic relationship occurs in Ridge iu pisc'c.tttt'.

I tuh,c *ornr lound in the north.astern Pacitlc. This aninlal rnain-

rain: its cndosr nrbiotic sull'ur-oxidizing bacteria in specializccl

tissue :. sinrilar to the nutritional strategv of Riliirr.

\-ent u'ith its \Iutualistic )licrobr-.{ninral Associations. Reduced chetnicalsthe fracturetl hlsaltic,)ccr,l li,,,,.- :' itr'lrtct1. irttti returns r\ \'ant lluiil to thc- txt-an.

and their procarr otic lnulr,rali.t..

Methane-Based MutualismsOther unique tr,>rd chains inrolr'e rnethane-fixins nricroorgan-

isnts as the llr.t rtci) in pror iding orglnic nlatter tor consuflrers.i\{ethanotrophs- bacteria capuble of using rlrethanL-. rru-cur as in-tracellul:rr sr nraionts of methanr'-r'ent mussels. In these rnussels

the thick fleshr gills are tllled ri'ith bacteria. ln addition. methan-

crtrophic carnivtrrous sponces have been discovered in a mud vol-cano at a depth ,ri' -1.9-1-1 nr in the Barbados Trench. Abundantmethanotrophic .r mbionts u ere contlrmcd br the presence of en-zymes related lo nr-thane oxidation in sponse tissues. These

sponges are not ratisllcd to use bacteria to suppon themselves:thel' also trap sr,."iinrnin-s prc\ to give r urietr to their diet.

1. V/hat is the l'lical characieristic of a mutualistic relationship?

2. What are irir'lrtant rcles of bacteria, such as Buchnera and

Wolbachia in insects?

3. How do tube .', crms obtain energy and organic compounds fortheir growth?

4. What is the s:urce of the rvaters released in a deep hydrother-mal vent, anci how is it heated?

28.6

hydroxides and iron silicates f.omrising vent fluid precipitate in seawater

forming white and black "smoke.'

precipitate inside vent and chimney

Seawater seeps throughcracks and fissures in crust

6.t

he Rumen EcosystemLuminants urc r gri.',i!r,,i^l:ri-b:ro1 ,r1.1.;1,;jv-r11il. ihril i:lre a \t{rlll-:h dir iderl int0 iirit: a\)nriiliiirite ili\ :1il!i .llc\\ u e ud crrnsisting tli:gurgitated. partialrr digc-t.-ri li.lo.i. Eranrplr-. include cattle.

ier, alk. calll!'l\. bur'iilr'-:1lJCi'. -!r':rt'':rnrl r:lliic: The pllrnt

ialcrill: u.td as thcir rtllritt iqrqrli:qr11;-3 il.ili!ill' .rlc (tl P.)or nLl--itionll qu;litr : lar:; i olturt';. (\l-lllri-r-lil\ ttlLi.l l-c rttscsteti ilnd

r'(\]c\:ed in thc gLrt. ir co0lrll:.riii,r': i,';llt e olttf l.:r ttritrrlhiltl eonl-

runities. I{r nrect the nirtritii,rr:ii ncc.1. ir1'lhe lt:inllrl..'\r liotrld hi\p.ctrrl. thr'Sttt in lhc.c.,tll:il:rl' i: LlrlitlLrtlr :rilllJrlgll l'rrr p;o-

--:sirtg plant lllatr-fi:r1.. Br Lr.:rll 11,i.i,,ir191i11l.itl: tt, cielrlidc lhe

rick ccllu]rrrc r,r, alls ot !fli\- .:ild ()lhai \ t'!cl:.lti{)ll, fLlnlinanl\ di-r\l \ ir\t ililt!)Llnls of itthcru i\d urtli\ lillrhlc ti)i-ugL'. Ilcultusc nt-)in!nts cannot s\nthe\irc ccllulu'cs. ihet hlrc c:tablisitcd a

rutualistjc relntionrhip \\ ilh rnacr()bic nricroorsertislrts that pro-

uce thes. L-nr)'nrc\. Cellulrrc. Itrclrllrzc the [3t l+Jt lirrkagesJt\\'r-cn \uaccssi\e Ir-!lLtco:,; rt:idrte. ol' ccllulrlsc lnd rclcasclr:cos.-. r" hich is the n tcrntc'nl.'tl to ttrulrnic acitl: sttclt lr\ aceliile.

Microbia I lnteractions 543

GillplumeGirl

plume

o2

CO,

H,S

o2

Co.H,S

HSHbC-

Transloc:'ionproducts

Sulfideoxidation

Calvincycle

Vestimentum

Circulatorysys'iem

Coelom Trophosome cell

Bacteria

Capillary

Capillary

Nutrients

Endosymbioticbacteria

Opisthosome

igure 28.5 The Tuht \\ornt-lJacttrial Relationship. (a) A comnrunitl of tubc \\'()rrns (Ri.liiti 1t.it'ltt1)tilot ,\t the Galirpart-r: Riftvdrothcmral rent.iic rrlepql l.-i-ilt r:r.,. F-lch \\orrn i\ more than a nleter in length and has a a0 cnt siil plume. 1b. c)Sclrernatic ilirrs-

menturn..{t its itni.ii(): r:tLl is ri ii.;riritt():-\ r:il1 plunre. Insidc thc trunk r-rf the uornr is a trophosonre ccrr)sistin!: primlrily ofndosvntbirrtic bacrtria. lrs:r,gilitcd .e llr. aird L,ltrrd rersels. At the p()sterior end of the animal is thc opisthi)sonte. \\hi.h ancht)rs the

lrbon c\lrrpoLlnd. .);ithr\i.,;'!j Lr ,ir. .;l1iirrr rir)i(rn1 i\ trllnsl(rrrled to thc aninlal'S tissues.

o2

co.Hr"

(d)(c)(b)

hutr rate. and pro;ritrnatc {.\('('./i(i/r( 9. /r/r. -I'ticsL'():glLnic rJii: iiri

thc' trur' enL-rg\ s()urcc' fitr thc runtiitilnt. Organic Ir:ltler []i!)ac\\-ing can cither stop at the aictlle lc-r el ()r continLle ttr forrnlnethane as a major end product. These trio pattL'rn\ of process-inr rppear lt,r he undcr genctiL' iind ph\ loScnetic cLrntroi as dis-cussed in \Iicrobial f)irersitl & Ficologl 2t1.2.

The uppc'r porti()n of a rurlinlnt'\ stonrJch crpuncls to lornr a

laruc'pouch called tire rumen ({igure 2lJ.6l anrl al:ro r,t.nrallerhonelcornb-likc rcticulr-rnr. The bottonr portion ,r1' the si.rnrachconsists of an antcchnrnhcr call3(l tha ornusurn. r,. lth thc "trr-re"

stonrach (abonrr:urn) behind it.The insolublc polvsacchliridcr and ccllulosc caten b\ the

rurninant are nrircd q ith saliva and enter the rllmen. \\'ithin therumen. lood is churned in a constant rotiirv nrriiit.rn;lni eren-tuallv reduced to a pulpy'mas\. \\'hich is partialll diqested and

f'ernrcntcd bl lnicroorganisrns. Later the 1'ood nroves inio the

reticulunr. It is thc'n rcgu|uitated as a "cud." $'hich i: thor-ouchl\ cherr'ed forthe tlrst tirrc-. Thc t'ood is nrixecl riith saliva.

Trophosome

584 Chapter 28 Microorganism lnteractions and Microbial Ecology

Organisms with digestive tracts had to make an interesting el'olution-

ary choice: rvill the microbial conimunitl' procluce methane or not?

The use of plant materials as a major firod sourcc does not alrval s iead

to methane production in the di-gestiYe tract. For exaniple. kan-qrrt'ns

do not produce methane. u'hereas sireep and cattle do. The kangaroo

has a distinct advantage in terms of nutrition. \\'hen complex plant nla-

terials are degradetl only to organic acids such as acetate' the aninl:rl's

digestive system can <lirectl;'absorb thc acids. In sheep and cattl--' the

microbial communitl is more complex and conr erts acetate-ler''-i :ub-

strates tLr methane and carbon dioride. Ieading to nutrient los: 1-'om

the original plant material. This loss can be substantial. u ith l 0 to I 59i

of the r.-rganic matter in the feed lost to the atntc'sphere as meth:rne'

An eramination of over 2'i0 reptiles. birds. and maninals

shou,ed that their nraintenance of methanogenic nlicrftrr,eanisms and

methane production is under phvlogenetic and not dietary control

(see Box figure). Although low levels of methanogens can b.' de-

tected in venebrates that do not produce much of this imp()rtant

greenhouse gas, the lack of methane production seenls to result troul

absence of methanogen receptor sites in the digestive svst!'nl. As

shou'n in this figure, the ability to maintain methanogens otten has

been lost. A similar situation occurs s ith a(hropods: nltthane is pr()-

duced by only a t'erv organisms, including tropical millipedes. ctrck-

roaches. termites, and scarab beetles. If the presence of nrethanoqens

results in u'aste of nutrients, '*'hv have so many venebrates and

anhropods maintained rhis "energerically rvasteful" process.) It is an

interesting question that relates back to the basic nature of venebrate-

gut microbial communiry evolution.

Cervidae

26.6

Dan uacaca- / papiovCercopitnecinue /\1

Galagonidae

!It1i

fdtoae - rII

r,'.. ,' TalPa

Tenrecidae r._----_._,

Caprinae Bovidae

Tragelaphinae

Choreopsis

Equidae

Tapiridae

Rhinocerotidae

Loridae

Suidae

Tupaia ChiroqteG Tayassuidae\

Dolphinapterus

----g-- rurs,aps

Trichechus OrycteroPusLoxoConta

Choleopus

Elephas DasypodinaeProcayia

Myrmacophagidae

\Iicrobial Dirersit-v- and Ecolog1. Cloerolurion of animals and their gut microbial communities: the methane choicc.

lUethane-producing \.ertcbrate s are noted rvirh solitl recl iines and roman letters; nonmethane producers are noted u'ith blue dot-

ted lines and italics.

r.\\\ rllo+ r'd. and reclltcr\ tite rtttncll rr hile atlothcr cud i: pas'*J u1l

ro the mouth. As thi: pr()ccss colltillLlcs. thc pirrrialh di"csted trlant

rnarerial becorrtes ntore liqtrid in nllture. The liquid ihcn begrr: ttr

t']ou,out of the reticulLrnt und into the louer pli.rts oithc ston,uch:

irst the onrll\urn and then the atrotttasunr. ]t is in the abtlnlasur:', that

the ltxxl encounters the host's nortrlltl digestirc ellz\nlei and th: di-gestive pr(Eess continues in thc regular manlmaliltn rr ar.

The rumen clt'methane-producin! anintitls such as eattlc criil

tains a large and diverse microbial ctlnrnlunitl'(about l(lir,'t!.titi"n: per milliliter). including procarvotcs. anaerobic ir.tn!'i :tr.iras ,\'eocullim.lsll.r. ciliates. iind other protozoans. Ftxrd entcrirlrthe ,lnren is quicklt'altacked br the celiulolvtic aneerohic prt''

carlotes. fungi. and protozoa. Although the nlasscs ol procarr

otes and protozoa are apprtlrinlatelv equal. the prt,ues:it.t': , rl

Homo

Gorilla

Giraffidae

Camelus

l-ama

28 -o

Omasum

lmall intestine

AbomasLm(true stcrach) Reticulum

Figure 28.6 Ruminant Stomach. The stotnach c()rlrplrt-

ments of a co*'- The microorganisms are active mainlv in the rLr-

rnen. Arrou s indicate direction of food molen')ent.

runren contents is carried out mainll' bl the procarrotc:. \li-croorganisms break do$n the plant material. Bc'ceuie thc ritiue-tion potcntial in the rumen is - 30 nr\-. ail indigc;r',1r.

n:icrtrrrrqanismi engage in anaerobic mL'ubolisnl. Thc hlrctcl'irr

It'ilncnt carbtlhrilrates to tatt-r' acids. carbirn clioxi.ll. al.tti il,r.:r,'-

!rn. The archaea {nrethano-eens} produce methane tC}l-rir"r:lru.atiltL'. CO1. and H1.

Dic'tarl' carbrrh)'drates degraded in thl- nlnlen include :,'l'-ri'l'-:

\Lllilrs. starch. FEctin. hemicellulose. and cellulose. Thi ilLi-gc'l

lL-rccntase of each carboh)'drate is fermented to rollilil': i.:l1r

ruids (acetic. propionic. butyric. formic. and valcric;. C()r. i{--

rn,J m.-thane- Fanl'acids producc-d b1'the rumen trrsanisltt: rir. :!b-

.rlrbcd into the bloodstream and are oxidized bl the anilrrrl :r' ilrnrain source of energ)'. The COl and methanc. produicti lli l l".rte

oi ltXl to -100 liters per daf in a co*', are rcleaseri hr '-rttcl:,l:ottI,l-lrtin enrt'turc. to ht'lch]. a continuous. scarcell eudihlc icl;crprL)ce\\ sinrilar to roLlching. ATP produced during tcrnlclllirl;,'rl r\

u\rLl to \upport the grou'th of rumen nlicrt,organitttt'. -l-ht>.: llli-cr()organisms in turn proiJuce nlost of the I itlnlins nc'!'d.(l b\ ih.runlinant' In the renlaining tuo stomachs' the nlicr' r( )iq'rrrl\rlr\'

h:.ir in. performe.J thcir s1 ntbiotic lask. are digr-stcd to r itltl r,::lIil"acids. sugars, and other nutrients tirr ruminanl use.

Cooperation

Cooperation and cotrlnlensalisln are t$o f\)5iti\c btti lltrt ol'll:rrtor\ I\ pes of sr ntbioscs tirund ri idc-lr in thc nlicrobial rl, '; 1i.1.

J'hese involve slntrophic relationships. 51 ntrophisnr IGreci 'rr;.togcther. ant) tntplte. nottrishment] is an a':ociation in u llie 1-r thr:

tirr\\.!h ol one organism either depend\ Lin or is inlplCrc.l ltr

gro\\'rh factors. nutrients. or substrates pror ided br rnothr-r or

ganism grou'ing nearh\'. Sometinles both c.rgiinisnls hent'l'it.

As noted in ll.,ure 2E.1. cooperation benefits bt'tl.i ttticrLrot -

sanisms. but this relationship is not obligaton. Beneflcjal cotrr-

tr,iroJen \.----l\ /fixer i \

,/Azotobactei / \tuvtv@elatt /

\- ctucosei

N2

Microbial lnteractions 5a5

coa

H,S

Light

ChromatiumDesulfovibria

//+NH4'/// \t

/\tl\tl.riroSen \.-r--l\

(b)

Figure 28.7 Iiramplcs of Cooperative 51 mbiotic Processt's.iarThr'org:rnic nratler (O\1 ) and sultate required b,v Dcsul.fovib-r.il are prrrdu;ed b1 the Cltrtnnatiran in its pholost'nthesis-drirenr.riLre tir)n o1'CO. 1o organic mattc-r and oridation of sulfide to sui-i;.rl'.:. i tt I .-\;1t!rltLtc-t€r uses glucose pror ided bt a e cllult,.t-.i-:::i:-rrlitt! ir::i,xrrg;ritisrlr such ltt Ccllulomrtrtri.t. u hicit tt\cs lhL',,:trorcn Irrc.i h1 .\:otoltot !t'r.

;lcilrcntarr r.>()urces are provided b1 each of thc paired rIi-!t'{)()rqallislr\ -flrc irrsanirrlls irrr.olYed in thi\ t\ pe 01're iliti0nship.en he scparatcd. anil il'thc' resources pror ided b1 the corttplc--

rlcntan nici-oorganism are supplied in the sro$th enYironnlent..ilih nlie ro(rrSanisrn ,,r'ill 1'unction independentlr. Tu'o cranrplcs

',; thi: t_\ pc ()l rclatiortshrp :rrc the as\(rciation ol I)cstrl.fttviltritt'.\ril C.'ltr()nttilllorr {tigure 28.7a t. in u hich thc carbon and sult-r.rr

.\ clL-s arc iinkcd. and the intcraction oi a nitroSctr-tlrin:: rtri-

ulrrrrr-irnirlir "i

itlt li e e llLrlrrlr tic ttrpanisnl such ts C.'tlltrlrtrrtttr:rt';, r i!,.rrc lS.-l,,. ln thc sccond exarrtple. thc ccllulose -tlcuradinS

iriir..r()ilrqani.nr lihcrltc: glucose fiont the ccllr-rlrrse. ri hiclt can 'oe

ri\a(l h\ nitrrrrcn-t'iring tnicrobes..-\n crccIlcnt crlinr!lc of acoopcratire biodegraclatirc associ-

ririon ir slro,.i n in {igure 2fl.tl. In this case i-chlort)beilzr)r1-.ilsradatitin dcpe nd. i,rt thc functionin-c of nticrtlorgani.rlls rr itha()nrplL-nrcntlrr caplrhilitic-s. It'anv one ol thc- three tnicr,r)r!rtll-i.ntr i: 11()l present and actiVe. the degradation o1- the subslratc\\ ill not ()ce ur.

\":::)(a)

5a6 Chapter 28 Microorganism lnteractions and Microbial Ecology

Desulfomonile tiediei

3-chlorobenzoate\\\*.,//

MethanosPirillum sP.

Figure 28.8 Associations in a Defined Three-IVlembered

Cooperative and Commensalistic Community That Can

Degrade 3-Chlorobenzoate. If any member is missing' degra-

.iation $ill nor take place. The soiid arro[,s denronstrate nutrient

tlo* s. anci the dashed Iines represent hyp:the :i :d ll^n '

l l otirc r . urpcra!i r c relations. .ul f iclc-drper,.1g11i 3Ll11111 oirh i -liii.rll.nt()u5 rnie rot,rgunisltls tlx carbttn ditrridc lltd sr nthc;iz-c-

()i-I11tlie ntal!ai thtt :e r\ cs as a carbon and energr s0ttrce ftlr ii ilsi-

.r ()'rr()piric organisnt. Solne of the ntosl intcrcstillg inclucle thc

pirl'. chrtc'tc \\ ()rlns .'\lt'inella pontpejatru (figure 2tl'9t' thc I)orn-

peii irtrnrr. :.,rrl ltlr,, PLtrulvittellu Pttlrtti.lltt'ttti.s, the Paltll ut'rrn'

il,,ih ir ar c tl ;l:l lc tl i, , Ll. bae Icrilt oI) the ir dorsal :r-trl ace-' ' l-hc:e Il l-

28.1 0

Figure 28.9 A N{arine \\brm-Bacterial CooperativeRelationship. Alt'i'telltt potnpejana, a l0 cm lon-s worm- forms

a cooperative reiationship u'ith bacteria that grou' as Iong threads

on the \\'orrn's surface. The bacteria and Alrinellu are found in'unnels near lhe black s.-roker-heated water tonts-

ilnrent()ri. hecrcria can ilileralc high lerels of rn.-tals such a-s ar

senic. cadtttiurrt. uttd copPer. \\'her, gro*'illg ()n thc surl'ace ol thL

aninral. ther nlir prorii: proteclion lrom these toric nielals. a'

',rcll lts thcrnlal pl'()lL'cti()n: in addition. ther appear to be used a'

il tilod 5()urcc. -'\ dL'eP-\aa crtlstacean hat been discolercd tha

u:e,s suli'ur-oridizirtg ar-riotropiric bactcria as iis tbod source. Thi

.1rrrrill.-. liirirrtrrrr.r ('.\i)'-itl(tt(t ttigurt lll.10r has tllamentou

p/s/s'iSr

I

I

I

s's,EI

Figure2g.10 AltarineCrustacean-IlacterialCooperatireRelationship. ra)Apicture,-rf thenlarineshrinlp Rintir:urisetoculutu

thi. t1-rirt SCill'ri1.

>-..S\*-\9o'\%\"6

58728 11 l'vl icrobia I lnteractions

Figure 28.'1 1 ,\ \Iarinc \ernutodr-Ilacterial Cooperatire Relationsliip. \Lu-ine i.ru..-li:'irr IiJ;i:r,i,,11;'.. \\hich :.:rtrrr at thc

(b)(a)

-LrllL:r.-rrritl:,:irl.t b.,-al;-ii !rr,,r 1;;; ,,;l ii: :urlace (trgure 18.1i)hl.\\-htir therc rrc t1i-i.,.j-lc,,i ilrr .hli irt:-r ingr--sts them. This ntlrni-nuilr "blilr j" .h"ii:rl !:,1 1-J\ii, iri !,, iir: Slou r'mitted b1 thc bllck\:il(riii'. t-t.:l! l, l,li-:J-i:"r (ri'ii.:il r,ll ils hack. ThL'()rgan i\.1-ll\i-ii..r'to l iishi r'.iirtllltlih lil.1'! i: tt,rl tlct.-cteble bv humans.

.\nolire: intcrc:i:r: c\unrllla oi brictc'rial epigro\\'th is shor"n br

ncnliiode\. in;iudin: Etittt:tririrtt' l)uru:iti.f(ru.\. that lire at the in-

tcrliraL- bL-i\\cJrl irr'ii,5i. llll!..rllit.roiria sulilde-t-ttntainins n'lunnr-

:e.ilnr.-nts tfigurc 2E.1lri,Dt. -l-hr'rc animrls are covered b1 sultidc-

t i;.lizing b,ectcrilr iililt .rre ri(\.nt ir, intncatc- pafierns ttigure:\. 1 1 /) ). Thc b:rctcrii ni)t r)nl\ tir'.rcirrc ler els of toric sultlde. rl hich(1itdn \Urrcr,-rnLl thJiteillltode:. irllt th!-\ llso sen-e as a t-ood supplr.

In I 9!)i r. hr t1r,,',i::r-nlrl 1 3 . \\ r-i'i Jr:covered in a fieshu atcr

cni ilrnrnciri. at titi''t:r.rttonr oi L-lrke Ueikal. the oldest (15 million

-\u-ar': oldr rntl iir'c'p::rt lakc in ti.- uorld. This lake is located inth-r far cr\i ()1 Ru..i:r rfigure 28.1kt.h.cl and ha\ the largest vol-ur,-re ol'an\ ire sh\\ rtcr lakc (rt()t litr 'rrgest area-\\.hich is Lake

Sup.'r-ior). Thc hlcterial gplrriih:. uith ltrng r"hite strands. are in

th!. ecntL-r r.r1'the rr-nt f ield ,,ihc'rc thc ,righest tclrperaturcs are

ior,rnd (t'igurc 18. I li i. At tltr- .d !c ()t'th. r ent tlcld. ri here thc \\'a-

tar te rrperrti.irc i' liri.er. thc brite rill nrrt ends. and sponces. gas-

trlirlils. rrr,l otlie r . rrgirlli\t11.. ',r lliilt :. .i tit: :uliur-rlridizing

bactcria 11 1 |irr,11 11 ,r.;;---

though le ss cicr.l(,i).dLake. \\"r'e,nrin!:.

A hr r-irogci: .Lliil,i.: ',.rrt.i '.'a, !\-', \i.ll'. lr.r\ h:iiil tii:.'ilr crc.i tti

Southem Ri,ttt:rltili titui i- -1',.:r tirl,:rr- [--l::l:: '.tl:1ii-C. (-l',es ili thc

area contlin n1li. L)t nii-lL,or!nr.ti:ilr iirili i:\ cirrh()n dioxidc'u.in!h) drogen sultlde ls lhc .1!-ctron 111 )n\lr. Fon-\ -ci-sht sp-'cic-s of car t-ldrptcd inr cn.'5:-lic: ilr. \ir:i iri ld(l rt \ iit i. jl'rc nl()xLrt\ ltr!'lrhic b]:a.

.-\ ittfill ()1'uil{)ll(fil'rir,ti iri.r} t}-.i-:t': ril;:ir li it(}pLlliilir)t) (]l'.int-ilar nlier-tltlrsLrli:rll: Ill,,-rii()i\ i:. \,\\Ii r:.'ii.itr. lhc procc:r o1'

quorunt sat)sinS. r', itich ri ir. tiirJl-i..r.l itt .r--iiolt 6.-<. l'ire lrticrttrr-canisrts produ!'a specilri iliri(rin(iuaJi-c(,il)1 )Linii\. lntl ar the 3rp-Lillriit,il incrcli..' trnti litc !!1it!aiililllir,:-r,1 liic.r'.irlltPirLinJsrcacha\ criiical 1r'rel:. .rrr.iiit i-rJs :i:r .\Prd\:ci.I. l-lrcsc rc-

spon\cs llrc intn\)rltint l\)i illi.l-r)(\iL:inisn,. ihitt lirrnt lrrsociatirrnr*ith plants antl ininral.. lurrl Iliuli.ulxr'lr 1,,; hunran pilth()!cn\.

\1-rcorrhizai t fungal-yrlerrt r(ii)i intcr-:lalir)n\) prc\cnt u \pe-cial casc c.rf a ci,opcreti\ c lL-ilili(rn.hip i .3s- chapte r -1() t. "\or-Inal" chlorophr ll-contrrinrnr Ii1n1. i:.;r --rr,)\\ $ ithout thcl'uncus. plrrticularl\ in the rlee nhLru:e . in.licutins thiit this is notan oLrligat()r\ rc-1:rtion:hip. Sonrc 1unqi. ln contra\t. d() n()t sur-rircuithoLttLrJil{u.\().ililttl ',',;ti,lrIi.1',1 l-hcu.lll',tlirirrlloLi:

i. l::-' j)re \-: ji ,ll:::r lr 1} ,- Silrtilar ;"ri-

lirclL: hrr t ir.:cir lr)un!1 in Ycllou'slcrnr'

l-

FrolikhaBav

Lake t'

5aa

(c)

Figure 28.12 Hrclrotliernrul \ent l--eos-rstems ilt l.'resh*uterEnvironntent.s. Lake Ilrikal r in Rlr..ili r lli: hce n tirunti ii, irar clo* tentperliturc hvdtort-:rnrlil r.r'tt\. t:l) l-ocutiorr oi L,lLkc

Blikal. sitc oi the hr drL'rhcnnul r:nr ilcld. rb r lJactcriril nriinear the ccnt:r o1' thc ...n1 tie itl. rc r Iltrctt'riul lllurntnt. unrlsPt)nSes at thr- adsC o1'tit.: rcnt i'ititi. /iri.\,/t//i. l)riiti tnttrt tlit\'.rri, t:.tl C, ,,r . . ' \,,

Chaoter' 28 lilrcr-oorganism Interactions and Microbial Ecology

5.

28.1 2

monotropoid plants (scr, 1t. 656). horvever. are dilt'ereni. Theseplants depend greatl), on the llycorrhizal funeal net\\,ork ro pro-vide nutrients "taken" frorn other chlorophl ll-containinS plants.

1. What structural features of the rumen make it suitable for a

herbivorous type of diet? Why does a cow chew its cucj?2. What biochemical roles do the rumen microorganisms play in

this type of symbiosis?3. What is syntrophism? ls physical contact required for this rela-

tionship?Why are Alvinella. Rimicaris. and Eublstric,tus good ex::r.lplesof cooperative microorganism-animal interactions?Where is Lake Baikal located, and why is this unique rr iermsof its microbial communities?

6. Why do chlorophyllous and achlorophyllous plants have differ-ent degrees of dependence on mycorrhizai fungi?

Commensalism

Commensalism ILatin (.)//1. to-sether. atrcl nlt,it.rl. tab]r-l i: u re-lationship in u'hich one sr,nrhiont. the comnrensal. :;nc1rr:* hile the other (sontctinrcs callcd the host) i\ naithe r hrir;::e.i norhclped. as shou n in tlgule lS.l. l-his is li Ltnitlirectionlil r:,r.-cs..Otien both 1't- ''a' t I t,' Il,- r rit- l. 1,.,1 r^i. ti. ihc \...1.. : 'rla."

I-hc spatitl prorintitl Lrt llie tir() put-tltci'\ I.tl-;lits the .:,:t-.ilr'rr-.lrl ttr lced !)il \ulr\llnae\ altJrtLrfaLl t,r'iri-9c:i.:.1 br tite i:,.i. llnrithc comntenial ol'tcn obtair.r: shcitcr b-r Iir i:t:: tithe r,,n ,.: :n thchost.'fhc- corr-intcrr:lil ir not dircctll clcpenclr.ni ()n thc lt{,-: ntflli-boiicallr and caLlsL'\ it no palticrrilir lrlrnt. \\'ltcn tite e()ii-..1-iJnslli: separatc'd iront its htrsl cxpcrintcntlillr. ii crr|r :rrrr ir., ... ititi,itlhcing pror idcd sr-rnte t'rctor or f iictttrs oi'Ittrsi rr; itin.

Conrnrensalistic rclatitrnsliips [.etrr c.-n rjti.l-,,, ,r -!lLir

- . ,: iniludt sitr.rations in *lti.:h titc \\11.ia pr()rlLtet (r: Lrit;. nliLl{.,.'i.rtri.i.,ir thc subsireir'tiri'anrr:hi.r sP.-i::'.. L)lt-: tt,,,.i U\-iiltIle ;. :t.::iii,.,,-lrrrn. thc oridatton ot arrtn.l(rrtiurri ir)n t() ltitritc i.) nIri,,,,--_.i:l\nl.:uch 3\ \tilrut:otttoiltt.r. lrntl thc \!b\cLilrcitt t,tij.:iioi.r ()l-riJ lltlriicIr)nitrJtehr -\'irrzrlrrrr'llrantl siltillrhuetcrill t..r-t i)lt.7r.\-.'-,r..\;,inrixtcter henctlts 1rtln; ri: lrssiit iull0rt \ itlt .\'rlr|r,ri?(/,f :.r,.\ ^l!]U\eil Lr:c: nitritc ttr obtlin rncrS\ lor::r'truth. ,-\:C-rriiii e rlintl.: ,,l tltirtvpe ()l'relationship is fbund in .rn:ierobic ntL-tilunr)lcriiu =-,,\\ \-lc'rtt\ SUCh a-s sludge digesters (.r(,(, .\(,('/1r,i 1 ltl./r r. lLr.ttrcrol-l: il-c'slt\\ atcr Jquiltic seditttcnt.. anrl tlootle rl :cil:. ln tirc:c e rrr ir,,..-lr-nls.iuttr acids cun r-+ dcsnrrlctj ttr jtr rrrluce H. antl iltcthuna ir.. :ltt in-tcnleti()n o1'trrrr rlillcrcnl hltetcrirrl tr()ups. \lc,titane protlii.:r.,n brnlcthanogcn\ dtpcn,.i. t,n interspecic.s h-r'drogen translcr. .\ lcr-nle ntati\ c hactcriurn !ancilrlc\ h\ !ln,gan Llis. i-inLj thc rilcLi:..:,.r-gcr;tr:es it quickl-r J\ lt \ub\lrillt' lor-ntctiilute -!lt\ irr\)LiLlctii)n

Various terntentatir c bactcria protiuce i().,\ ntol!.e ulr:r '.', JiSlttlattr acids that cltn hc desrailctj [rr lnucrol-i. hticteriu -:.ait ir\SvtrtroltltohaL lcr io produce H. a: lirliou s:

Propionic acid + acetate + CO. - H,

St'tttropltobut'Ier- uses protons (H - + H- J H. ) as ternrinal elec-tron acceptors in ATP synthesis. The bacterium gaini surilcient

(a)

lyrt4-.fotdW'gl-ttvt re4

1f,r.,lM \

{..*"L\v W)*t<rv' 1/h!4/wWLA-V**tniltt-X,tr,)

'J'--

8*ltbp"t *yenergv tbr grorvth onlr u'hr-n the H. it generiites is consunle.l. The

products H, ancl CO- are usecl bv tllethanogenic archaea te.g..

lvlatItatutspi ril/trrrr) a: tollou's:

-lH. + co, --+ CH.* + lH.O

B1 s-rnthesizing Itrethane. Mellrttrtrt.tpirililrrrr ttraintlitls a lt-q'H'concentration in lhe ilnnlediatu- enVirotttllellt of htltll bacteria.

Continut'rus rentoval ot'H. prornotes furtirer fattl' acicl f-r'rtllentil-

tion anci H. production. Because increased H. production and

consumption stimulate the grorr,'th rates of S.t'ilIntpItrthttttcr- and

il[ e t hu n o s p i ril1rorr. both particiP]nts i n the re lationsh i p br-nefi t.

Conrmensalistic associations also occur when tlrle tlricr,rhial

group nrodifies the cn\.ironrllent to make it tllore suite,-l for lntrtiter

organism. For eranrple. in the intestine the ctrtt-ttt.ttltt. nollPathouellic

strain of Eschericltiu trrli lives in the hurnan colon. btlt ltlstl srousquite u'ell outside the host. and thus is a nprcal corllnletlsal. \\'hcn

ox\'-qen ir used up bt the tacultativelv anaertlbic E. t'ttli. trbligate

anaerobes such as Bcrctentides are able to Sro\\' in the colon. The

anaerobes benet]t tiom their association uith the host and E. toli.but E c'oll derives no obvious benetrt liom the anaerobes. [n t.h;s

c&se the commensal E Cr.,1i contribuies io the ri eltare trl- other sYm-

bionts. Comnrensalism can involve other cnvironnlental nltvjitlca-tir.rns. The svnthcsi\ o1'acitlic rraste Irt'ltt'-': cluring lcrnlentrtiotlstinrulate the prolileratitrtt o1'llrore acid-ttliL-r.rnt illiar('\'l--iil,\lll\.rrhich arc onlr a lninor part of thc nlicrobiai ct,rntttiuniir xt Il.'.rtl'i.rl

pl{s. A scxrt! exarnple is the successitln c'rI nlicroorgitni.trl: ililringrnilk spxtilage. A: ittitrthcr exalnpie. rl hen biolllms trc lonrl:i t :ec-

tion lti.-1 ). the colonizrtiott of a neri ll' e.rpo:etl surilice br orre t} pe

ol nricroorganisnr (an initial coionizer) nlakL's it pilssiLrl.' tilr c'iher

nticrtnrganisnrs to attach to thc nlicrobiaill nloclitieri :uri-r.tce t'

Cornmensalisrtt alro is itllportant in the colorlization oi ti,ehun-ian bodl and the surfaces cll'other unirnal: and plant:. Thc rni-

crrxrrganisnts assoeialed riilh ltn anirtlal :Lin ani i'L'dr t'riilit'aan Ll\c rolatilc. strlublc. and panicr.rlatc t'rSlrltie ao:l)Ir()i-li'ld\ ii-()n1

rhe htrst as nutricnts I see sectitttt -11.1t. L'ntle r III()\l condilion\there nticrobes tlrt n(ri cattst-' hltrnl. othc'r thlin pos:ihlr contrihLtl-

in-r: to hrix11'uior. Sontclintcs $hcil the ho:t trrglni-':tl i::ire::crlor thc skin is punctured. these nornllllr ctrtt.tltlensli lnicroorgan-

isms nrar bcconie palhogcnic. These interactions riill be dis-

cussed in chapter 3 1.

1. How does commensalism d!ffer from cooperation?

2. Why is nitrification a good example of a commensalistic

process?

3. What is interspe(ies hydrogen transfer, and why can this be

beneficial to both the producer and consumer of hydrogen?

4. Why are commensalistic microorganisms important for hu-

mans? Where are these found in relation to the human body?

28.1 3 Microbial lnteractions

Predation

Predation is a u idespread phL-nomenon u here

gulfs or attacks the pre). as sht)* n in figure 28. I

(a\ Bdeilovibrio

(b\ Vampirococcus

(c) Daptobacter

Figure 28.13 Eramples of Predatory Bacteria Found in\ature. tal Bdcllovibrio. a peripla-srnic predator thlt pcnctrrit.rhc' ceil uall and grou's outside the plasma menrbrane. (bt li;r,;;,jp,i 1r1-1'11.s x ith its unique epibiotic nrtxle of attackinS l prcr lrr,i-

lcriunr. and (c) Duplobacler shou'ing its cytoplasmia ioeltlir,tt l:it rttlckr x su\ceptihlc bacteriunt.

lrrser or smaller ihan the predator. and this nomrallY re\ults in th.death of the pre).

An interesting arra)' of predatory bacteria are acti\ e itr trrtLtrc.

Sereral of the best exanrples are shoun in tigure 28.13. incltrd-ing Bdcllovibrio. Vutrt1tiroc'occus, and Duptobactcr: Eech of tlte :c''lt\ a unique mode of attack against a susceptible hactcrituir.Bdellovibrio penetrates the cell u'all and multiplies 'oelseen tlits'l- and the plasma membrane. a periplasmic ntode oi attack. fol-Irrrred b1'l1'sis of the pre,'- and release of progenr rsec.fi,r,urt'

l-1.-lJ This bacterium has an interesting life cycle. u hich is di:-cussed in section 22.4.

Nonl_, tic forms also are observed . Vampiroc'ttt'c it.s atlache:to the surface of the prey'(an epibiotic relationshipi artd thcn\ecretes enz\.mes to release the cell contents. Di;ptobacter

the prcdator en-

The prt-'r' e an be

t :,'.

:

@

Cl-.apier 28 Microorganism lnteractions and Microbial Ecology 28.1 4

The Many Faces of Predation

te 5i irr n

-'te ntion

.ri!'clion and

increased fitncss

The nricrobial loop. Soluble orgrni. nlriler tiont prirnrn pr()du.c,-\ i\ nLrnlirll) u'e.i br bacteria. $hich hcconre a prrticulale tirod siturce

for higher consumeF. Flagellates end ciliates prer rrn thr':c' h:r.lcri.r rrnil djr:rrt thrr':t. rrakin-c the nutrients they c()nl3in available again in

mineral form for use in primary production- crc-ating th!- nllgsqrir irrl l1r 'p. I'r tlii: rr :r r larle portion of the carbon fired b-v.' the

photosl.nthetic microbes is minerelized and rc'c}cletl (thu: tht tcrrr rriicrr,l.ill lot,pi rtnd d(^-s nr)t reach the higher trophic levels of the

ecos)'stem lsee figure )9.J r.

than *'ould rrccur if the predator \\ ere not a.ti\e.Bacteria retained s.ithin rhe predaror serve a useful purp()\c. ris in lltc trrl.iLrmriru(';', .ri toric h)drosen produced by ciliatcs in the rumen

toharmlessmethane.Also.trapping()fchloroplasts(klcptLrirlrrroirlr\l\ib\ prolo/,riiproridestheprc'clatorlvithphotosl'nthate.

The intracellular sun'ir.al of Legionelltt ingested hr ciliatcs pr()tccL\ it li,,i.-r :lr.\\d. \:.h as heating and chlorination. ln-gc'stion also results

in increase6 pathogenicit), when rhe prel is again rele rscd 11r tir. . \ l.in-:: ctt r r ronn::nl. and this ma1' bc required ftlr infection of human:.

Tbe predator sen'es a-s a resen'oir host.

Nanoplanktonmaybeingestedby'zotrplanktonandgro$ inthcl()Llil.rftL1.,udigcstire\\stem.Thc)'areth!'nrelcasedlotheenYironmentin r t'itter state. Dissemination to neu locations also rtccur..

ietrates a susceptible host and uses the c)'toplasmic con-

ts as a nutrient source.Ciliates are excellent examples of predators that engull their\. rnJ based on \\'ork $ ith fluorescenll) marked pre)' bacteria.'r-rle ciliatc can in-sest 60 to 70 Pre)' bacleria Per hourl Preda-

I on bactL-ria is important in the aquatic environment and in.irS!' trcltnrclrl \\here thc ciliates remo\.e suspEnded bacteria'. har c- ntrl sr'itled.

.{ :rirpririnS tlnding is that predation has man} bcnellcial c1-

l:. crpr'ciullr uhen one considers interactil'e population\ ()t'

.-i;.i'rrrr: unii prc\. as sumrnarized in table 2t1.3. Simplc ingc':-

r lnJ lr\\iiiliiation ol a pre) bacteriunr can lead to incrt-rt'trlr*r'l' n1111'1.'i11 clciing. critical tbr the iunctioninq ol'the rni-,hial ltxrp r tt't' st'ttirttt 29.1 urul figttrt' )9.1). In thi: prtrcc-".

.r.ri. ntriiir- produced through photos\nlhetic and chcnl$-

.hr; rr;lir ri\ is n)ineralized belore it reaches the hi!hcr corr-'i-.'ir. 3li1ru ing the mincrals to be made arailable to the Prillrrn.1ii,l;-.. in u "itxrp."' This is important in ircshu;rtcr. nlltriil.-.

r igrc.irilri .n\ ironrncnts. Inccslion 3nJ \hon-icrlll retL-nti\)11

'ir!.t.ri.r .i!.., are critical for ciliate functioning in the runlett-

lrr rnrthxnLrgcnic bacteria contribule to the health ol"Ihc ciii-. L'] decreasin-s toxic h)'dro-sen levels through usine H' to prt'-re .,]ethrne. \\hich then is passed tiom the rumen-

Pr.-ilation also can provide a protective- hieh-nutrie nt etlr ir.'i'l-

nt i()r panicLrlar pre)'. Ciliates ingest Lr',qirrnt'lltr and protc'ct thi:ronlnt paiholen from chlorine. uhich orien i\ u\eJ in an at-'tp'i t(r c()ntr()l lteit)nellu in cooling to\\'ers and air-conditioning

t:. L;c ciliatc sen.cs as a reservoir hr):1. 1,2'1j1t11a'1111 ltrit,it-,'rltrltr also lias been tbund to have a sreater potential to inrade

.r(rphr,!is and epithelial cells atier predation. indicating that

e.Iion not onlr provides protcction but also nlar nlakc the hac-

unr a betle. ,)uthogcn. A similar phenonlenon of surr ir al in pro-

rra has hccn rrbserred for !v'{vobacteriunt avirrrrr. a pltthogen ()f

rltlrridc conccrn. These protective aspo-cts oi pr.'dlltion harcjor intplications tbr survival and control o1'di:eatc--e uLtsipo p11-

,()rglnisnrs in the biofllrrl\ f rc\ent in rr rtr'r :rrpplies and air-

contlitroning s\ stenrs. In marine s)'stems the ingestion ofrllilr,,rplenktor.r bl zooplankton provides a nutrient-rich enYiron-

nr!-lrt thirt allo$ s nlnoplanktcrn reproduction in the digestil'e tract

Iili(i irl',\nlote \ dis.enrination in the enYironment. A sinlilar process

i ri;::i' llir-i bli;trnu rrc ing!'\lL-d b1 ptlll'chac'tes (segnlen!!-d

\\ r,: Ill\ li,ul'ti ttt, r.ll) ll) Il)lrnllC CnvirollmCnt: l.

I'r:;l'ii i,li..n sl',,,,,i intereslinr prc-riatorr skills. Sonle lunci can

ii.:i: i',:(1'.()1\r:i irr li-,r'u:r- rli rtiekr h1 phae or knobs. stickl n':t-r,. ' :i.. t,i lt', rhac. {)a i(\n\trii--ling r)r nonc()n\lrictinl rings. A cles-\ia e \.:ilniria t> .\,t:i;rttltrtins. \\'hich traPs nenlat()des b1 tlsL- ol'

.i,it:ii-ictinl l.ir;-1.. .-\ticr thc nematode is trappcd. hvphar' grou:t :, . . rrrir: ,"il;/-'J prcr und the clt0plarnr is used as a nlltricnl.( )ir.'; tirnSi hur t i..iriJia that. af ier incc'stion hv ltn un:urpc'cting

i1.ir\. ,jt.,\\i. :,itrj trii.r.jl, th.:.u'ceftiblg fiost I'rrrnt inside tlrc intcs-i;;r.ii iiit!i. i:, lit;. .;lulrii'ril Ih. Iun-gus p.'nclrliia\ thc htlrl ccllr ir-t

li. '::,Il-'1 :j iai:r-'.:\- ff(\a\\I iru. pre tliriir.i:. u hie h u.uiill)' has a l'atal and tjnal outconle

i,'; ,:r in.1ir;!irilrl i.i.\ (,r-!rni.nl.hasauitlcrangcof henct-icilrl cl'-' '. ,:, ,' .'r,\ir\. lrn.: r. critie:rl ln thi l'utltti()tlin'j ()l n;rl-!,._ :'

tii:!l en\ irir;lrtlitli..

Pa rasitis m

I'arasiti-snr !s onr ol'thr rlrost eLlntple\ nricrobial interaclions: the

lin.' h.'rri r-cn pararitisrn and predation is difficult to def rne tlig-Lrr. l:i,1. 'ti ,r/.r,, .\('(ti()n -iJ. lr. l'his is u relationship in rihich()nu rrl'ri irilir bdlr.flts tiont thc othcr. and the host is usuallY

hrr-nrr:ti. l-hi. rrin ir.:r,rlr c nutrient acquisition and,/or phr:icalnririn!alllnlc in or on tlie- hosl. ln parasitism there is a degree olci'e r.isicnie r)1'th. p.lrasite in a:sociation ,'r'ith the host. Depend-

ilrl on the ctlrriiihrir-inr betueen thc tuo organisms. this ma1' :hiftanrl ri Irrt rrriSht hlir c becn a \tablc parasitic relationship ntav then

bccoilr.' r prth()sL-nic one \\'hich can be dellned as predation.

Sonre bactcriul r iruscs can cstablish a lt'sogenic relationshipu ith thcir h()st\. lind thc viruses. in their prophage state. can con-

fer positivc ne\\'rtrributes on lhe host bacteria, as occurs \\'ith

Microbial lnteractions 59128.15

Figure 28.14 l-ichens. Crustose (encrusting) lrcherlt gro\\ rns

{,11 ir ! l:!nili Po:t-

:,r\iJr 1rr!,!lilation hr Crrnrrellocleritutt tliphtltcriut (\"t \"(Irr)/r\

,'-.-i ,,,,,,' -i+--i t. itai-eriiic fungi include Rhi-oplttdiurtt spltttttti-

.ir.,ri.r,r. .,', rllt rhe llLl .!;,.r'rp1,.' 1i. ,\l:'.'. Rlri:.octt;ttirt sr'/itrri i' lt

a,,,,.,,.',. r,i' l/:tt lt-llllti P.r'I/titirrl' u hich i: itllport:rnt in triocontrol

1rr,ra"rt"r. iiir- tt'i' rrj li;11- 111i611 'rrr!lLIlislll ltl Crrntrol an()thct- Hr'l-

,;t,,ii .::..-..:' -iiil.ari irq i i111sgr. nlicletia. l'ungi. i1nd pr()t();/()lt ltr'

l-iehens irle til. :-l:\(t.iJtion {L*l\\cen r1e-cilic a''eolll\ccte: (ih!'

l.:n-!:ii. .:i,!j .lil-1lliir rana:-li oi- 'lihci !:rL-'n algiie ()r L\ itnrlbitctcriit'

i,t,, li.i",'.111r lu:lSr'i irlll1 ncr i\ l'rllleJ the nllcribiont und tlle li-

-:..r1 i'r -\iril,'a,li.tirilil f:11111cr- rht- phlcobiont' [-icht-'ns i]rL'illl c\-

..iic,,t;r.,r,1lie t''t ii c()rllrolied parlt:itisnr ttigure 2ti'lJl ln thc

ir:!\tti)cliilicn.rnltrio\i\\\'as(jollsideredttlbeanlutualisticinler-,,-li,,l. ir iirLtn,rl\ he. i'ccrr lil,rnJ thlrr lr lichen \\ ill i()rlll t'lilr shcn

',ltr iiio Ir\riarlljlti fr:il-rllcir ',13 nr;1fi1iottltlli dcprired Untlcr tltlrtltll

-,,;,,liiti,t't. lllc l)t)tanlilrl f.lnncr' :'1rcll't interl-sted in each uherl-fltl rcrllarkllhlc illpe.l ()l lhi) ll::ociatii)n is that it: ttlor-

'r1,,11,,1.. i.iit.1 tllatilt'()lii i"e iatit'il'hif \ are so c()nstant that lichcn'

.,:. tr..i:rtr'J 'lallil'la iirrrl 'Pccir'' Il:tlllc\' 'l-hc chl'rlrclr--rirtit tll"r-

:r,,,i.,1r ,,1 " lit,:rl liche rl is x !l()pert\ tlf the asstlciatitln and is

:r'.r .'rhihireLl br citilc; srtrllionl irldiridtralll''\'::

ilte aute rhe phr coiriont i\ a ph()tL)autotroph--depcndent onlr

,,r lirht. earhorl tliori,lt- lrnd cenain nlinerll ntltrients-the l'un-

-,.,r J,,,, qct it\ ()rqunic e lrb()n directlr ironl the aiga or cr.anobac-

1., i,,,,r. Tlrt lLrtlgus olte n ttblirins llutrients frorn its panne r b\

hlrurtor-ia lf roicctions o1' l-unqrl hvphae) that penetrate the phl -

Cr\tir.ri.tI ccli rrull. lt iil\o Llsc\ thc o. ploclscer.l dtrring pfi1'cobi6nt

Irl-i,)ir)lth()\iittr;t llitigtt itt e .trtr itr! ,rttt I'Cipirlllir)ll. In turn the ful-

rr.t\ prolccl\ tIc pltr cLriri(.)ttt l'l'prlr high light iltensitits. prgyi'-1es

r,. .::r-f lllttl ,,'rincrals 1., it. lilt(i cielltts ll t'irtll strhslr'atutrl $ ithitl

\\ :'rJh thc i.it) c0hiotll ciill qr()\\ Pr()tcctcti frrlitt c-nr irtlnnlentel

\itj>\. -f he -,i.ilin' ot-thc tirtlsLt: to pal'asitizc' thc' alga or cvanobJC-

t.;-iulil undir \Llch lonscr-tcl't'll ctlrtditiotls alst'r has bec'n tlescribed

ii: .r li)rIIl r,i ir-rlt gal -,.i i rL-ctccl "ili gliclr I{ trre "'.\tr irttp.,rtlitlt rsJ'eit o1'I)lil'ilsitisll'l is that tlr't-r tinle' the para-

.il;'. trttce it hls cstahlishc-il a relatiorlship r'r'ith the host' \\'ill tend

to .1i:cat'tl e \ccss. tilttt:cil gcllolllic inftlrtllatitln' I process of nras-

:ii: g,:ntltnic reductioll. Thi: ha: occttrretl * ith lfr't'rrlrzrt'teriirttr

7.-,,,i;f i.rr, -'r. -iJJ ). lintl u itlt tltc rtlict-o:Poridiuni En<eph'ilito-

. i,, ,, ,,,,,i,:r/i. Tht- Iritte r tlrgaltislll' \\ hi'h llarasitizes a rr ide

rlit.,re o1'anintals. irtclLr.lirtg hltlltlttls. Il(r\\ cltll olilr surrile in:ide

tl'rc host cell.

1 . Define predation and parasitism. How are these similar and dif-

ferent?

2. How can a predator confer positive benefits on its prey? Think

of the responses of indivicl'lal organisms versus populations as

you consider this question.

:. What are examples of parasites that are important in mioobiology?

4 \ /hat is a lichen? Discuss the benefits the phycobiont and my-

cobionl Provide €3r,1 oth€r.

Ar-nensalism

-\nrensalisnr rti()rir rit; Lrrtin ti.l-ri1r: iil lha rltllc table) descriL'cs

ih-- :lrlrcr.< ai'lcct til:ti \rll!'ttr-l-iTli\rrr lr;'' 1';1 1f i1[gr organisrn as

.i],'',rlrirttl,:nl'elS.1 T|1i'i:rLirliiiir..iir"rlll prtrcesshasedonthe

r.ill;t.r'oi:i.nr:ci1-lc!,1:llnrr-lll(i hr "lc''l'lJili\ll-1 lrhichhasaneg-

il'::i j ailr'Ji ,r1 ;i11,rii'i';1 \)i!lil:i'll-i' '\ '':r"t- lrl:niple cll'atnen>al-

i';:l :r tll'- i:i\r!itl!i)rlll i-ri ;1;1',if!.'ii" iill': 'itll

int'tit'it or kil! a

\'ii.rcirtibl. :itict-oirrg-iilisllr iligurt lti'I5a i''l'he ettine ant-tunsal

11 r i, xl 1.tic rcllititrtl.ili i-r i \ ni irill{ !icL: h" rinl ihiotic-pro'lucing h:rc-

ii:'r, lhlii .:c lllltlili.rii-'cci iil iir': iL::l:li1 glLl-ticll \)'t(-nj tfigurc

l:.151, l. In this cli-c ri \tl .l)i\)lll\lclc lrirlJilce\ an rntibiotic thlrt

ait"tr(ll\ E\, .)1 /'1).\1\, ll Pcl \i't'nt lriii'l']LIs ILln!us that can destrtlv

th. i.illl's tirrrgal gartitn. Thir r,rniqu.- ;.iltlcnsalistic process apPe&rs

tr, iri\c c',,,.-iied 50 nliiiioll \ri-ll': l.-\) ill South Anlerica'

Other i ntpOrtltitt elilttt:lLl i :tic rt ilititln:liip: involve rnicrobial

pr,rjr-tctiirn 'r'l' :Pr-cillc i)rclttlic cottlptlunds lhxt disruPt cell uall

,,. i..irrrrr,r liicniL-.renc integ|itr. 'l'htsc irlcIudr' the bacteriocins

1,..,tr|,- l9l. 6,\5t. Bactcriocitir llrL'of incrcx\inq interest as l-tlod

:r.:.tiiir c: ir,r contK,liins rrir$ rit rrl u: lc.ircti plltholens (sst' st't'-

'tir,r -i I .-l t. .\ntiLracre,'iri1 p.-1-,tide s Al\() call bc re lcased b1' the host

i'', thc irtte.iinc atld olhcr placc': The -' tnolecules' callc'd ce-

ci{ririns in insccts and tlefcnsirls in nlatllnllls' recentl}'have been

,c.,,g,,i..-J as ef 1'cctor nlolccules that plar ;gniflcant roles in in-

rii!i. inrrunit)' (.scr'2. 697). ht anitllals thL-se lllolecules are re-

ler.ecl b) pha-uoc!te. ancl illtc:tinal cclls' ancl 'rre as Po\\'ertul as

tr-t:lict'clinr':. ILeccntlr it has bcen lound that hrtnlun \\\eat is an-

tiilticrobi]1. The srrear glund pr,rtlLre.: ull lLntin-ricrobial peptide

592 Chapter 28 Microorganism lnteractions and Microbial Ecology 28.1 6

1

arn I

C!ltivatesfungal garden

Parasile oniunEal ga:der

Figure 28.15 Amensalism: An Adverse ]licrobe-\licrotreInternction. (a r .-\ntihiotic produclion and inhibition ol grouth\)i:tr:us!iptlitle br;1,.it,,tl on:rll agar ri-iediurn. tbt-\ schematic di-

agr.irr describi n-q thc rrse oi antibiotic-qr,"Jucin g streptomr celes blant\ tr) contr()l ilngal parrsite-. in th.-ir 1:.rncal sarden.

thui has been calie.i dcrnricidin. It hr: been suqsc.'ctL'd that thc

eri,ilrticrn ol lhc \\\tat gllind trtar tt i-:iutr-d io the abilitl io pro-

due e this conrpolu'rii and rnhibit rnicrt.'t'ial inf-ection in this sensi-

tir c area oi lhc L'i-d). Th.- skin also pi,'duces similar compounds:

r reientlr ri::gt,\ c:-r-tl llrtiiiitiJrt)cii.ri i]-'l:iaie ha: heen called cathe-

irciiiin. Finaiir. tirctrir.,ii; irr()di.lui\..u.h r: orsanic acids firrmed

in icrnrc-ntr.iti()n. can prltduae altlcn.-rlistic et'i€cts. These com-

l{)unds inhrhii gri.ri ih hr chlnginL lt. L-nvircinnlenlal pH. lor er-anrpic. tlrrrinS trrtliril ntiiL :poillSe \',. i :e cli()tt 11.2).

Competition

C--ompetition arisc: u hcn differ-.it n'iicrrror-ganisms u ithin a pop-

r-rlrtion or conttt'tLtlrit) lr\ t() r.qLrire lhe rante resource. u hether

titi: i: a phl:ical l,-)ulrti()ri or ll partictilsr limiting nutrienl (t-rgure

l"\-i ). If one of thc {uo c()tl1pL-ting i'rrrni\nl\ can dominate the

cnr ironrricnt. r*. hethcr br occupving the ph1'sical habitat or bv er-clu:irelv u.ins a iinriting nutrien' ii 1\ill outsro\\'the other or-,jani\nr. Thi: phtn,rrncltt)n \\as stuii.'J b1 E. F. Gause. uho inl9-r-t descrihcti it as thc- competitir- exclusion principle- He

ti-rund that i1-the t\\(r c()nlPeting ciltates overlapped too much in

tcrnrs o1'their resourcc usc. one of the t.'r ' protozoan populations\\ ir\ excluded. In chcntostltts (.r('.' se L:Ii()tl 6.J). ue maY see conl-pctition for a lirniting nlttrient xntonS nlicrt'urgenisms u'ith trans-

pon svste m\ ot'dit'lering aftlnitl . Thi: can Iead to the exclusionof the slorvcr-grc-rrr ips lltlpLrlation under a panicular set of condi-

Antibiotic controls {parasite I

^@l

tions. If thc' diiution i.,ir' ir changed. iitr' prc-r'ilttrl\ \io\\'er-tro*'ing poPuiitii()n nlr\ haii)nra' cklntit::r:rl. Ollr'n t''r() rttict-,rbial

popuiation: thri llpperr lo i.rc' 1iv.l1ii;pr ncr cnhtlr-r: a(ie \i\1. Jn thisCa\e. Ihe\ shlre thc lin,:::.r,-, l.-..,Urr.L' r \l:r\.i,. :t iinr:tirtr nr:t:-tenl )

and ccrexist shilc surri'.,:: ll i..\\er []!]it'rllilt:i,n llr.-i..

1. What is the origin 0i ire tern: amensaiism?

2. lYhat are bacteriociirs ?

3. What is the tompetl:i',* exciusion principie?

Symbioses in Cornplex Systems

It should be ernphasiz.'ti iirai tirc :y rnbi'rti; nttcructiott: dt:;r-i.setlin this section Li() r'r()t ()a-Llr itt.lci-.'lr.i.'nlir. Each rinrc u riti;i-r.,or-

ganism interaci: $ itlt 0ti.'r orjirni\ln\ lnd the ir en\ ir()tiltl.iri\. ir

seriesclf t'eedba;k rcs;rt,rt..'\ ()q!Lil-\ irl ttrc largertrirrtic L{)llltrlLltlil\that $ ill itnpa;i other i.lri1: qtl ;';irrt \le Ill\. .\\ atl illu:tratir,ll. thc

interacticrns het*c-en thc nttnrlr'.ic l',Ltitrt.:tt'itltu.s /).i/1r!r1ili'r,(\ alrd

its cooperative :ulflde -r,riclizin.: hae lc'riLrrtt (p. -ili: t ittr olr c\ u \c-ries of svmbioric interl.-tions. as shogn in figure 2t1.16. In thiscase. the cooperative inieraclit,rt l.etr.rcen the ttentatode\ rr-rli tllcsultlde-oxidizing epibiont is int.iuencc'd b) thL' population sizc o1'

the asstrciated brcteriurll. ancl rr h,:thcr il i,. host-ltssociatcd or lrcr'-liring. This equiiibriurr benr.-cn host-as:oeiatr'd and f rc'c-iir ing

bacteria is cont:-,rllecl h,r a serie' o1' t'eedback pr()ce\scs thet in-

(b)

Streptomyces L€L;cocccrini in fungai garden

)Q 17

Nutrieais

Free-livir: !acteria interacling \T ithcompetrra bacteea for nutrients;

both bactena are grazed by the predator

Nematode andhost-associated

bactena

Figure 28.16 Conrplex Itrttrat'tions irl \licrohial [-colog-r.

Interlctions hctgr-.'tl the nllll-iill If i::;11\rr:. [":ri't':lt'iL i::rs lt'tt''t-.sili['rrr.s and ils host-Li:sttailitc't] -lll.1 ii"!--]r\ ;": e'rtrilcr:riir c hltc-

teriu arc inlltrenced h1 lc'rr'l' i'l ttlrilir'itt'. -,' ritll lt' hr olltcr

bxclerir coniPeting 1-or thesc ntttl'1.llit. Pt cti:ri,':'- in lttirl. u\c hoth

lhr' li.-u'-living c()()ncruti\ c l.:r.1riiri i.r.i ill. -.'rllirail)lJ ..r.tariil a\

lipd stturces. lcadilrg tti colilf lcr 1c'c,lh;ick :"!-\ll()ll\L)\ :l lhi: d1-

n:lfilic cco\\ \tcnt. --\rr(l\\ r sltrr,,i irr'tlai i.ilil,,: anhillla j:l : itttcruc-

tions: lines uitll :llllLll cil-ill' l:,.1i-eia ;r'':':llrt'r: .1;""'ri'1'

i ntcractions.

y6lrc crrtrlpctititrn lirr srrll-i.1': '.\ i':;l ()iilJ:'i'11.1u4..,. ltliii i)rr.llttl()!l ()il

the cpibiont alld ()ll Iilc cotilirtilll: l.:":''l l"' -i':ll:' lhc e :illlihriLirlob\ened at all\ tirlle i: the ic'irlt ()i -1 \eiia\ rrl ttllrr.i--"irrll\' il'l-

volving cooPeration. Predatii )n- and ctriltPctiti"n.

fzca NUTRIENT CYCLING INTERACTIONS\c7l\Iicr(x)rSartisllt\. ilt lhC c()Llr\c ()1 iilair ir\)\\ til lttlti lllctlrlt,rii:lll. itl-

terlct\\ithcuch()thJI inthcc\(lirl'iL'l:,.,iti''il'r'.ittilii.il;r':eltrt"rrl.sulfur. nilrogcn. pho:phtrrtl\. ll-trtl. -r; . Ill-lll,-ril!'sc.'l'h:' tltltritnt

clcling. caller-l biogeochemical c\cling.1 11t'11 ;llpllc!l',\) thc cn\l-rontrent. involr cs btrth biologiultl an.l .ite ttli.lrl pro.c'-ir- Nutri-

ents arrL- tlrpsli)r1tl-d llld c\ clcd. (Ji':.n tr) t'ridlitit,n-rctlLtction

reactions (st't' .tt'tlitttt,\.-i) that cllll e h:i;lrt tlle e hcrllical antl phr s-

ical character-istic: 91'the nutrie tlt:. .\11 ol thc bi'rscochlnliclrl c) -

cles arc linkcd tligure 18.17). .Li-,.1 tllc rrlctxb(tli'rli-relat.dtranstirrntatiotrs ot'!hcse nutricnts hltr .' llitbltl lcr cl ittlplrcts.

Nutrient Cycling lnteractions 593

The rnajor red:cr'd and oxitlized fbrtlrs of ,1',.' 111trst illlPortitlltclcnrcnts rrrC n(rtr-J in table 28,"1, togcthr'r \\'ith their r.alencc

:tltcs. Sicnil'ican: gtist'tttt\ t(rlllp()l1L'llt\ tleettt itl 1lt.: cerhtltl lttcl

niinrgcll a\clcs ar-..1. to lt lesser cxtcnt. irl thc sr-rll'trl-dvclcs. Thr-ls

a rorl. aqr-rlttic. r)a inllrirte ttticrttorgltttislll ofie n cxll f i\ gil\c()Lls

lirr-nrs ol' crrbon ::rd nitroge tt ct'rttt1-rottnrls. Irt tltc "sctlilll!'ntar\ '

CrCleS. SLrCh its th,,t tbr iron. thc.rc. is Ito gasCous CL)lIlt()nL.r)t.

Carbon Cycie

Carbon crln bc prr-.eut in rcdr-rced lilrtl'ts. sr-rclt ils lllcthalle {CHi)and orgtrnic nrlltte:. ar,tl in tttttre oxidizcti 1,,rtlts. srtch ll\ cilrb()ll

nrono\ide tCO) a:''J cariron dioxide (CO.l. 'fhe ittliot pool: pr''s-

cnt in an intc'_srat...t basic curbon crcle ar.' shos tt ttt I'igure 2ti.1ti.

Elcctron don()rs te.g.. hvilroge n. r" hich is l strong rr'duclatlt ) atld

accL'ptors te.g.. O,, inilr.re nc.- the course oi bioltlsiclLi atitl chctll-

ical reactions inr.:iling carbtttt. H1'drogen clttl be prodltced Lltlr-

in g organic niai::r dcgrltdation espe cialll untlcr attaertrhic

conditions uhen I:rnrentation occurs. If h1 clrtlgen and rrtethane

arr' generated. the\ can mo\'e uplvard frtltrl anaerobic to aerobic

areas. This creat.s an opportunitl' tbr aerobic h1 dlo-ren and

nrethanc trridizer- to funetir'tl.l\{ethan.'ler.e,: in the atnlosllhcrc hare lret'n irlcteltins xp-

proxinratelr' lii itr lear. 1'ronr 0.7 to 1.6 r'ir I r pprlr (r'olr-rtllet irl

rhc llst -i00 rear.- This Irlctliane i: dr-rirc.l fr,rlll ir \rtilL-,. ('l

\()LlrCCS. lian atl,'itiC \\'iitar colur1,)r', ia 1[ro\e the anlrr'rrrbic ztrnc

u hcre the nrcthrll,rscns are located. the nle tilant- curr be .rritiizcdbclorc it reaches :;.tc atrnosphere. In tnlnr situalttlns. such n: itlrice paddies li iir.rut att overl-\'ilM aertll.ic \\'i1ter zollL-. thc

nrcihane r|ill hc icleased directll ttl thL' atlllo\ph:rt. tiltts ctrtl-

trihLrting to global rtnlosPh!'ric lllethilne itlcrerl:es. Rice nrLrlJies.

rurninant:. coal r:inr-s. se\\ rtge trcaltrent 1llants. iarldlill'. lndntitr\hL-s are imFliiant s()tlrce s ol trlt-'lltattc. .-\tllter, 'f it ttli.rt'"1-ci.lnisrit\ iuch ar .\!11 1a1111,1,11'l iltrit tr'r in thl cLti. oi lti ttiiie . .,1>rr

aJn c()ntributc t() :llatltilnc ilr()ducti\)i). :

::.: .r:..i :itillri::ti iri - --. ii\i). i \\ \tr. ---" '

Carbrrn llrlti,'r occurr Ihttrugh thc uctlr itie r ol cllL:ltrb:rcl.--

rirr atttl trecn alS":. pltolo'tIlthetic bactt-lilt tc.c. i/rir'tii(iii:tt)l::ttLl C I t ! t t rolt illrr r. i:rld lerobic che Ittol i thrxLtll\)tr()ph \.

ln thc carbon ircle depicted in figure lS.i8. no distineti,rn is

nrade betueen dilierent tlpes ot'tlrgattic lllatter that are lorilledlunii degraded. Tn:. is a tttarkc'd trr er:ililplif iclltiotl Lre'cliu'e trr-

ganic rnatler 111i3- s idcll in ph-r sical cllaract.'ri-tic: iitld i:l thr'

hitrchemistr) oi ii: s-r nthesis and de-cradation. Ur.'Llitlic ni:rttcr

rlrics in ternts oi elcnrtlttal cotttposititrn. \trllcturc oi'hli'il re-

fic.iling units. linit::ges hctu c-ctt rcpcatills rtilits. and ph\ \icili lndehcrnical charuetgri itics.

The tbrrnatioi o1'orgattic tltattcr ir dise Lrs:cd irl elllipter-. 1()

through ll. Thc d:qraciation tlt'this organic illltttdr. ot.tcc iorlllctl.is inlluenced bt :' serics ()l-factors. TIlcsc incirrdc (l) rttttrients

prcsent in the enr irontttct.tt: (l)abi()tic conditions ipl-1. oridltion-rc'tluction potcnli:'i. O-. osrttotic conditions). and (itthe nlicro-

bill communitr prescnt.The nrajor cL.3tplL'\ organic substrates Lrsed br nticrtrorgan-

isrns are \unrma.zcd in table 28.5. Oi lhese. onlr.' []rL-\'iou\l\'

/

-t

28.1 8594 Chapter 28 Microorganism lnteractions and Microbial Ecology

Beduced forms Oxidized forms

Lrght

LI;::

Figure 28-17 trIacrotriogeochenristr-r': A Cosrnic Yieu'of \lineral Cy'cline in \Iicroorganisms. Iligher Organisms. and tlrc.\bioticChemical\1orld. All hiogr'ochclni.rl e\cl.--:ri-. linkcJ.''i:rhc'nr'r:-r L,einsobtainedfromlighrarxJprirrolreducedandrr-.:-

\\OM

1"1i.1'

!irr\\ n rnicrobial bi(lntass contain\ all ol'the nutriL.nts reqr-rirc.d tirrrlicnrhial sro\\'th. Chitin. prolein. micnrhial bion).lss. anti nucleiceci-ir contain nitrogen in liirge atn()u11l\. Ii'tltr..e \ub\tir'Lc\ trr.e

Lr.i:ti lirr cro\\'1h. thc'crcess nitr()gcn lnrl othr'r nlineral: Ihat arL-

n(r'l uscd in the firrmation oi ne* nricroirilil birrilass uili be rc-lca.ctl to thc- cnvironntcrlt. in the pr(rce\\ o1'rnineralization. Thisir ihc- procerr in rvhich organic nttttL-i'is tlccornfrosctl ti, rL-lelr:e

'ir;i.le r. inorganic colnpoLrndr {c.g.. CO-. \t-{- . CH,. H- r.

Thc other cornplcr substrates in tibic lS._.i .'t)a,r1,, onlr clLr-hon. hvdrriSen. and ()\\'_ge n. Ii nticroorSanisrtts r,iiL' [(] qr()\\ b\ Ll\-ing thc-sc- substrate\. thev ntust ucilLrirr. tht'rentlrining nutrientrthcr ngscl ior biomass s\,nIhc\is lrrrnt thc e nr ironntent in thc

nr{,.c\\ of immohilization.The oxr gen relationships lirr the u.c ol'tite:e substrates also

ilrL- (rf interest- because ntost of thcnt can be desraded earilr r,, ithor rr ithout o\\'sen present. The erceptions are hrdrocarbons and

lrqnin. Llrdrocarbons are unique in thar rriicrobial degratiiri...'.pecirilll of -straight-chainc-d and branched fbrnts. involrc. rhcii,rtill rilditi.n of nrolecular o.. Recentl-r. anac-robic degrriJati..ol hrdrocarlrons \\'ith sulfate or nitrate as c-leclrt n accepl(ri.\ hlisbeen ohrcrled. With sulfate present. orsanisrns of thc ScnusDtsul.li,t'ibrir) are active. This occurs onl-r .loulr ancl rl.irh nri_urohiai c0lnrnunities thet have been expos.'ti to thcse cornpL)uri(l\lirr -.,.nU.U periods.

Li-tniir. tn inrponant structural componcnt in nrature plant nra_tcrial:. ,. a cornplex antorphous polvmer based on a phenvlpropanehuildinq block. linked bv carbon-carbon and carbon-c-rher boncis. Irnrakes up..pproximatell' l/3 of the r,,,ei_rht ol.u.rxxl. This is a spe_cial casc- in *hich biodeeradabilir'is depen<lcnt on o. a'aiiahiliti'.i'here .ften is no signiticant degradation because nlo\r filarrentousl'unsi that degrade nati\.e lignin in situ can function onlv under aer_obic condirions: oxidases can act bj, the release of active o\\ sen

co2. No3-, so"2-, Fe3*, l',lnrv,

------

/

ol,4

28.19 Nutrient Cycling lnteractions 595

Forms of Carbon, Nitrogen, Sulfur, and lron lmportant in Biogeochemical

.llajor Forms and Ialenccs

Cr cleSignificant GaseousComponent Present? Reduced F'orms Internredi:rte Oridation State Forms Oxidized Forrns

N

.rts

NtrFe

Yes

\ts

CH.( --1)

NHr-- organic \(--l)

H1S. SH rroup'in o1:enic nratici

{-2 )

Fer-(+2)

CO(+l)

(t)

S'

t{} r

\,or+l)

s-o,li-l)

No,{+Ji

so.:(+-1)

CO:(+-+ )

No,(+5 )

So.'(+6)

re(+l )

se{i{ffiGr}. nuEietrl c}cle- Major red*ed- imermediat oxidatio sl& aod oxidized fms re !d.l- tosethcr $ ilh \ alck*.:.

\pL'-1e5. t-ignin's lack of biodegradabiiitl under atlac'roLric conJ!-

tion: rc .rlts in accutnulation of lignitied malerials. includin-g thc

lormation of peat bogs and mlrck soils. This absence of lignin

dcsradltio" under anaerobic conditions also is inrponant in c,rn-

struclion. Large masonl' structures olien are built on \\\ 3mf \ \itc'\

b1 dnring in "ood pilin,ls belou thc \\'ater table and placing the

bLriliiing tootings on the pilings. As long as the tbundatrons rL'nlain

\\ater-saturated and anaerobic. the structure is stable. Ii the riater

Aerobic

Carbon'fixat,ca

lrririr'rir.,rl.r:. hr,i,.tit-r. thu- piiings uill bc-gin Io rot and thc stntcturc'.,. ili hc ihrcutc'ntd. Sinrilurll. the clcenup of harbors can lead to dc-.'l)i11ir()\ili()r1 trf costlr drrcks built uith uooden pilings due to in-e rea:cd ticgratlation ()f \\(-\-ld bv aerobic tilamentous 1ungi.

Thc' pr€scnce or abscncc of o\\'!:en also affects the final prod-

Ll.t\ lhJt accurrulate \\ hcn orgrnic substrates have been processeal

hr nricroorlanisms and rnineralized either under aerobic or iinaer-obic conclitions. Under ae robic conditions. oxidized products such

Anaerobic

Carbon fixationftr"","..ffico.

rlrini.rride (

obic pr()cesses are noted \\ ithcu..rd in clrapter 19.

co.

A& :""H1."& oxiCalion

CO

hlue arrous. and anaerobic ltr(\cc-\\.\:ir::h(r,,\rr uith rt,l afrfr\\\. Rercrsc lllcthallogenesiS \\ill be dis-

(cH.o)

cH.

rbon Clcle in the Enr.ironnrent. C:rrbon firutit,n.irn occur ihrough the activities of photoauturophicganisms. Ir,tethane can be produc.-d t-ronr inor.::inic \r,rt,.trxt.s lCO- : H.)r,r iront orsenic metter. Carbort

sources such .ri automrrbiles anJ intlLr.tr'. -i\ i-r-trrr'r)c!l trr litc carhon cvcle hr CL)-oxidizinc bacteria. Aer-

\.--Jr-'" \\e\*

Methanogenesis Methan€ oxidairl.

Figure 28.18 The

Anaerobic respirationand

termentation

'Sg" Ci'acter 2E Microorganism lnteractions ancj Microbial Ecology

Aerobic c.:-5on use

Chemoheterotrophs

Anaerobic carbon use

Oxidation ofreduced products+H.O

+NO.-+NO,-

> so'-

Chemoautotrophs

Organicfernrenlationproducts

Ca.can use[,iln mineralrei ease

28.20

as nitr;.rtL'. sull'rrtc. ar)(l .rrrbon dioride (figure 28.19) $ ill resultl.nrnr rlicrobitrl (lL-gradiition ot-crrrnplex (rrsunic nlltter. In ctrn.r-

palist,n. Lrrrclcr unucrobic condilions rcrlLrced end products tcncl ttrluccunrulltc. irrcltrding.rnrnronjurn iirn. rulllilt-. ltncl rlc.thlrn.,.

Ti-tc'se oriilizccl an.l rctlr.rce.l tilrnts. ii thev rr.ntrrin in Ih.- aer-obic r.r lnacr{riric en\ iionntcnis ri hcre ther n'ere tirrrnc'd. rr illrrsrrallr ()nl\ \er\ e lis nLrtricnt:. li nriring ()ccLlrs. ori.lizetl spccie\I)tigltl br- t.ttor ed to a nt()rc rcrlLt;.'.1 loltL'or rctlucer-i sltecics nrirlhtbc nlt,r r'tl to lL rttore orirlizcti .t.rrte . Llndcr sr-rch circun'rst:.tttccs.additir.nal L-nL-rsetic pr-.'i [ri I iti;: ( ] inki ng o1' clcctron irc.ept()r\and (l()n()rs) $ iii bc crctitcri. lr-tiJilt! to successilrn and i-rrlher nu-tricrtt cvcling lis the>u- rnir.-ti .,tidants irnd retlLrctants lifl. L.\-

nloitt.i l.r tlt.' rtri. ri'lri::l .r,nt1t...:rilr.

1 . What is biogeochemical cycr ng?

2. lVhich organic polymers discrssed in this section do and do notcontain nitrogen?

3. Define mineralization and imrnobilization and give examples.4. What is unique about lignin and rts degradation?5. What C, N, and S forms will accumulate after anaerobic degra-

dation of organic matter?

>irrf.f -ytie\lrcrr.()icani.nt\ c()ntrinr-rt. qi-::il\ to thr :uilLrr r-\ iic.. lr sintpli-lled r ersiort rrf u Itich i.' rhi,r,. n ,n tigure lli.20. Sullldc can \erleas an .'lL'CtrOll 5()tlrce ftrr both ph.rtOsl nthr'tic tttiirtrrrr!anisnt. andchenri.rlithoautotrophs \Lrih a\ Ti;.ittbiitiliLts t\LL,pl). lS9-9() utttlJt-l ,t-; r: it i\ coltvcned tri elei:tc'ntlLl suliur lnd rultatc. \\-hen

H

NH.Complexorganic matter

Complexorganic maiter

H.S

CO

HS

CO,

H.

cH.

',.3 r, OU S

c r emo h et erc't ro ph s

Methanogenicsubstrate producersand methanogens

Figure 28.19 -l-hc Int'luence of O\) gen on Organic llatterI)reonrpositiort. \1i.r()orsani5ttts lbrnt difl'erent prodl, 'ls '\ l'ir-rL.:-tlri.rlrL rl1, ,i ;r .i)nit.i.r rrrsenic nratter aerurbicall\ than thev dcr

r:::.1.'r rrir:,;: ;':. r r'ir;i,.irlt:. L'ndc'r eerrtbic c()nditions oriclizcti1:1, r.1111ir ir. ...::rriilie . .'r irilc r.'JLrccd products ltcctrrrtulate iutlcr()-i.,,l,lij.-[-ir;.;'1'.qglirr;t..rl\r)i]lirstratc-c()nlnienvll\tictranslirrrna-1;,,;;. ol ri ..ri..ii':rla. ',i ircrt thc \\'ilslL- Pr()duct\ of one grorrp ol-

l|iui(r(rrrltnr.rrr. iln i.t urcd hr a second t)'pc ()1'lt'ticIt','rIlr|trstI.

Carbcn use

Complrx nic Substrate Characteristics That lnfluence Decom on and Degradability

[,lt'menlt l'rtttnt in ltrlt {)uuntitt

\ul).trr(c Ilaric Suhunil l-inLagts (if Criticalt C

[)tgradation

\oH \\'ith (). \1 ithout O,

Surch

Celluiose

Hsmicellulos.'

l-ig ni n

Chitin

Prr )tei n

H\ dfi)c[h()nLipids

Ilicnrbial biomass

\ucleic acids

Clucose

Glucose

C6 and C5 mono;a!-charides

Phenl lprupane

-\'-acen lclucosamine

.{mino acids

'At iptraric. c1'clic. anrmatic

Cllcerol- fattl acids:some contain phosphateand nirrogen

Purine and pvrimidine bases.sugars. phosphate

G( l+ -1)

c(( 1r 6)

ptl+-lrpri+-1i.pt i-.rr.

pr l- or

C{. C{) honJ.

Br l+ lrPtptidc htrn.ir

Estc'rr

Vaded

Phorphrilicster and,\ -slycosidic bonds

+

+

+

+

+

+

+

++

++++++++++

++++++++++

+-+'+++

NH..

+++-

+

+

+

+

-t

za.z r

Desulfovibrio

Organic sul{ur Sulfate Elemental S

reductionidissimilalory)

i",1r neral ization

'ultat!' ditlu\e: inir.r reduced habitats. it providr's rn {)pl\rnunil\lrrr,l:ar'-itrcltt qr '-:I^ of nticr0or,f;rlli.l1l\ [r] -ilrI\ (rUt Sulfate fe-tluction. |ro1 gr"'ttplt. $ hetr a u>rlrit orqlltiJ cl!'atitrn dtlnt)r i'lrrc\uiil. Dt'.sttlfl ,i ili-ir) u\es :lrlflitc as lLn o\idrili i \( t ,r-'1). ,I,\'i rtria"

196r. l-iri: u-qe t,i.ul1'ate irs lin e\tcrlllll tlectr,,il 3i.r'it()r lL) lonl!

'ulf idr'. uirich l;cutttulatcs in thc enrirolll.tis-t-il. i::til cranlple oll clissinril:,ttor\ reduction proccss anri linacrohic re rpiration. InJ()nrFlifi\on. the rr-ductitln of sulfate 1()r Ltsc iti ritlliilt-t aiid and

It-oteiii bir,:r niii.':is is describ.'d as an assinrilatorr reduction

ilroce\s {.sdr' sri liort /0.Jt. Other nlicroorgullisnlt hare been

ioLrnd Irr clirr) i'.lt tlissinliltrtt n elelrenii.ll sttlfur retllrclion- These

;ncltr.j: l)<'.stt 'lt,ri,ttiol1.1.{ {.\i, pp. J95' 9r)1. thCril)i}t:liiiC afChaea

' \r ( r r;(i/)r('/- -'' r ,. .llt,l alstt i-r antlbir.i.-'rilr in i;l llc:'lliine sedi-

incnr\- SLlltltc i\ snotller criiical interrrlr'iiiatc tiliit ciin be reduced

l() \Llij--rJc br lr "r

ide variet-r ol nlicr(]()rgirni\ril\" includin-u .'{i-

:(,)'()n;tlt;ti: '.nd Ciottridill//t. i.ls \\ell a: 1)t'.rtt1ii,r ilr,''io and D<'sul't'tttttn:itt'ulttrrt. Dt.'tillr'tt ibt'ro is usilallr considtrr:d li: an obligate

tnterobc. Rec.-nt rese arch. hou ever. [t'is sitrr* n th;.ll this interest-

ing organisrtt also respires using oxvgen. uhen it it pre'ent at a

,iissolr ed trxr Se n level of 0.()+t..In etldit jon ir) tlte \en' inrporlant photolithotr(rphic sultur oxi-

tlize rs -uch lt: Citntrnrtlitttn trnd Cltltttttlirrirr. u'irich t'unction under

\Irict a1n:ier()bic conditions in deep \\'atcr colunln\. a lJrSe and var-

icd gr-r'up rrt t,aiicna ctrr\ ()r,lt aerobic ano\]genic photos]'nthe-

sis. Thc.e acr()L,iJ ittl()\\ Senic pht)t()trt)ll'ls tl'e bl lcritthlt-rophr ll(/ ilnd a.ir()ten0id pienlc'nts atlrl are tbur,d in Illariilc altd lrerh'nYater

cnrironrttcnts: thc\ arl- olien components of nlicr( ial tnat com-

ntLrnitia\. Intponant gtnera inc]r.rde Ertlltntrttttttrtt. Ro-scr;aocctl-1.

l1 t rp lr t n tlttt t'trl. and Roser.t luc t c r.

"\1inor" coillpounds in the sulfur c) cle pla\ nlrior roles in bi-olosr. An c\er-llent example is clirrtethr l:ulfoniopr,..pionate{ D\1SP r. rr hich is uscd by' bacte rioplanktt)n (llcrating bacteria) as

a suliur solrrcL- f()r protein svnihesis. and rrhich is transtormed to

Nutrient Cycling lnteractions 597

Figure 28.20 The Basic Sulfur C1 cle. Pirotosr ttll.tr'tic

and chcntos\nthetic nricroorgani:nts cotitrihLttc t0 thL- cn-vironrnental sult'ur cr cle. Strli'ut.' ittttl iullitc rL'(luctiorls

carrie'cl out hv Da.\-rl1!)tviltrirt linil rclalcti nliLr'()()r:riuli\rt)\.

notc'ci u ith pltrplc artru s. are tli'.irtliiltl()l\ ilr(r(c\\cs. Sui-late reductittn also can occur in assitnilutLr;-) rc.lrti\\tt\. tc-sulting in r-rganic sr,riiur lirrrrts, E.lL'Ittci'ttirI .ttitttr I'etlttctiot.t

to sullidc i: crlrried out bv D..vI1fit rttrrt,'rt,i'. lhcrrtttrPililicarchaca. crr cvanoblctc-ril in hr persalinc .c.litrrctrt:. Stllftrr-

oxidation can be can-ied out br rt \\i(1!- riltlgc ol lrertri-tic

che nrotroph s and hr eerttbic atttl tilt;.tert,l. i i i)h()t( )l r( )Jril \.

dimethylsultide tD\'lSt. a rolatilc sLtllttr f i,rtr; ihlt clrrl llftct at-

nrospheric processes.

\\'hen pH and oxitlatir---i.i-reduction arrrlriilri)l\\ iire l'lt\ irrlble.sereral ke\. transtbrntations in the:uliirr.ra;r .r;.,, (,.JUl li\ lhe

result Of Chc_ntical reactions in thC absr,nit Ii irtr..:.,.)(ri.r,lini.rit.. _\n

irnPrrrtant exalttpie of such :n ubitltic FI-r).J\\ ,' ii.tt. ,'tirirriirrt't o1'

sultlde to elernental sult'ur. This 13(gi pllee ;.ipi.iir ili ii li.utralpH. u'ith a half-lit'e of epprorinlttei\ l() ilrrtirir': t'()r. rLllllde ei

r0om teml&-ralure.

Nitrogen Cycle

Several imponant aspccts of the ha'tt irrirt)r:,';-r 'r':,t ':. ili L.t

discussed: the prt'rcesses of autr)troPilii nitril-icati,rt:. e: $e ll rt.dt'nitrification and nitroten firrtron rligurt lli.l I t. ll .h()ulrl

I'e emphasized lhat thi. ii a "ba:ic" niii,,-lcir -r ilc. .-\llit,,Ligh

n()t mentioned in the ligure. hetr-rotroph'.ltll .-lil ,\ ,'Lll iritril-i -

CatiOn. and some Crf thc-se ha,at,1111-rphr a()ntltiilc rlitt it-i.-rli\)r)u ith anaerobic denitrilication. thus oridizirrg rrllIllrrniLllll i,ttlto \.O and N: u ith clepresred otr scn Icr e 1.. l'lit (r.cttrr.lt.!-of anoxic ammoniunr ion oridatiorl {liniilrlrl\)\ ir tirr tcrrl-, Ll\L'd

forrhe comntercial Proce\sinlcans thltt Ilittillclllltt is tttrt clllran aerobic procesr. Thus as g.e learn illl)l-e iii-\'Lli tile l'iolr'o-chemical c)'cle\. inclLrding thlt of nitr()gut'r. tltt .itttIlc eriir-:of earlier t€\thr-lirks i.trL- n(r ltlnger liaetlrlll. l'ci'l-c\e Illlilitril\ \')t'

biogeochemical proccss.-s.

Nitrification is the aerr.bic lrocess i.l1- Atlttli,,iti'.trtt irrn r\11.- )

oridation to nitrite { NOr ) and subseqlreltt nitrit.- or.i.lrtion trr tritritlc(NO.-'). Bacteriaof thcur'neraA'itrttson:rtrttt.t ltnri .\.iirirrotr.r((t1.\. t()r

example, plav irnportant roles in thc- tlrst stel. til!i .\'itntlttL-tcrltnt|related chemolithoautotrophic bacte ria canl oul tlti sCu()!ttl stctr. Rc-

centl-\'r\tll?).ra)ntotiLt.\ etrttttJtittt has been tiruncl tr, rrridizc attttrtonirtt'll

ion anaerobicalll to nitrite anri nitric oride rNO) u:irrs nittosen dioxitL'

'i"%.o.,Sulf uroxidation

AlteromonasClostriCiumDesulfovibrioDesulfotomaculum

Suliatereduction

lassimr aro:y)

SgaChapter2Bl",licroorgar-rismlnteractionsandMicrobialEcology28.22

Figure 28.21 The llasic Nitrogen C1cle.

Flous that ttccur predotttirtalltlr tttlilct' ltcrt'hic

conditions arc n()tL'Ll u ith Llpr'tl lll'l ()\\ \. .\ttllcl--

ohic proccssc\ Jre Il()tcri ''1 i111 5lrliti hr'l'l lit '

rorr's. Processe. tlccrtrritl:.1 tttlclc'r btlllt i'lal (rlrir

and anaerobic ctlnclititrrl: arc Illal'kc.1 rr ith

cross-barred rrT0\\ s. Thc enlLntr.rt0\ I'CliCiirrtl ol

NO: and NHi- to r ieltl \. is :ll()\\ tt ltrll'or-tant genera conlributills t() thc Ilitr(rge Il e r e lc

are gir en as exartrPlcs.{Many genera)

Drssrnrilatlonand l'lineralization

( NO] ) a: an aCCept()f in a .itnitr-i t iclitii)il- I J r,rl.tl I ti.1!lir)ll. I n rt.itli-

tion. heterotrophic nitrilication 1,1 lru.tcii.i ;rrtd 1ir;lri cotltdbutc:

signiflcantly to thc:L- pl'oce \scs itt ltlore acitll; t-nr trL'lllllctlt\' \

tliaiiirn ::,.1 nitritler-': I r':

The process of denitrificatiotr rcqLrirc: e r-li1-l'"r'etlt \et (rI en-

vironmental contJitions. This di::ilrlilrii(tr'\ lrt)ec\>' irl $hich ni-

Irulc ir used a. ,n r'lfatr')l) it.(L';-:': i:. .ltl.,.'r"r'l; 1!''1'ir::liillt.

usuall) involves heIcr0trt)Pils:t-t.il l:: I'-st'irdt'tt:'"t'tt tlt't: iiri.|i-

e rrrr-r. The niajor product: tri dcrrit|ii'i--iiit)rl illi'ii.:i;. ni11'0gctl gli:( N1 ) antl nitrous oride ( \'O t. allh('ii!li rliil'il" i \O i ll1\() cln ;'L'-

cumulate. Nitrite is tlf enr irtinnl.'lt;.:il ;.iiili-lt lt'!-irutr it ulLtt ut'n-

rribute to the lbrnrati()n,rf car.ini)!.Jnla ltitr,.r::rlIi;'ier. Fillllll.nifrate Can be transfOrmCrl io alllttl,rilllr irt ili.sitllllrt()r) r!-du!ii()ll

h1 a rarieti' of blcterill' inclLrtiilll {ttt'i)c;tlt'r'ri:i ";'lilt'riit' t'r:r'

Desul.ftribrit, sPP.. arld ('lr'.ttt'itii:tt':.,r(\airirii!.i ,1|. 1 S---' '

Nitrogcn assir:rilltirllt ()cLtlr\ \i;l:ll ii;,rr:;tii;' I::rr''|r-li;l :' i:-i'ias a nutricnl and incllrpor:rtc(l llli" :l;"i :i:i'lr':-: f i:liriii'1\\ '.\1li-

monium irln. becausc it i::Llrcadr :'c.ill.cd- d.ll] 'Dc .ilI'c!11\ in!()r-

porated u ithout nrlrjtlr encrgl Ciltlt Ilrr\\ i\ ui' \'\ illit tlilri:lt i'l.rirttilatcd. it murt hc rt.;i:ied ". . ., ':-r..i]..::,: ::.-:-\ (\:'-l:'

diture. In this prtru-ess nilri1!- tllar :,--lltt;'.llltl'; li' -. i:dll'i'llt lrll'l-

Nitrogen firation cln be caiiiL-d trttt br rerrrbii or lllaL'r()bic

procan olL's and dt>es ll()l l)!cIll- iil aLl.l,; r "'rr''- L ll'ir;' itt.trbi"r 'tl-tlitionsauidc'rangeot ll-cc-lirirlr;1,i.:'ti';r'; -!lr!:;: t \lti1ttlt'i1 111'

A:0spirillunt) contributL. lo tltis prir.c". l ir.lcr':1nlil'rr)irie a(rl'r!li-

ti0ns thc nl()st iInPt)rllrnt frec-lir irll rlllr."i'-;r i-irul' ;'rlc tttiitthlt'cll' the genus C!tt tritlitutt. \itrttl.'ll l'ir:.,ili'tl il\ a\ itll()bi'tclcrilt

such as .lttuhttt'ttti lttiLl ()i.l1/rtl0iii, 'l,il l.':'.1 l" lili :r'.;t.hiii''ltl Iiacluatic en\ irontlcnt\ * itl-r pitlogcn. 'l'iic.; rrLrtritnt-cnrici'tllcltt

processes are discu\scd in cllaptcr l!r' ir; rrt:'litiotl' nilrogcn t'irlt

tion can occur through thc actir itiet ()1 irirai.T'lll thet ticr cloP :r tlt-

biotic associations rvirh plirrtt.. -f|1grg. ;1'rlreilitiotls inelLltlc

Rlriltbium itnd Bnttlt rltiattbitrrrr ri ith lcSultlc' . [:rrttikitt ill a\\()ci-

ation $ ith rnan\' \\ oodY shruhs. itlld.-litrilrrit r;.1. \\ ith .'1:o//zl' a rr lt-

ter tern intp()rtant in ric.- culti'. lrtion' rr rL': i

t-.,..,-,

N itrificationilJllrosomonas.r\ifrosococcus)

-l-hc nitrosen-tlxation proce \\ inr ojves li scquencc r.r1- rcdttc-

tion stcps that require nla.ior enerqY e\penditures. ,{mltionia. tiie

producl of nitrogen rcduction. is irnnlediatelr incorporatt'tl initr

orsanic matter as an iill1ine. Reductil e processes are e\trL'll1el\

sensilire to O. and lllust clcaur tlnder anaerobic corldititltr: ercn

in aerobic rnicroorganislll-s- ProtL-ctic)tl of the nitrogt-'n-flrin" en-

zr nrcs i,r achie\ed br ntcanr o1'a r:''ir-l) ol trl,' 'ilr''ti'rtrt. incirr'-l-

ing phl sical barriers. a\ L)ccLlr\ \\ itil hcter"cr rt' ill 't'tlteur an0bacieria \see st't'tittrt l/.-ir. O- \ca\ cnginS ttlolecttlcs. alt.i

hish rilt." rrl rrtctabolic uctir itr.:: llr. tr

As shou n in tl-curc- lti.l l. nlicrooi!ani\nls hlil'e bcclt istllatr'tl

thrt can couple the anaerobic oridatitrtr ()f NHr \\'ith the rcdlrc-

rion 0l \O1-. to prodtrce 'Jr\cr)Lls nitro:ctt' irl lrhat has hct'rl

tarnlcd thr' anammo\ process ( ttriotic (litili1()nia r'-tidalion t. .\ttcrlrnrplc i. an anaerohic chenrolithollttttrtrtrflt. tound to t'r- Lt

pi:init()rn-\cctc (.!(c .\{'( Ii(r,t ) 1.11. thlr', ha: hccit trlitttcd Bn'i t;.iitrt;r;it,)int{,.\i(ii"nr.s. This ttlil\ Pr()\ idc l.t lll.'.rll\ br rl irich tlitri)!cll .iillbc rernoted from sc'uage plant cf11uenl: t() decrca\r' nilrr)SL'll

llrr\\ to sen:itir e tieshrr atcr and ttlarine eco\\ \lalll(.

1 . What are the maior oxidized and reduced forms of sulfur and

nitrogen?2. Diagram a simple sulfur cycle.

3 What is aerobic anoxygenic photosynthesis?

a. VJhy is dimethylsulfide (Dl"'1S), considered to be a "minor" pan

oi the sulfur cycle, of suth environmental importance?

5 What are nitrification, denitrification, nitrogen {ixaiion, and

the anammox process?

lron Cycle'firc iron clcle (figure 28.22r inclucle: sevcrrtl ditlirent generx thilt

!lfr\ oui iron oridatiorts. transtilrtrlinS tcrr-oLrs ion (Fer ) to lcrrici,,n ( Fcr - ). Tltiobttcilltrs f errut,.ritlurr.t carrics orrt this process under

aiitlrc conditions. Gullirttrel/rr is actire ltrtder neutral pH condi-

rirrns. and Sul.fitlobu.; functions undcr rcidic. thernlophilic corldi-

Assimilatorynitratered uction

Organic N

No.

ENitri{ication(Nitrobacler.

Nitrococcus)

(Nlany genera)Pseudomonasdenitrificans

Denitrification

N, + NrO@N2 fixation

(Az ot ob act er. C I o st ri d i u m.photosynthetic bacteria)

Geo bacter metallired rc en s

Desulf ovibrioClastri,lium

t

28.23

AerobicNeutral pH = GallionellaAcidic = Leptospirillum, Thiobac':,us ferrooxidansAcidic, thermophilic = Su/folobus

NutrientCyclinglnteraqtions 59!)

Figure 28.22 The Basic Iron C1'cle. A sinr-plitie d irtx cl cle s ith examples of nricroorganistlrcontributing to these oxidation and reductir.rrproce\sl-s. ln addition to l'errous ion tFel-) ttxitla-ti,rrr urrrl lL'r'rit. i()n (Fe'' t rctlucliotr. ItuLtte tite( Fc.O. ). a mixed valence iron ct>mpound titrnte d hr

nlagnetotactic bacleria is inlportant in the iron cr -

clc. Ditl'erent nricrobial groups carrv out the clrida-tion ol terrous ion depending on envirttnrttentiilconditions.

Fe.O.-FFe"O. \.-

F e rr i b acte ri u m I i m neti c u m

G eo b acte r m etal I i red u c e n s

Geob act e r s ul f u r red u c en s

G eov i b ri a f er ri red u c e n s

Desulf uro m o nas acetoxi dans

Petob acter c arbl nol ic us

Sh ew ane I I a p ul ref ac i e n s

AnaerobicAnaeroblc PurPlePhototroPhic bacteria

lions. \luclt ol the earlier litcraturt' sur!-"tr-d thltt lriillri'1,,"1 '",,-:ra could oridize iron. ttlcludtttg 5ltltutrLttiltts and I'altirt!ttrir.'I-hcsc tso gcrl!'ra iire still tenricd "iron bitcterilt" bt ln:Lnr llt)ti;'tti-

;robiologist.. Coniusiitn about thc- role oi lhcse -!u-nei-l rcsltli.'cl

iloitt rhc (rcurrence of'the chcmical oxitilttitrn of lertlLts ion t() Icr-

ric ion (lirnnins inrrtlublc iron pr.-cipitate:lat nelltral pH raiucs.

r,. lrere nricroorganisrns also grorr. otl or-9anic substratL-s. Thcse rlli-

;roorgan i:tnr itre no\\ cIlrs:itled as chentoh.-terL)tropll\.

Rccentlr nticrolres have bcen lilund tltat oxidize Fe l u'itlr

r-}itralr- a. an L'lcctr()n acceptor. including tht interetting ttlier""r-!lrnitttt l)!(l!i(tt1,.\()ttttt suillunt., t',,111111trp1t {.tL't' 1t. 9rt ) ihlll .Jllri:o I,lre chlorate ils an clr'dtrorl ilaecptor. Tili: prt'ucr' rl"!ur' illaquatic scdimcnrs sith depressed lcrels o1'orrSen illlcl Illa\ ilc

"rnolircr r(iutc b) *hich Iargc' ,'one\ ol'tlridiz.'d irotl ltllrc ltccLt-

nruluttil in cn\ ir()nritent: u'itl-t lon cr oxr gctt lcr els. Biindc-d il trll

l()rnruil()n Ihrl occurred \\'hl-n xtlllospheric orl'-uen leVels u erc

L,cginning to increl:e at thc end o1'the Precarllbrian era lllar bc

u'r'idencc' of increased iron bacteria activit).lron rr'Juctit)It ()ccurs under anaerobic contlitions rerultinc itl

ihc ace utttulation ol-l'crrtlus ion. -\lthough Illittlt ttriir.'t)l'grlni'lrr\

-urr rcdue c stnall amounts of irttn dLrring thcir ltletabolisnl. tllost

ir()r] re(iucti()n is carried otrl b) \ilccializcrl irort-r.''pirirll rlti-

.r()r)rgrini\nrs such ar Gertbur'lt'r tttt'tttllit't'tlttct'rts'. Oet,ltttt'Icr:ttl''itrr((lttt'('/!.\. Li'rributtcriutrt iirttttt'liLitttt. alld Sltttttttttllri

,i1utt(.1(t( i('il.\. ilhich can ttblaitt cnergr tbr gro$th olt 0rgatlic nlat-

lur usilig terric iron a\ an o\idan1.

In lddition to thc\e relativclr sitllplc rr-ductiol-ts to lcurlur ioll.

\()n)c nrit!netotactic bacteria such as Aqrrusltirilltrttt tttuq)t(lo-

Ittt titunt {.st't,sacliott -i.-3)transfbrrtl extracellr-rlar iron tcl the ntirecl

r alcncc iron oxide mineral nta!tnL-titc (Fe-O,) and collstrLlct intra-

iellular rliagnetic comPasses. Funiterltlrtrc. tlissiltlilattlrr iron-

i-cclucinS bacteria accuntulate nlaqnctite as tn extracclltriar produet.

\lr,rn.-tite hl. been detected in sediments. u'here it is pre:ent

rrr plr-ricie. sinriiar 1() thosr- tbund in bacteriu. indicatin-g a longer-r.i'In .(rntributio:r rrf hactcria to iron cvclinq processes. Genes torn]lrgr'rL-titc \) ntllc\i\ har e been cloned into other ()rsanisnl\. cre-

:ltin-g nes nrrgn.tie 3ll\ \L'n\ili\ e nlicroorsani\ms. Ilagnetotacticbactc'ria arc no\\ Jc.cribed as magneto-aerotactic bacteria. duc

to tlrr-ir u'ing rnrqneric lields to migrate to the position in a

ho! or s\\rnlp.,rhc're thc o\\sen level is best suited fcrr theirl'unctioninS. In thc last decade ne\\' microorganisms havc bcen

tliscr,rcrc'd thirt urc lerrous ion as an electron donor in an(l\\-:criii iriioto:r nihesi:. Thus uith production of terric ion iniiIirrei lnalrobi:1r')nes bv iron-oridizin,g hactcriu. the slage is

\ct t()r \ub\cque nt chemr)trophic-based iron reductiofl. SUCh ]:br (it oltrrt i t'r lrnd S/rerr ont'llc. cretting a strictll anaerobic,,:.idutioni r.'.iue ti()n c\ cle 1'or iron.

fu/ianganese Cycle

J'hc' ir:rpo..-ince o1'micr,xrrganisnts in nransanese c\cling is t\e-

er)luins nruch bctter appreciatc'd. Thr' miinlancse clcle (figure

2ti.f-jr inrolrcs thc lransiomlation of ntanganous ion (\Inr- ) t,r\lnO. tequivalcnt to man-{Ianic ion Ilrln'-]t. *hich t^-curs in hr-drothcrnral r ents. hogs. and as an imprcrtant part ol're-k r arnisher.

l,<,1trtttltri.r. .\ rtltnltuttt't'. f'cdornic'ntbiurtt. and thc inconrplet.')rehaiir.terized '-.1[t'rrt!lo.qenill//l arc inlportant in Iln]- trridltit'n.SitL,tr'ttrtcllu. ()t lrtcter. attd other chetnulrganotrophs can cafi.r

out the conrplcntentan. manganese rt-'duction prcrcess.

Other Cycles and Cycle Links

\licnrrrganisnls can use a * ide varien of additional metals as clec-

tron lcceptors. .\'letals such as europiunl. telluriunl. selenium. and

Unknownichemical

magnetotacticum

Chapter 28 Microorganism lnteractions and Microbial Ecology

Figure 28.23 T'he Nlanganese C1'cle,

Illustrated in a Stratified l-ake. \'1icro-

r,r'sanisnts make tttanr intlxrtlant contribu-

tii',n: to Ihe tnang:,rnesd Cvcic'. .\fii-r ditiirsingil-onr anacrobic rpink) to lerobic (blue)

z()nes. nllnganou: ion (\lnl') is oxidized

chL'rlricallv and i.r tttanr nlorphologicallvt.listinct r-nicroors:anistns in the aerobic rva-

ter crrlunrn to man-9anic s1i{g-i1tpQ.tlVt.\alL'nce equiralent to J;. \\'hen the

\1nO- r\ dilJuse> iirto the .rnaerobic zone.

hectcria stlch ils Gt'ttlxtcter ancl .Silt'rr'rurc/1tr

ciirr\ out the ctttttplettlcntarl redr.rction

pl'()cL'\s. Sinriilr proccs\es occur ilcross

lucrirbiclanaercrbi l trattsititrns in soiis. ttluds.

ancl othcr enr ironntcnts.

Anaerobic

A,-t,".obacter .-gl

Lep )thrixdiscophora @

"Me:zi!ogeniun" @

PeCcmicrobiun @

Grccacter Q

She*'anel/a 13

rhodiunr catt b,e rcduced- Imp,ortant r-nicroor-uanisms that redu.e

these metals include the photoorganotrophs Rhodobacter Rittt-

tkt.sltLrillturt. tnd Rltotlrtpseidontotrus. For selenium. Pseudornr'ttLt's

\//rI.-('/r. Tlt,ttr, r,t :t.lt'rtttli.:. end lli,lirrcllu .sttct'itttt.g<'nes are JLIi\eStich r.-ductions .an decre&le the to.ricitl" of a nlt,'tal-

Thr- .,ticrobiri transfornration of phosphorus involves prine-!

rilr the trsriql-\rtfiii,ii(Xt of phosphonr. 1rf valence) from sinpie1111|11rpfiprIirure l(i \ ari()us more conlple\ tornis. inciuding

lrirlrphlrspllltcr i,,und in melachronliitic cranules (st€ P- i9t- ALrnique (and po:.iblr rnicrobial )pr<rduct is phosphine 1pf{-,rriitllrr -l valenc.-. uhich is liberated tiotn su'anlps. soils. and ma'l.inc

rcrit-r'r. and ghl.-h ignites shen exposed to air. This can thr'n iq-

niie l-trethan.' pri{ueed in the same environnlcntl The produali,in

ol rrethane i,.-r inlcrobic microorganisms uill be discusseil in

.:hlpir'r 19.

I-lri inc d.:.;a:n:J the sull'ur. iron. and mansanese c\c1c: il\1'uliclir,nin: in.i;;*-ntlcntlr. it is inlporlant to again emphasize thlrt

niinr miarr.r,r,q3xiims rrietabolicallr link therc' crclcs bl u.inlc,,nlli,nl) .har.',-l oritlani. and rrduclants. For erarrlplc. \(rnle

sLr1l-ere-reclue inq illie roorqanisms c3n rcduce F.-'- u.ing f{' r-r1- 1';-

::linic maltcr ar an clcclron donttr and rlso can oridizs' c'lenlenill:ulfur ro sullate shen N{n'l\' is preseni as an electron acceptt)r.

Th.' \1n It '-,1e pendent prr-duction of sulilte under anaerobic c.tn-

tlitions. e arricd out bv Dc.ttlf(tbulltus prrtltirtrtic-tts' provides a ri.:rr

r,i Irnk sulfiir and ntan-uanere c1'cling anaerobicalll.

1 . Y,/hat major forms of iron, manganese, and phosphorus are im-

portant in biogeochemical rycling?2. \'/hy is Aquaspirittum tonsidered to be a magneto-aerotactic

bacterium?

3. Slhat are some important microbial genera that contribute to

manganese cycling?

4. V/hat is phospnrne? Under which conditions will it be pro-

duced?

5. How can microorganisms metabolically link the sulfur, iron,

and manganese cycles?

M icroorganisms and [4etal Toxicity

In udditjr.n t() nt!'tuli such as iron and nlanganese. u'hich are

lur!elr n,.ntt,ric ti- mrcnrorganisms and animals. there are a se-

rirs trt'illci,1l: tll.rl h.,rc taried to\ic c't-tects t'rn nticrortrganisntrrntl ironr j,.iir.'rnii. rr;rinral:. \Iicroor:tanisrns plal imponant rol':srn nroriiir iirs thc ti)\:-it: ol lhr'se ntr'tals (table 28,6).

-firl 'r:,.'i:ilr".r,n oc crtnriderr'r1 in brtiad cate-gories. Tha"iroi.li ,i,i':.ri*" li;r'r rr,.t t,r crr)\\ thc rertebrate bltxtd-brain bar-

rie r l.irl i.r;: h:lr c .lr.iinit clia!t\ t,n ttticroorSllnisms. \licrotlr-grrni'ir:. irl\() ciilr ra.iLrcc- it,ttic t'ontts of noble rnelals to thr-ir

clt'rrtcnlrl iirrtns.l-i:. -r.r,n.l Sr,,i:l in.'lu.ie: tnctuls or ntcttlltrids that nticrortr-

,riliti\nl. r':in rltclh\ i::lc' Ii) ti]rnl nlore nlohil.' prtlducts callc'd(\1.j:r:tt);l-ra::11\. Srr:t'r-- ,\:_liint)n',!-iili\ aJn ar()s\ the hl0i,tj-bruin har-

i'iti Irll.1 lrllc.l iitr' . illlrul il:r\ \)u\ S]'.le nt ()l vc-n!-bralc\.(-)i!i:nr1rici.li\ c!rii.rr:r,:il-iti,ll-t:lttei fxrnds.-l-itc-re b0nds are theirLlilrrllr:',r1.''111 1 r irl I Jl.r: :lLtr'f i.i l,\.

i-1r: r.-rlrcllr.. .\ .'.,r i\ r,l t:rnicullr intc'rest und illustratc:ililriri slr:rr.ratcri.tr-. ,,i lhrrre ntciulr that cart be ntethr lated. i\tr'r-aLri-\ !()rlll()LlnLl\ \ia;i rii.k'lr u.cd in indLrstrial pr()ces\es ()\L-r

th.' centuncs. One hl,. ()nl\ [o think rrf Le$ is Carroll's allusicln to

this prrrl,lern uhen h.' *rote of thr- \Iad Hatter in Alic'e itr llbu'It't iLiltti..\i thlit tilra inircLtn $ lA uscd in thc shapinq of telt hats.

\licroL,r-sanirni\ nralir) laled st,rnr' o1-Ihe ntcrcun'. thus rendering

il r.Ilort lrr\it tr,Ihc halnlttker\..-\ rlc,, astalins rituation de re lopo-.d in strttth*cstern JaPan

uhe n IarL.--rcula nr:ruttn poi.ottinL occttrrcd in the \linarnataBltr re Si,,;r i.c.;.rir.r ,,i iitdu:triai llte r.un rcle ared into tlte nlarinL-

dnVir0tilrrcnt. lrror-Llinre nlcrcur\ that accuntulated in bottonll.nucls ol thc ber u rr. ilrcth) lated hr attatrtrbic bacteria of the

!lenrrs f)r.'rr1ll'1 iltTilt ifigure 28,2{t. Such nrcthl'lated mercurvlirnrs arc rolltilc and Iipicl soluhlc. and thc mercun'concentra-tions increercri in thc f irrd chain (hi thc pr()cess of biomagnifi-cation ). 'l hc nrcriuri t us ultirnately ingested b1' the humanpopLrlation. thc "top c()nsurrer\. through their primarl food\orlrlre tr.h-leadrng to \c\.cre ncurological disorders.

28.24

6(,2 Chapter 28 Microorganism lnteractions and Microbial Ecology

The thircl troitp ol'rltetals occurs in ionic lilrms directll ttrric

to nticroorsanisnt:. Thc utetals in this uroup also can lrlltct n-it'rre

coniplcr orsanisn.rs. Ho\ er L'r. plasnla protcins re act $ ith the itrnic

lirr-rns 0t'titcse nrr.rlls and uid in their c.\crL-ti()ll ttttlers excer.iYc

I0n-rt-tcrnt c()t)ta.r aud incestion 0ccur. Relatir e11 high clo:.-s of

these rnetalr arc rr-quirecl ttr caLlse lethal eftects. At l\)\\er concen-

lrations manv of thc-se ntetals serYc its reqLrirecl trace clenlcnls.

'1 . What are examples of the three groups of metals in terms of

their toxicity to microorganisms and homeothermic animals?

2. How can microbial activity render some metals rnore or less

toxic to werrt-blooded animals?

3. Why do metals such as mercury have such ma.ior effects on

higher organisms?

ep rHE PHYSICAL ENVIRoNMENT

\{icroor_canisnts. :-s thev inreract $ ith each other and li ith other or-

ganisms in hiogetthetrlicai c1'clin-e. irls'- are inl.luencr'd b1'their im-

nrediate phl sical enr.ironment. ri'hethe r this llright hc \oi1' \\'ater' the

deep rnarinc enr irontltent. trr a plant or aninlrrl ho:t- lt is inlptrnlnt

ttr -onsiderth-\i'Jitlc!'n\ironlllenl\\he'':l'tlicrttttrSurisnt'inter-act \\ ith each tlther. othe r tlrgiLlti:,ils. l-tlld the phr:ical enr.ironment'

The tr4 icroenvi ronrTlent anc t'Jiche

The sprcitic phrsical location ola nricroorganisnr i' it' microenvi-

ronnlent. lrt this phl sical nlicroenr irt'llment. thc llur .'i reqr'rired or-idanrs. rccluctanl.. and nulrients ttr thc' .icltli.ti i'l-rtion oi the

micrrxrrsanisnt can be lirnired. At the serne 1ip]s. r,,, 1r.ir'prcxlucr inav

not tr rblc to,.iilii:.e ltu ar tlonl the nlicrtr.lrsani'i.l-i li iate s sutficient

Itr arrritl groutil inhihiti,ln rr high \\r":ta P|.\iu. l 'i'njcntmlions'Thcsc tlurc. and !rr,1ie tlr. .i.ate a uni,.iuc nichc. u ri;h includes the

nricrtrrganisnr. iri phr sicll habitat. thc time oi rcsour--r' use- and the

res()urcc\ lilailliblc iirr nticr.,hial 9;<l* rh and functrttn tfigure 282-<).

This phl .icaill :trllciurcd enr ironlticr.ii :'llstt 'utl

linlit thc

predalor-r acrir iiie s of pri tozolt. Ii tl-re rllicnr.'n\ ironnlent has

pores \\ith diLrmeter,s oi I to 6 prr. bactcria in the pores riili be

protected frorn predation. rlhile allouin-e dillusion of nutrients

lind ri a:te protlu.-ts. Ii'the ptlres art' lxfger. , -'rhapt5 Sreatcr than 6

pnr in diantcter. ilrotozoi iltar be rblr' to 1'eed trn the bacteria' lti\ irnportrnt to .'ntphasize that microorganisms can crexte their

or|n nricrotrtvir,',l.ttllents antl triches. For erarllple- tnicroorgan-

isnt: in th. intcrl.r ol'a c..i,-rnl har e trlarkedll Citterent microen-

r ironn.ieni. an.1 nicil.': lhan th,rrc oi tl: :an.le microbial

population: locaied ott th: surfaee trr edgc ot'thr- colonl' \1i-croor-qani\llls al\a) call a\\L)aiate $ith clals and Lnt inen micro-

habitats crlletl "clay hutches" 1'or protectiort lsae .set-riotr 1)-1).

Biof ilms and lviicrobial Mats

.A.s noted in section )8.3. n-iicroorglnisrns tend to create their o\\'n

nricroenr ironments and niches. bl iornling biofilms. These are

28.26

Anaerobicregion w ililsullide

Sulfideconcentraiion

II

Specializedniche

{or aerobic sulfroe-oxidizing microorganisms

Figure 28.25 The Creation of a \iclre from a

Nlicroenr-ironment. As shou n in thi' illtr'tr-rilLr11. t\\ () Ileitrb)

particles create a phr sical microenl irotlnlent 1t)r pt'r:siblr- use br

microor,ganisrns. Chentical gradients. 3: \1.ith t)\\'gcn ironl the-

aerobic region, and sulfide tionl the anltertrbic re!i,'ti. .rcrtc :l

unique niche. This niche thus is the phr.ie ll :nr ironrr.tctt! ancl tltt.

resources available for use L.r speeirilize.i ucrr)bii:Lrliide-oxidizing bacteria.

organized microbial \\ str'i11\ consi'ti;lS 0l- l;'.r s'1r !rl' lllicrohi:ricells assrtiatcd qith \urliicc\. Such li,.,l'illli\ irl'( .rrl illlP(rri.ri,i

faCtOr in alntOst all areas lrf lticrgbitil.)!\. a\ :lt,,''i n in l'igUrt28.2fu- Simple biotllms clc'rc-lop uhin l,'licr'-',)l-'l.rrrl\rll\ .rtili'i:and form a mono'larcr ol ccll:.

Depending on thr' paniculrl s1l.'r,'i-'i.ii !r"\\lll .ll\ lr"liril!'i(light. nutrients pres!'nt. and ditfutit,n r:-itc:). ihc\e blr'irlrli: r.rrr

become more cclntpler u ith lar c'rs (ll (\i-j.:11i:ill' tti .iii'l'c:.'nl lr P.l'( fi gure lE.l6lr). A tl pical eranlplc u r'.: l-i inr t:l

" C pir' rtr''" titltct i'

organisms on the surt'ace. facultatirc aiictlli,0:.'q.lll,rIr,)ni' in tll-middle. and p,-rssiblr sulfatc-reducitls ltlicrit.trgrttti:li'.' \)ll thc

bottom.lllore complex biotllnrs cen dtr.lt)p :.r t()rII l loll:--

dimensional stmcture (X. \'. Z. and tinrc r rr ith --el1 rsri-J::iit.t. irl-

terstitial pores. and conduit channei. tlrsi r.' lS.lt''. t. Thr'developmental prcrcess involve s the grori lh rri-iltlltahaLl nlicritLlr

ganisms. resulting in acculnulalion of ltlilititrrl:.1 .tll: ()Il the \tlr-face. together ri ith the cot.ttinutltts trapi'ing litld :;llillohillzati()ll ()l

tiee-floating microorqiLnislll\ that nl()\ t (\1' tr ille crplntlitlgbiofilm. This structure alltlu s nlttrient. trr rcr.h the bionla.s- and

the channels are shaped bl protozc'rlt th]t gl-;l/. ()n iract.ria.These more complc'x biofilnrs. in rihich ttti.lot't!ani'nl' crL'-

ate unique environments. can be obserrctl br the usc ol cont'trcal

scanning laser microscop-r' (CSL\11 a: discu.red in chepter l.The dirersity ot'nonlivin-s and living surt'rtt:. lhat crn [.rc er-ploited b1 biolrlrn-fo.n, i11g 111ir- roorrrtnirnl' r nclttdc surt'aces ill

Oxygenconcentration

28,.2i Nutrient Cycling lnteractions 6(}1

Examples of Microorganism-Metal lnteractions and Relations to Effects

orr Mic anisms and Homeothermic Animals

\oble ntctal:

\lctais th:rt lirrrn sirhiecalhon nc'tal bi,ni'

()ilrcr rnctll.

.\L

..\ u

I,1

HgSrl

Cu'1.n

Co

Silrer \{icrtxrrglnisrns cltn rL-Llucc ionic tirrll: lo thc'

Cold elemental stale. L()$ l!-\'els (rf ionizcd n]etais

Platirrrrnr releasedttltheenvironnlentharc'llntitllicrohialactir it1.

Ar:enic Nlicroorgenisnls can transtbrm inorganic and t'rSlnic\lcrcutr tilrrns to nrcth) lated tbrms. sr\nl!' oi' $ hiclr tenri to

Scleniunr bi()accuntulate in higher trophia lcvcl\.

i\lany of these nr!'lrls can be reducerl t!) alenlentlltirrnrs :rnd drl n()t tcnd t(r cross the t'itrtld-brainbarrier. Silr c-r rcduction can lL'ad tr) in.ndegrsits in the skin.

I\,lethl letcd lirnns of some tttelals can cross thchl rxrd-brai n ban-icr. reruIting i n neurtrlo-gical

et-1ects or death.

At higher ler el'. clelrrnce frrrrn highr'r rrrganisnrsoccurs bv reactitrn rr ith plx\ltla pr()leins and

other nrechani.ms. l\lanr trl thesc'ntr'tals

CopperZincCohalt

ln the ionized firrnr. at higher c(rn.!'ntrrti{}n\. tl)r'sc

nretal\ can directli' inhibit rni.r(x)rgani\n]\. The\

are otlcn r(qrlired lt lorrcr ir'|rl-('l)lriltiiln\ il\trace elements. sen e as trace elentcnti al lot et

\\'t .r n

^!!,, +

Hgo, cH.ng- I

Atmo:phericregion

Figure 28.24 .-l'hc \lercurl C1 cle. Int!.racti()n\ betu'een the atniosphere. aerohi. \\'atcr. and itnaeroiric sr-ditllent rr. criticiil \1i-

It..r.,rlLtlrle HtS

Hgo

Frg-

28.27

(c)

Figure 28.25 The Gro*'th of Biofilnrs. ilit-'lllrl:. rir n-ricro-

bial grou'ths on surf-aces such as in fr.'shr'. at.t- silJ l-llerinc .-nr i-ronments. can deYelop and beconlc crtrclilcir ctrtitpi.'1.dependin-e on the enL'rgv s()urce s that lr: ar lllr,hi.- 'it; ltlitirll e ,rl-

onization b1 a single lvpc'of bacteriutrt- rlli [)c'.c].-irillcnl ()t a

more compler biotllm u ith lal crcd nl iar\'()r::llrl i.tlr' oi' tl i ilerq-ni

t_\'pes. {c) A malure biofilm u ith cell agSr.rlrl.\. irlt.r>littltl P()re\.and conduits.

catheters and dialy si: units. u hiclt har e itllitlrrilc -(-rIl',r:Li rr itil ilu-man body fluids. Control oi such 1111;iir,,1-1:q11,.1:1' '!:',.. ilr'''i: cs

tahlishment in the.e sensitiyc nlctlicai .ji'\t:r'' r\.:j- irii',1 1:'i-iili

pan of modern hospiral care.

B iotllms als0 cln Protcci path()scn\ i.r irl l (i i. i il l r'- l lr ll i'. i r -'.ric

a t-cxus tbr later (x currencL- ol disease. (ra iJl. .1.c rll i - :, "' :.r rl i. l ll.and microbial prtxlucts lhat mar attect tilt iilrilrtlil,ri,'Si-iil :\ \iL'r]i

of a susceptiblg hort- Biolllnt: are critii-ai iti ,,.ulitr rii:tr>e> bc-

cause Clrldnr-\'diu, StttplrlocoLL-tts, anti other pathtrLe nr surr ir c

in rxuliirdevices such as cclnlact lcn:es altJ in ilclii:i::-: 5clLiti\)n\.

D!'pending on environntental ctln.litioti'. hi.rtrll:i: cltt bc-

come so large that thav are r islble and hlr c ltlrr.r'i)\-\\irir riinlcn-sions. Bands of nticroorganirms of ditltrcr)t .r )li)f\ r.. .\ ide nt a\

sho*'n in figure 28.27. These thick bit illrrr.. clilr.: nricrobialmals, are lbund in manv l'reshriater ltn.l llllrrj Ite u:t' ttr'tltllcrlt\.These mats are contpiex layercd nticrul'iai e()tllittLti:t:t!i\ ihlrt ean

form at the surlace oirocks or sediment. in ltr pcr:aiir:t anJ tresh-

u,ater lakes. lagoons. hot springs, and beach ltrce. -fhc) consist

of microbial t-rlanrents. including cyanob.lcterir. -\ ntuior charac-

teristic of mats is the extreme gradients thal are prcscnt. Lightonlv penetrates approrimatelr I nrm into thc-se cotttt:turtitie s. and

belo* this photosrnthetic zone. anaertrbir cttnditilrt. t,ccttr lndsultate-reducing bacteria plal a maior role. The sultlil.' that these

The Physical Environment 603

Figure 28.27 \licrobial l\{ats. Microorganisn.rs. throu-sh

their metabolic activities. can create environrnental sradients re-:ultin-g in la;ered ecos\/stems. A vertical se.tion of p | '1

.'11i1o

(5-i'C) n-ricrobiril mat, sho,'r'ing the various liuer: tri rnicrtrrrr-ga n is rns.

r,rgrnisnrs prodLrcc difTuses to the anaerobic iighted rLrsion. ll.]-

louin_c sulfur-dr'pendent photos)'nthetic microtrrtenism\ togrori. $1;1119 bclicre that nricrobial rr,ats could hare allo*'ed the

formation ot'tL'rrestrial ecosvstems prior to the cler clopment of\ i.l\.Lllar plants. and lossil nricrobial mats. callcd strontatolite:.hrLre trccn di.itcd al over -1.-5 billion \L'tr\ olcl (rlc f.. J11lr. \loi-cir,rllir tr'chniqucr antl stablc isott'rpc ,11!'a\urerltcni. l.ci \caii(\I'llS.5 ) are bcin-g used to beller unde rstand these unique microbiala()nrnlunilies.

1. What are the similarities and differences bet\r,/een a microen-

vironment and a niche?

2. YJhy might pores in soils. waters, and animals be impofiant forsurvival of bacteria if protozoa are present?

3. Why might conditions vary for a bacterium on the edge of a

colony in comparison with the center of the colony?

4. What are biofilms? What types of surfaces on living organisms

can provide a site for biofilm formation?5. Why are biofilms important in human health?

6. What are microbial mats, and where are they found?

M icroorganisms and Ecosystems

\licrrxrrganisms. as thev interact *'ith each othcr and other or-

-!ranisnr:. and intluence nutrient c)'clin-g in their specit'ic rricrrren-vironnrents and niches. also contribute to the functioning of

Secondary-level consumers ]'-Es-+

Primary consumers

6()4 Chapter 28 Microorganism lnteractions and Microbial Ecology 28

.l- Serr inc as lr nutrieltt-rich fottd sourcc for other ch.'n-hctcrtrtrophic nticroor_ganisllls. includin_g protozort rl

anintlls.-1 NIoilit,r ins srrbstnttc's itncl nutrients uscd in \) nlLliotic Sr(i\l

pr'occ\\cs and inteftrctions. thus contributing to biogc.ochcicll cr cling.

5. Chanuing tire aruounts of rnirtc-rials in soluble and s;-i.r.r.firrnts, This occurs either directll,bv rnetabolic prnccs<r,.indirecrlv bt, ntodit'r ing tlte environrnenr.

6. Prodr-rcing inhibitor-r, conrpounds that decrease nticrtriracti\ ii\ or lintit the survival and functioning t l plants rr

alliIIlll\.-. Corrtributinq to the functioninc of plants and aninrals thr,.u

positir c ancl nesatir r. sr rrrbiotic interi.ictions.

i,{ irrocroa nism Movement between Ecosystems\.licroorganisnl\ constantl_\'are moving and being mo\.ed hct\\ L-

---osvste nl\. This often happens naturall.v in ntanr. $.a],s: ( I ) srril::ansported around the Earth by *'indstorms and falls on land r

eas rnd \\ arers lar tiom its ori-cins: (2) rivers transport eroded rrt:rials. se\\rsL- plant eftluents. and urban \\'astes to the occ-an:.r, I r insecr: and aninrals release urint-'. teces. and other \\,astcs tLr e' ironr'' rnr. t\ rhe) nriqrate around the Eanh. When plants and i::;.]als dic rli!'r ntr)\ in! to a ne\\' en\.ironment. ther. deconrposg 1,:rr'ir specilrilr aJupted and coctoli'ed micru)rganirrns (and ihr::::--leic riciis I are ru'ic,a:c'd (.s<,c .st,t-tiort l9.lt. The teca.l-orai rt r.

r,:'diseasr' Iransrr.rission. often iniolving t-ocxJs and saters. and ll::,!lLli\iti()n rrl di\.tse\ in hospitals (nosoc-omial inlections)arr, ir

;', rnant er;.irrrnlc'. of pathctgcn ntoYctltenl br.t\\ een ecos\ stL,nE-,lh tirttr' :i par\r)n cough\ or sneezes. nricrr.xlrganisnts :.il:!) lr

l:inS trlnrpt,ned lo nL'\\ eco(\'stems-Hunt:rn' ll>o hoth delibcratelv and unintL'ntionallv nror.. lr

!:.,1)r!uni\iti. hcir"cen ditTerent ecosvstL.nts. Th.ir rrccur.. * h.r:.iirr,i.e' ..r:-.'aijricd t() en\ ironnlenls t() speed up nlicrobiall\ nldrricd alc!r"lidltion prrrcr,sses (.rc., biorcntcdiot irtn. st,t't ior: -l l.,,r 1t ltan li li:tni-11\s()ciatcil intc-ulurn ruch ur rtlii--oJritrlt. is a.].J,'..:.r:rrrl li\ l:-rcii\L- thc lirrntation ot nitrosen-trrins nodule. r

i:gttlt.tr's { \( r r:)/). 6-;l--i-t t. Onc' ttf thc rnost irnponant acciJ.:lir:1, )!lcs of ntitr0bial nto\ ernent is the usc- of mrdern transFx)n \h:;les such a: automobiles. trains. ships. and airplanes. These t,lrr rapidi-, rnore nticroorganisms lons distances.

TItr' tlite ol nricrcrrrganisms placed in environments *h.:a:r-\ n()rnie.li-\ d0 not ]iVe. or of microorcanisnts returned t0 th.i,':..'linai L-n\ ironrnents. is of theoretical and practical imponancIr.ihoge n: rhat arc normallt,associatcd rl.ith an animal host Iarsr,l:... c lost th. -; abi litr t() contpete ellectir elr. tirr nutrients u irh lt:a:, r,)rgaini\nt\ indiltcnous to other environntenls. Urr.rn mor inS .

L lc\\ en\irotrinent. the population of t.iable and culturahn;thogcns Sraduall-\. decreases. Horvever. more sensitive I iabilii-t\\!'\strent pr()ceL Jres. particularh rnolecular techniques. ind.i:ie th.rt noncultured nticroorganisnlsr as obsened uith l.ibr,,ii.,€'.r(,. Ir.//r 6.-it. ntal pla'r,critical roles in disease oc-currence_

Erc-n microorganisms recor,ered liom a particular enr.iroin::nt. aftergrouth in the laboraton on rich media. mav lose the

t-Terlrary-level consumers I +

I

co"

Ico.

T

&co.

E*CO, (Chemoheterotrophs

(Photoautotrophs,c h e moa u tot rop h s i

Figure 28.28 The \/ital Role of llicroorganisnrs inEcoslstenrs. Nlicroorgani.ms pla\ r ital roles in L-c,)\-\ \lcnr- ,r\prinjaD producers. deconlp!\\L-rs. and printarY consurncrs. C:.r-bon is fixed b1'the printary prtrducers. includins 111ig1-1r1r1'g111i.11..

ri hich use light or chemicall-r bound energ\,. Chentol.r.-tcrotroFhi.hacteria and fungi ser\,e as the main decomposers of organic ni:t-ter. nlakin_s minerals again arailable lbr use b1,the prirnar1,p. ,-

ducers. Ciliates and flasellates. intportant nticrobial prim:.nconsurner\. t'eed on the bacter-ia and fungi. recvclinc nutrient\ :spart of the microbial loop. Oreanic ntarrer (O\1).

aL()\\ stL'ni:. Ecosr stents hJi e hL't] n dctlned lrs 'e ontntunltic> ,,t'()rsairi\nrs and their pht:icai and chcrnicll e nr ironnrents th:rtt-unction as sclt-rc'gulatin_s units." Titcsc- sell'-r'egr-rlating biol,,S:-c:rl units rcspond to environnt.-ntel citangr.s br ntodifr inc rit.-irstruciurL- and lunclion.

\licroortanisms in ecosi \lenr\ clln hlr c tu t, crrDrf le nrtiltri-\rolr-i'(l)the sr.nthesis of ncu or-ulinic rrtittcr ll.on.r CO. anci orr::inor!lnic conrpounds r.lurin!: prinrar-r production urtrl rIi.:.---r)ltjp()\iiil)ir ,r1'thi: accurtiulllttil ortuitic rl)lili!'1. Titt Sc;ttrlri 1".,:,-

trolrslriPr trclriu'cn the prinran pr()drrcrrs tha[ \\nthc.t1c ()r!i.::]t-iI[rttai-. tliu hL'tcr()trophic dc'composcrs. antl tltc, c.rlt:ut]]cr'\ lrrc ;,-luslnrlc't! in figure 28.2{1. \1i;;-.r(rl-!liili.r'n: ol'tliliclcni l} f --\ !, ..-

lribtitc to cae h ot'lhesc cornllcllclttlir\ rclation:hip:.In tcrrcstri:rl cnr ironnrer.i:. the f rirlarr f r-\)i-iucers arc LlsLli.rir.r

rascular plants. In 1ic:h*eier an(l riiarinc environntents. th.-cr anrrbacteria and alsae (.rt,1 .t t./ror ) 1 .-l rutr! i.lttrltta r l5 i plar .,

:ilnilar rtrlc. The ntajor ene ru-r :()urcc rit'i\ ing pritnlrrr protiuctii.t,i. lirhi in hrrth habitats althouch in hr tlrotlterntal and itvtiro.-r.:hr,rt sccp lrcas. chemotrophi. ecos-\ rtenl\ oce ur.

-l'he highe r con-

surnt:rs. including hunian.. arc eiicn.roirelerotroph:. l-hc-;d(,il\UilrL.r\ ile pcnd on the "liii \Ll1)l)()t-i \\ stcnts" ltror ideri br ,,:,!:lrn irrn: thlit accutnulate lnij iccontP( j\d ()l g:.iltir lnittter.

\liertxrrsanisnls thus uan out nt.1n\ intn0rtan[ l'Lrnction: r.thcr irrtcnrct in ecosr stenl\. in.luding.

l. C',rrrtrihr.rting to the lirrnr;'-r,,n oI o19i111i1. rnuttcr through 1th,,-losvnthctic and chemos\ nihctic f r()ccsses.

l. [)ecornposing organic ntaiie r. often u ith the rclease ol in,,r-gunic cornpounds (e.q.. CO.. NH. . C-llr. H.) in mineralizr-lion processes.

28.29

abilitl' to sun.ive s hen placed back in their original environnlent'-l-hc caurr' Ilta\ be phvsical or phrsiolo-tical' Frorn a phlsical,tiutdp{rint thc nricroorganisnts nraY tlnd thenrselves outside their

irrr)tcclcd phl sic;1 nicllc. $ hcre thc-r' 6i1n fs gonsumed b\ proto-

ztra and other predator,s. On tl.re'other hand. atier grosth in rich

lrboratr)r! llleclia. theY nlal have lost the abilitl'to conlpete phvs-

rologicallr ri ith the nalive populations.

1. Define the following terms: ecosystem, primary production,

decomposer.

2. List important functions of higher consumers in natural envi-

ronments.

3. What are the important functions of microorganisms in

ecosystems?4. Hor.r can microorganisms move between different ecosystems?

5. Why might microorganisms isolated from soil or water, after

being gror,vn in the laboratory lose the ability to survive in the

environment from which they were taken?

Stress and Ecosystems

\licroorganisnt: lunclion in ecosl'stems that develop under a

,, ;clt- r' 'rge r.. enrironmental conditions. These have Yaried pHs.

k-n1per:]tures. pre\surcs. salinin. $'ater availabilitv. and ionizing

r:rdiatitrn as sumntariz.'ti in table 28.7' Such stress factors have

r:rajor etlects on microhial populations and communities- and can

create xn extreme enlironment. as shox'n in figure 28.29. In

ihcse cases high salt concentrations. extreme temperature. and

acitiic condition. hare altected the microbial cornmunities. The

nucroorganisnt: ihat \un i\.e in such environments are described

rr\ e\trenlophiles. and <uch eltrente environments are usuallr

;onrirL'reJ to hr\i .ircreascd microbial dirersitl' as judged br.r1.-' 111i.;,ri,;g!nir:it\ 'iijitt can hc cultured. \\'ith the increased use

, ,t' lnrrlciular d.i.'i1t,!r) techniques. horvever. it appean that there

i. suryi-i'lng dircr.itr iini(rn,ll thc microorganisms that cannot he

.,.rilureJ l-i(rrll til1.-J c\i:'arllL'cnrironmenls. Further *Ork lo es-

i:rb'lish rtilrtion.h:|: hc'triccn thc n'ricroorcanisms that can be ob-

.cr\ L-ri l:i rri dctc;t -'.i hr '.hc-sc- ulolL-cular techniques and culturable

nicr()L)r::anisnrs ii iil bc required in the tuture. Thc irr:-.:--':,'.1.ii .:''. ,lt:t.. : _t -_ t- . ':: ::' I l\ ].

\1ai:r rliicr,,r'iel gcnera hare specilic rt'quirements ttrr sur-

'. iral ani t'uncti(,xinS in such sct-callc-d extreme environrncntt'

Fi)r !'\rintple. e high sodiittl-t ion concentration is required to

;irilinrrin nternl,.rune intcgritl in ntanv halophilic bacteria. Includ-

ins nr.nrh!-rs of lhc gcnus Httlrtbacleriurrl. Halobacteria require a

.()Lliur'il iL)n Cooccr,il-lrtitrn ol-at ieast l.-5 i\{. and about -3 to J ll tor

llptinlunl gro\\th. i:,,:'; r- iLI.|i::.: rli'. llirll -l-11 -i'r'

The bacteria li,unu tn deep-sca environment-s have dill-erent pres-

\urr' requi.cmens. delo-ndinq on the depth from u'hich thel' are re-

coveretl. Thesc bactcris u.rfl wk- described as baro- or piezotolerant

lracteria (cro*th trorrt approximatell' I to 5(X) atm). moderatel-r

barophilic bacteria igro* th optimunl -5.(X)O meters. arnd still able to

gro\\' at I atm). and extreme barophilic bacteria. u hich rr'quire ap-

proximarclr' -100 atnt or higher fbr grou'th (see r-lrupter 29t.

Characteristics of Extremenisms Grow

Enr irtnrnentalConditions

The Physical Environment 6(,5

IlicrooryanismsObsenedStr€ss

Hish temperature 1l I 'C Geogennra baros-siiPtrulobus fitmariiIt ethanoptnrs kand I eriPtrciictirun abyssiPlrocrrcls ab,vssi

ThennusSullolobusThennothrit Ihiopant

P s t <:hn.wnnas ingrdani iChlumy,lontottasHolobccteriumHakroccus

SaccharcmycesThiobacillusPicmphilus oshimaeFermplasma acidanwusBacillus

TorulopsisCandida

CyanidiwnS u$olob*r ac idocalda rum

C o I *' e ll ia hadal i e ns is

f) e intrtx'c trs rad k;du ra rc

L0\\ tcntl!-rJlilrc-

O5molic str!'!i

Acidic pH

Basic pH

Lo\r'u'ateravailabilitl

Temperatureand lou pH

Pr!-ssu rc

Radiation

I lO-l 13"C, deepmarine irenches

67-lOl'C, marine basins85'C. hot springs

7-5'C. sulfur hor springs

* I I'C. antarctic ice

l3*15? NaCl25% NaCl

pH 3.0 or lou'er

pH 0.5pH 0.0

pH 10.0 or above

tu = 0.6-0.65

85'C. pH 1.0

50O_1,03,s arm

I.5 miilion rads

Intriguir',r chrnge . irt hl:ic phl sitllogical proce\scs occur in

nricrtxrrgani.;rs i'r.tr.tciir'tiinL uniie r e \trettte acidic or alkaline con-

dititrn:. Thc.r lciiiof ir :i ii rnd rlkalophi I ic micrcxrrganisms have

nllrrkcdlr di::'.,r'tlrt nr,,l.l-lrn. in rnurrrtuining a m(lre neutral intemal

pH and clrrir',i,r'.lr!)li. t'itl'C:.ar t:it t'ltriplc'r 91. Obligatell' aci-

El.rphiiic illi-:1x)i!lriii.rlr\ air:l lrt)\\ l: I pH til' j.00r louer. and ntl-

.ior pll tir ti r'rt;lLe 5 e i.il'i t t l.i itl rr cr'n tlrc irlteritrr irlrd c-t teior- of the

cell. The rc :riidophil.'. inclirJ.' ntcttrher. ot the genera Tltiobocil'Itt.r..Srr1ii,ir,,;'.'.. ittlti 71,r '7",'"i.;'r'i1;- lllc hii:herrClatir.'intcrnal pH

i. n-iaintitir-i:.i i.r l trcl ',r.ii\,,.rlLi ii-itll\ir)rltlir)ll of proltlns, Thi: nlal()ccur il: ilta r-.-\ti]l ot i.ilitli.rr ;ttinthi-ltnt lipids. h"drogen ion rt--nioral dr,irir-,: reductiott oi Lr\rgr'tt l(r $ltler. or thc PH-dePcndentchiiracterislic. of nrcnrhrane-bound enzvrnes.

.\ n arch.r;'rl i ron-,., r i d i z-i n-r ac itloph i le. f-e r n' p l u s fittt u c' i tlu r -

Dt.iltus. ctii"r:'ic rtl ,!ii,,,itlr at pll (). hir. bcen isolatcd l'ronr a sul-

iltlc orc bi,.', in C:.;r1,,rnia- This unique pr(rciLn()te. capable ofmassire suri:.1,c gr,,.i lit in tlou itl! rlltdr. in the suhsurlace (lig-ure 28.30r. t1,\\!r\\U- l, .insic pcriphcral cvtopla.ttric nlenlhrane

and lrtl cell "r

riil.The ertir ttie ll krr i, rphi I ic ttticroorganirtll\ srL)\\' al pH values

ot'10.0 antl highcr rilLi tlrLl\t tttrtilltuin a Ilct in\\ard translocationof protons. The :.' r,hiii:ute alkalophiles cannot -rrou belou a pH

of 8.5 and arL- ()ftcn nl!'nrher\ o1'the senus BucilLus; lvlicrccrsccus

and Etiqut,ltuctcrittnt rcprescnlati\es have also been reponed.

Sonre photi>.r nthctic cvanobacteria also have similar character-

istics. lncrerscd intcrnrl prolon concentration\ nlal'be nlain-tained by' nr.an\ oi'coordinatecl h1'drogen and sr-diurn ion fluxes.

il;':'

Environments in which

6(}6 Ci.rapter 28 Microorganism lnteractions and Microbial Ecology

Figure 28.29 \licrurrganisms Grou'ing in Ertreme

[,nr ir(lrlllrt'nts. \'l11ll\ I]liar(i('rSrni]lil: l!il- c\p..iilllv suited to

sLrr\ r\. il a\llJirlc !'n\ir()nlnent\. tai Seltc'rns lurne<l red b1

lxllrpl,i,:. .,1!l:'l li,.i helohect.'rilr. tbr:\ h()t sprins ctllored green

artrj bli:.- f , 1... 1111i:i..1.1ci-iul grrrrith. 1c)A source o1'acid draina-ue

f'ri,lt.i tr:t,iir.. !lttt,3.i;clrpt. Thc.tiii and gliterhare tr-rrned red due

ro tit!- ir:.-..jl.c .,i-i.ia.ipilrrtarl iro:] tlridc's causcd h1 thr' actir it\'

crl' hri.t': rr rr rrtch li. "l' I t i t t l' ti c i I I u s'

Figure 28.30 \Iassive Grouth of the Ertreme Acidophile

L.irroplasma in a California \Iine. Slime strc-anters .t'Fc,r.rr-

pltt.srritt ttt'idttrtntttttrs' an archaean. uhich have dr'reloped *'ithin

prriti" sedinrents at and near pH 0. This unique procarl'ote has a

.ingle plasnta membrane and no cell uall'

28.30

28 31

\

-l-here is Srdat interest in the characteristics ol procar)'ote\ isolated

t-ronr tlit outilou Itrixinu regiotrs abor e cleep h1'drothe'rmal \ cnts thltrelease \\ater at l-i0 tcl 350'C. This is becar'rsc thesL- procar\otes can

-sro\\'irt t!'trlperatures as high as l2l'C. The probicnl' itl rrL)\\ing

tirc'se nricroorsanisnrs. often archaea. arc lbrnlidlirlc For eranrple. ttr

sr()\\'s()nle of them. it rvill be nL'c!-ssllr\ to usc special culturing

charnbcr. and otlier specialized eqtripnlent to ilrlintaitr seter ilt the

liquid state at these high ternperatures.

strcil nlieroorganisms' ternled hr perthcrlll(ri-hilL-s' s ittr optinlunt

-Lrtrrvth tr'rrtperatures of 80 C or lfrprg 1'tcc pit' 121-25t' cl)llti()nt

uniqu.' challeltges in nutrient accluisition. nletlrhtliisr-n- nucieic acid

replication. and grotth. \lanl ofthesc are anaeroLrcs that dcpend on

Microbial Ecology and lts Methods: An Overview 607

nisms and Modern

elemental sulfur as an oxidant and rc'duce it ttt sullldr'. Enzrrtte >1:.t-

bility is critical. Sonte DNA pohtrterases are irlh!'rcn'ril stlt'I. at

i40'C. whereas man)'othcr enz)'ntes are:tabilizc-tl irt riro rrith

unique thermoprotectants. \\'hen rhese enzllltes are :cperatcri ironltheir protectant. they lose their unique thernrostahilin.

These enzl-mes may have inrportant applications in Irttthrittc pro-

duction. metal leachin-l and recoverr'. and 1nr ltsc itt inttttobili,'r'u cn-

z) me s)'stems. In addition. the possibilin of sc'lcctir e \idrc('(ll.'Iliicillmodification of compounds normallY not in solulitttl 11 l,[r cr li'l:l]re r-

atures ma) prcr'ide ne\\' routes for directed clretrticai sr ntlicsc.. This

is an exciting and expanding area of the modcnl hioloric:rl \cicir;er toqhich microbiologists can make signilicant c!)rltrihuti\!1r..

fl.tc

Obsen ation,s of nricrobial sro\\'th at tell-l;-,'rature s approach-

ing tll'C in therrnal vL'nt areas. orof h] pertlierlnophiles (Tech'

niqucs & Applications 28.3; .sec ulstt ,llitntbiul Dii.r'.rirl d[:, ()l,t!\ /- / r. indica, ' tl' lt ihit 31g-;i u ili ci;nl]nr' ' ttr be e ttnilellelcl lirr irtresfigiition. Ftlr.trtlle Stluie.:tUl il':icrot't'l-riii'llli- iltt

e \trcnrc cnr ironnrent llla\ n()t be "tr.tt'tttlc" lrLrt rcquircJ and

c\ L'n. pcrhlf \. ideal. fi::- ' . ' , ':' l- -- I

1. What stress factors can create extreme envii'onments?

2. Deflne extremophile and discuss an example of adaptaiion to

stress resulting from \/ater availability, pressure, or pH.

3. !!hy are molecular techniques possibly changing our view o{

these environments?

4. Y/hat is unique aboul Ferraplasna acidair;l2l'us?

MICROBIAL ECOLOGY AND ITSMETHODS: AN OVERVIEW

As rr ith s() nlilrl\ aress oi science. ltn lltl.to.t be$ ildc'ring a\sort-

nrcni ()1' nrL-lh()d\ i: ar ailablc t() thc nlicrobiril ccol. ::i:t. \\'e rr illC61:itlc'f plinterilr ntcthod: f<lr c.ratllining rl,lc16lrilLl crrlllllltloi-tic. as contpicr asrentblag€:.

E x a nr i n at i o n of l"'"4 ic ro i:i a I Cc m n-r u t', i'; i es

as Conririex Assemb!ages-l-he :tudr ot'nricrrrbial cLrntrttultilic: ll\ c()llllllc\ assetlh.*ges has

['r.'cn a lirniilLlnL'ntal l'ocus o1-nticrohial cc()]o!\ in rr hich tlticro-

seopic. cultr-rral. phl sical. che nlie al. arltl particr'rlarlr rnol' uiar

tcchniqucs plar inrportant roles. ln tllltt'lr \tL1(iic\. bulk nucleic

acids ar-c raco\ e rL-d b1 dire ct extractioll tcchrlrclr'rcs. Horr cver. itha: bc'cn f ound that rhe DNAobtainecl can \irr\ dcpending on the

nlethod employed. This makes it difflcult to stat!' rr ith cenaintrthat the microbial contiltunitY has specilic citara;i.'r-istic. ba:cdon the use of a single DNA ertraction pr().!'rlLtre -\ .eetrllti Pt-ob-lem. espc-ciallr rr ith ntuds and soils. is that trl'tc h.f irr) I..n\)\\ lcdqtr-

of the source of the bulk-extracted DN.{. Tht l)\.i lceor:rr-r1 h1

this approach rttav not elen br' r.ler-irctl 1l-oiil l,r;'.* {,rJ-rlli\:'ll\.

Third. the D\A mar hatc tre.-n rccoreretl i'r.,i;l ::,ri,litililiirtrlilpropa:ules such as fun-eal tlr bactcrial \p()i-.':. i'; ,rli1c: :i:tinsstructures. Thus the senera idc-ntitled br :trcli rir,rlcd D\.-\ li-braries nlay haye minimal rele\.itttcL- ttr the tttict-,,hIrI cot:t:tiLtttitr

actuall)' fun.-tioning in the particular .'ltr iirrrlrl:rilt. \1 rl'': aJ-

vances are no\\' being madc in culturiiii: f t.cr ir'.t.lr irttii,liur.'tlmicroorgani s nrs.

h is important to note th:rl all tttcthorl> lt.rit i:: lcict:i lt;ltilr-tions: a critical chalh-'nge is tr.r rr'cogttizr tilc.!- lirr.,::iii\1i:' .rn!i li'understand ll'hat intirrmation a panicullu ttttiil,'i ,iilI ir;:J rriilnotl pnrvide. Generallr. it is bc:t I() Ll\L- rll(tl. lil.-', .'il. Ill.':il()i t,'

obtain conrPlcrncnlan inl'ornlatir)11 tltl di1'1cl'ri'l ..-l.r'i. , i .r ilrlcrobial communitr'. Second. sotlte lrL'th()rls itc 5.-li:r rLliir'- io tlltstudl of one tvpe ot'enl irtlnt:rent thitn irll()1har. []ir: a\i:llilia. L1L'-

cause \\'aters have feuer interf'ering inc-rt particlr'> ti'titl.t rtiud: or

soils- it is easier to rietr nliglqrhcs ()r l\) c\li.:,'i cc-ll,:l;.,1 cotl-

stituents fr-rr use in tnolecttlar sttrdies. Finallr.lr;1' .111r111.1 ;..g ilirproaches suilable lirr thu- studr of all nticrollilri -' '1.5('rl:'li. ()l rr

habitat (bacteria. archuca. and eucarroles). Oii';: ".

r\('. , I.. lll.i\miss critical relationships that arisc'bccltttrr- ()l irrl'irl.:ri'n\ lr.-nleen dit'lercnt gr()up:.

The methods used ttl charactcrizc c()lllPlL-\ ;l'rliIrrlr;r:r ctrtti'r-nunities can be directed ttt*'ard sereral cott,r:,..'tilr irJtLlrt.:numbers and n'pes ol nlicrtlbcs. nricrobial c()lllr'.:rllit\ -iruLtulcand iunction. microbial r iabilitv and stress sctt\ili\ Iir. r:iiirobialactivitv at various time scalc-s and levels ot rest,i,-liit,t't. an.i ntcch-

ani-sms of conrnrunication bct\\'een nticrobcs. -l-1ll.r li.ic;t' u illnou be briet)y discussed.

6()A Chapter 28 Microorganism lnteractions and Microbial Ecology

Numbers and Types of Microbes

A varien' of standarclized grtluth nlr'tlia it ttscti irr ,lir.-ct r ilihlr-

COUnt pfOCedufeS. *hiCh arC bltSCd ()t) C()i(rl1\ l'tlt tltlrlioll Lttltl e tltt-

nleration. These Irtethrlds are ilihct.'tttlr hilt:eLi. rit ltli ltll tlli-crobes rvill be able to gro$ under a pltrlicriiar.r-t ot er,rlrlition:.

If it is necessarl' to isolate spccit'ic gl'()tlp\ tri ttlicttrlrc:. ()r t() ilt-

tempt to search tbr organisn-rs $ ith ne$' clilibrlitir'- crtrie hntcnt

techniques (see pp. 102-5\ .lls() carl hc u:cd. 1-hc:c lcciirtitlLLct

are based on expansion oi'thc- tlricrocnvirortrtlc'llt tr) llll\\\\ llllt\-sive grou'th of an rtr-tanism forlllerl\ re\tri.tc(i {() :r \lllLtll L-'()-

logical niche. This approach still is r iiluebl.' itr 't'.ttlics r'i'

microbial ecolo_sl and pla\ s a ccntrlrl rolc in t'intiinL ltc\\ lnrl url-

described microbes. It also call he tl:t--ti itt tll,'.1 "11rhl1irl1' ttLttlllrc;

approaches to estintate populatirrns 01 s1.gr'lll. irllr.iLrlolie rlsroups in an environment.

\\:ith enrichrrlent techniqucs. hrrr,rcr.cr- tllicr,"'lL;,tli'llr\ lll[l'ibe able to gro$ under the test c()ndititrll: til'il ill!' ,''1'j. [f o trill-t'l

microbes can be obsen'ed in enlironllletll'. i'ili crtrichrtlcttt ap-

proaches and other cultural techniquc's do ltot $ork-tl,' Sro$thcan be obsen'ed. There are tu'o alternatire L'-\plallalion:: tl-ie ob-

sen'ed organisms truly are nonliable. or thc ri-cht conditiotls fttr

their grou'th in the lab halen't been crcalcri. l-his has lci.l ttr thc d.'-

scription of such potentialh' r'iable nlicrr'ht' a. bcins "li\)ncilltLlr-

able" (see p. 129). With et'fon. there har r- i'':cn starllrrrs \u...\\ciin this area. It tcxlk orer 70 rcars t() lli.lrt ().il llir\\ I{r,{rtr\\F ra nkia. the plant root-associ ated ni tro::c r -ll r i tr -s

ir' i i tl "

rtt r eclq'

The basic assumption should be that sitll tllirre eil(rr1. rt "rill t'epossible to Sro\\ these uncoopcretirr' 111l;; r;-;.jr1i'11'1-

Another critical problem in Srorr.ing rinti clilrrtcicrizirls nli-croor-ganisnls. particularl\ pr()tozrr3. alLrl. rinrl c-r l,t:"i-.r-'lJri-r- i'that manl'of these "microtlrgani\m\ irra llctilail\ t:llcr,thiltl lt'-sembla3es. Of-ten cultures of thr'.c t\ pe : t 'l ttiicrt'itt. itra l1()t li\-enic: the,\' c:rn have surl'ace-associ;-t!c'ii iirl::ttlcnial li::":nars. iind

phagotrophs such as protozoa can "trlif" 1".i1g1'1'19;11:ir:li' \\ it':tlsuch microorganisms arc t-lnall\ rludictl it\ ii\!-nic ciiilurl.. tite i:morphological and phr siolor:iciil t'h;ir'rltcri't ic' irc.iue ntlrchanse duc to the lack oi qr()\\th l-ltcti,i--:r:lr.i vitliirrirl' 1t'rlll.r-l)

pror ided bl the cornmensal orglrniinls.It is one thing ttl proride th!- Ilutriil)t\ -,11j a1r-r""til llt.-.j:e th:lt e

recalcitrant microbe require s. C)tten. tire phl:ical cnr irrrnnlcttt ai:t'mUSt be tailor made__that is. it rlur he na-..\l.rn l{1 lliriil- titr. lrc-

tual phlsical. ofien protectirc. lichc titul . t:ircr.b,.'tlrt. it.t tt;.t1ltrl.

Microbial Community Strltcture anc Ccrrstiiuents

To assess microhial c()nllllLll)it) \tl'LlL trli,' Illr,lLii dilli-rillr\i\ i'given to thc use ol-direct olrscrr litlt,tl of i,.':lllilr ;;ri.r,'hial e ott-,-

munities in nature. J-his can bc crir.'ied ()ui irr 'itu Lt'irlS iltlrtlcrscti

slides or electron niicroscope r:rid-.. placetl lll 11 l"rirtlrlrl rrl illtcr-est and then recoYered latt'r ftlr oLr\L-l-\'ati()li' Slilllf il' takctl l'rtltrl

an environment also are exantined in rhc llrbor-att'r) using clessi-

cal cellular stains. fluorescent stains. or 1-luorcscctlt tnolccullrprobes (see p.622).

B1' combining direct obserr aticrnai and rllt,lce ular tc-chtlic1Lte..

microorganisms and their ph1'sical rclatir,rr.hips can he studiccl.

28..

Figure 28.31 The Use of Differential Nlolecular ProbesStudl' \Iicrobial Community Characteristics. In this stur

speciallv designed rnolecular probes rvere used tc'r studv t

ph1'sical relationships bet*'een trvo archeans: a larger archa,

host. a menrberof the genus /.qni{'()r'r'tt.s (qrrrrt). ancl a nanosiz( -- ;100 nrn ) h1 perthermop,rili; .-;n,b,.tn i fl rrrlr J,',' o I t oii t'(,. J L .

Lquitons trcd). Bar : I pm.

as shorvn tbr the N' unoarclrua tun e qu il u tt s'-lgrticoc.r'tt.s cocultL

ttigure 28.31). Using specific molecular probr''. rt uttiquechaean. -l(X) nm in diameter. u'as tbund grosing on a largc-r'

chaean. 1.(rrlr'rrccrt.s. in a spccial relationship. i\ttrrtttttr<'lttt'Lrttt )

the smallcst archaean gL'norne tbr-rnd to date: onlr'0.-S nteSat,rl''fhus throush u:inq direct trbservaliot.t ilncl ntr)lL-cular Pitrhc'\\.-rs pi)\siblc to drr-untent thc lrlc-:tr le tll'thi: ullu:ual ;,trcil.'

:l'mbiont. apparentll' dependr'nt on its larser htlst for surr ir rLi

IIicrt'hial communities also can hc dcscrihed in tcrnt. ol ti'\li-ucturc an,l the nulrients cilntained in thr- cot-tltllLrnitr. .\qLr:

nricrtxrrganisnrs can be recolcrc'cl dirr'ctil rr:ins filtratit,rt:rolume. dr1 ueight. or chenticrl c(rnlcnt o1'the trtitro.rt-guttir

can then he nrea*sured. If it is not possible to re.()\ er the cells. e

hon. nilrirgctt. phclsphclru:. ()r lln ()l !ltl'liu c()n\tittlent ()l- tha c!(\uch .r. lipids or c-rgosterol) can be rlet.'rn-rinccl. This s ill sitringlc-iuluc'estimate of thr-- nricrobial corttntunitl. Such sirt;relue cherriical measuremenls cith.'r tttar be uscd dircctl\' or

pfe::eri a: rnicrobial biontass. Such inf,.lrrlllli(rtl is neL-Lle(1

cstlhl irh Rcdtleld ratitts ( -set' 7r. (r 1 9 ) o1' the nticrt,bial hi r,tttass.

pccialll in aquatic environments.Srngle-r'alue estimates of nricrohill constitucnls or biottl

lulthough valuable. provide no infornration ahout thr' ph1 sr

\true turc 0l microbes or of the nticrobiai comtttunitt'. For extplr-. in nature most filamentous I'ungi consist primarilr of cnr

h1 phae. A srnall amount of cvtoplasnr rloves \\ ithin the tubi

nctuork as the organism penetrates and exploits nes'substraSuch n.ricrobes. without distinct edqcs and boundaries. clo

I

Fi

il.i

\

2E,33

hale pledictable volunte-biomass ratios. arld iire clescribed as in-

rJctr'rrninate or nondiscrete microorganisms. With such rlli-

croorlartistlts. a sinsle-r'alue bionlass lllel-lsllr(] tllellt is of linlitcdvulue. as the organisrtts onlv can bc' described bl dirc-ct oh:err''a-

tion o1' their phl'sica1 structure.\'lolecular "fin-eerprinting" techniques are frequerltlv used

to characterize microbial colrlulunities- Bulk DNA. extracted

I'rom an eni'ironment. can be anall'zed directll or after the rrse

ol PCR anrplitication (see pp. 316-19). This provicles corllpar-

ative infbrnration: it also is possible to use the isolated DNA irtsequencing and probe-type investigations. Again. these ap-

proaches are limited by a lack of knou'ledge clf tl're DNA sotrrce-

and they' f ield no inforrnation on the physical structure of the

nr icrobial ccrnttrunitt'.

Stress and Viability of Microorganisms

I*nrlryxrrs are constantll' be i ng stres se d bl' pbffiksh'fuqsttand n' ilrie4*diar*d:nh s. Thus determini n-g whether thel' ter*m

dhltrfnotis3nJ@.Stress can be caused by the absence of m&ded'r+r*risn*q

leading to inlernal staryation stress, or it may be associated u'ith

qlIuas**ffifors. s uch as phlfig#rewfuonmoss€-l+fffi8e s - to x i c

gh*mixat s. or trytffi r{4}eEE s. Ir'1 i croo rga n i s m s e r e n {Ii,lJ-iil'leatcd bv a conthination ol intenral atld ertct-iiltl \tr.iscs.

S,,;::rtil:rc. :lirirt tcntpcralure changes. or chatlge: irl llll.iillbutler characteristics. can aff'ect microbes and the outcome of an

erperiment. Stress can be measured using c'I,*HMkt- For

exanrple. pli@ are prepared Vn'ith varf in-e

letels of a stressins agent such5[. $t*f:s*cd.or€imbms rvillno! sro\l rvell in the presence of the tm*iqa*d*. Recoven'

lionr stress can be evaluated because the recovering organism

gradualll' gro*'s better in the presence of the slressing asent.o can be nlade using

- rpx:cial ltain\ {.r('{'p. ?61 as iiiustrated in figure 28-32. irlicror i-

aL-ilitl measurenrents ibr the anall'sis of cell viabilitl' are briel11"

dcscrir^ud on page l?9.Th c s t u d 1 () l' s t{Spggbj&hili&Ic;g,ifl }p&*E#rran I 1r a n \ l re rr \

ol micrqp,!$,o+s,9lsg'. Even in the absence of visible gro"r.th' en

organisnr mal sho* 'li*:,$€tr.' u'hen directl1'obsen'ed' or rlhen

the microbe is grou'ing in its natural habitat. As an example. \/ib'ri{/ can cxist in a nominalll'}iebL*but nonculturable {VNC ) state:

it rnar not grou' in conventional laboratorl' rnedia. but it still can

srorl in a susccptible host. Thus it ma1' be difficult to ntonitor a

plth()::en's sun ilal in u'aters and in foods such as shelltlsh. even

tl-rotr::h it uill cause disease if it encounters an appr()priete sus-

ccptihle hort.

Microbial Activity and TL.'"roGtoef

.\Xhfl**!"tf,*i-:,ilX*lsaltl.ments can be rnade over vnrious tirne

intervals. ranging tiom the essentiall)' instantaneous responses ofsa nr p I cs c o n ta i n i n g ac r i ve nlisrp.hE'.Jo.*Jqeg.Js{+*gqqlqgigir I

p roc c s s - re I ated rne as u re tl e n t s.,\ fel eggglg;*St*gg!i&i{}' m e a-

s Ll re nre nts are descri&e,&t'tt#

e^^ At -d{g} h, ,,

Microbial icology and lts Methods: An Overview 609

Figure 28.32 Assessment of Microtrial Viability by Use ofDirect Staining. By using differential staining methods. it is pos-

sible to estimate the portion of cells in a given population that are. :able. In the Lr\rE/DE.A.D Boclight Bacterial Viability procedure.

nvo stains arL used: a n-rembrane-permeable green fluorescent. nu-

cleic acid stain- and propidium iodide (red) that penetrates onlycells rtith damrged nrernbranes. A Bifidobactenirrr culture is.

sho.' n he'r. Un- jured cells stain green. u'hile dead cells stain red.

Snfc#ic+saca{i*s. such as ni&ifiSe;ipn. denigifre*ion. and

U&i&Jsdusg{i[1 are studied by the use of di*eet'e}rerrricd'"1+ta-

slrrements. itltrqipqza lsee p1t. 345-55,98(ffi8) are now used

ro measure-j=Ij*Elgd;ii@ microbialcrr rnm u n i tie i. *4gi n. the results depend on{bes,aq#End qualityq&j&e#6b&ccids that are q&oxe"srjf qa.paei@k&{ff;@ei.gcommunill and i ts p|i$i$al*laatEi*mment. Stehle-i*dqe mea-

surements cd8air#*tale l#f*hsr"'acs,reswerogen. or other ele-nients hl*i&lwFoEex,x*4,4r*oe' ia@ee p- 668). Microbesgeneralll prelei the lightc'r of tn'o stable isoroJrs- as l:C o*'er '-tC.\\'hen a nricrok uses ca"lxu,d*ox.i@e- the

cells and nreta'l'olic prcxlucis otien have lou'er coacentrations ofthe heavv isortape than dcres the original substrate-

Y;Sm"U,tal"ggsxh"r.?i€s in complex systems also can be mea-

sureii directll. Ccl:nization of surl-aces can be obsen'ed using

rnicroscope slides or other materials. Chan-ees in microbial num-bers are follo*ed over time, and the frequencl'of dividin-e cells(FDC; is also used to estirnate production. This approach is espe-

cialll r'aluable in srudies of aquatic microorganisms. Finalll'. the

incorporation 1f 1adi'rlabc'lled cornponents such as th.vmidine (a

DNA constitu3nl) into nricrobial biomass provides informationabout grou,th r:rtes and ricrobial turnover-

*{i€fabial lnteiiacti S,,.,=q I

Simpll seeing microbes in ce,tair{thii*isa&seMips is or}pthe beginnin-e ofilhst€rl. The measurement of communicationrnolecules. such as aupi+duqsls.i.nxokre&i&€#@m#pfing ( s e e

l-? , hlllL, t^ L-C<r&

\

Figure 28.33 Recorerv ofSi@les from Compl@rrgl{ierorpapip.ukti$. By use

of-an inren.,l phut.-.ffiii microscope and a micromanipulator, a microorganism."Lls,-WJ**#direct molecular analysis.

(a) The bacterium to be isolated is placed belou the micromanipulator tip (diameter 5 to l0 pni) and a slight vacuum is drarvn. (b) The

desired single bacterium is drar,r,n up into the micropipette tube and is ready for molecular anal' ,'sis.

| f,

6to Chapter 28 Microorganism lnteractions and Microbial Ecology

(a) Suspension containing desired bacterium to be isolated from a mixlure

28.34

^(b) Desirec bacterium is laken up into the sterile micropipette tip

derstandins r!-\Jr(r:1s.\ o1' rlticroorganisms in compler environ-

ment\. anc ;.rnic'.rlurlr irt di'ea:c proces\es.

IUicrobial ect,losi.ts ll()\i u\e "reporter" microbes to char-

acterizc th; l.iri:i.-ri ;:li:rt'r'ttr irontncnl on thc scalc ol an indi-r idual br-icriit:lr ,i.r.i()trtLi I to i pnl r. This is dtlnc by

construcliirr utll: ',i ili: rep()rter genes. trttc'n based on green

l-luoresceni nr-()t.in rSI'pi that change their tluorescl'ncL' in re-

sFronse I(r .n\ irrrnnie ntal and ph1 siological alterations. Such"rep0rtL'r' l':ricr,.,bcs:lr: hcing used to n)L-asuIe orl'gcn al'ail-abilitl. UV i'e.iirLtion dirse. pollutant or tolic chernical etlects.and strer.. For c:.untf lc. \\ hL'n rllicrohe\ th3t contain a moisture

Stress rcP.:i.:- !rlte i:.,'.. 1.\\ a\ailJlrle $ater. thcre i: an in-

crease i n g i'!,-l-i-r.ed ll u.,rcsue itie.ln sunin.ian. the iiircct ,rbserr ation tlf nticroorSunirnls in

their natur.ii lrrr ironr':i.'n1.. j()nlbitlr'd u'ith carel'ullv sclected

cias:ical iullururl. e h.tn,rl:ri. lttd molr-cular techniques. is lead-

in-g to ne',i r itri : o1- h( '\\ It)iJr()()rganirnr. interact u ith each

clther. rr itn rrtitcr ()r{i-ifli:tll\ such a: plant-. and aninra}:. and

u ith their ebiotic L'n\ ironm.nt. Intportant neu' adl ance s con-

tinue to m;i.c ilticr,,'l.iul ccoirru\ one 0f the nto:t q'rcitinc arear

of modern .rtctrie .

1. Why are "classii" ,'rrcroscopic and physical methods still used

for the stucy o.| i-:icroorganisms when molecular techniques

are available?

2. What are optical t!"reezers and micromanipulators?

3. What iime scaies can be used when studyinq the activity of mi-

croorga n isms ?

4. What important advances have been made in microbial ecol-

ogy, based on th€ recovery of individual microbes from com-

plex environmenial samples, or by addition of microbes thatcontain reporter genes?

t'ru,od*.]y,,o-,\:'F.*'^,#&F-**EF*

t.rrtflrilt r^ ffrefrt %. .

1tp. i)9-J 1t. as u'ell as rtretabolic iniermediates and toric micro-

f 1r,l protir.rct: j" r olved in r arious s1'mbiotic interactions. prol'ides

kcr irilirirnltion 1ir unde rstandin-e hou and u'hv rnicrobial com-

r.rrunirics rtspirntl in spr-'citic uavs. The lreld has deveioped rap-

iillr. particLriuilr. in the :tud1 of positive and negirtive microbial

intcraction: u iih pl;.rnts and aninlals. This challenging area of mi-

crobial ecolo3) is discus-sc'd in chapters l9 and -i0'

R;:tove:y or Acidition of lndividual Microbes

Th': direct oF\er\atiort of microor-ganisms in their environments

i. e cntrai tr, ihe rriethttl,ti,-lg) used in an1' stud,v of microbial ecol-

ogr. In recent \ ea-r\. r aluable ne*' experimental approaches have

hecn derelt,ped to reco\cr and studf individual microorsanism-s

tionr an enr ironnienl.Such sir,'lc-cr'lI isolations can be carried out usinc optical

tlleezcrs ta laser roLem used to drag a nlicrtrbe asar tiom iisnei-chborst rnri br micromaniPulation. \\'ith a micromanipula-tor. a dcsired celi or cellular organelle is dra*n up into a mi-

cropipctte al-ter Jirect obsen'ation (figure 2833)- Once the

micrurbe is isolated. PCR amplification of the DNA from the in-

dir iclLrai celi r,r celi organelle makes available sequence data tbrrr:e in pl-rvlrrgcnetic analvsts (see chapter l9l- For exarnplt--. it hrs

b:cn po::ihle to e stahlish the ph1'logenetic relationship of a m1 -

crrplasnta rcc()\'erel liont the tlagellate Kttrugu bonitu bt micn.r-

munipuletion t figure 28.3J).

Clon;iclerrriLrn of r,,rcrobial ecologl on the scale of the indi-viclLral cc-ll ha: lc-d to important ecological insights. lt is no*' evi-

cient that thtre ii surpri ng hetero-geneitl' in u'hat have been

a,ssunrcd lo be homoqenous microbial populations. Cells of a ge-

neticall) uniiornt population do not have similar phenotlpic at-

tributes. the phenomenon of phenotl'pic or populationheterogeneitl'. This realization is increasin'lr importent in un-

fr^

$ et,,,,- *^+^

t

-:i.3 5Summary 61'l

Mycoplasma genitalium

Mycoplasma gallisepticum

Snaios'r.:,r:)lcqt': Ko ru ga hanita

0.10

Figure 2g.34 C,lrrbining \licr6ni:rnipulation for Isolation of'Single Cells or Organelles rtith the Poll'nre riise Chain Rt'action

1L) pnrla.d rbrp5rlo:cnr.tic analvsi. of the recovered m)'coplasmafollou,in.s PCR ampliiiciition and sequencing of tile PCR prtrduct\.

nL'tic inli)rnrrtitrn. Flegclletc (Ft. capillarl rube (Ctl.

28.1 Foundations of Microbial Ecologya. $lost micnnrgani:rnr that can rc* t'bren cd in

comple r natural as:cnlhlaser und!'r a misro*r[Ecannot be Sro\\n 3t thr Prelenl time- \lolL-culu

techniqucs:r. nrakin:: it Srsribie to obain inlirr-

mation on thcx' uniultured nricrtxirganismr-

b. l{icrohial ctisnts' interaeti!n\ \\ Ith thclr II\ lng anll n()nll\ lng

environntcnts, Sr ntbio.t. i5 a [iirr()$ cr lcflIl that

means "t()g!'lhcr lilt'-'- the \tud\ of ttrganism-

orcanism intcrlcti()n\,

28.2 Microbial lnteractionsa. Svnrbiotic intcractit,ns 1 figure 2{l.l t include mutu-

alisnr ( nrutuallr bcne llcid md obligaton ). ctxr;rr-ation (mutuallr lt'netlcial- not obliqal()n ). and

commensalistic {prrxiuct of one orglmisnl can be

used b,:nellciallr b} antrther organisnlt. Pr':dation

Bacillus anthracis

Lact o b aci I I u s a c i do ph i I u s

inroires one organism {the predalitrr inge:trng,'

Iillrn; u lirscr (,r \l1rf,licI pra\. l.r:J'l:i'rlr :.:

l, 'nr jr.lcnll intdmJl InJlnlcnJn\'(' ( r' J'', r:1,:'l ' 'l

glmisnr or acellular inlectious a!tllt l. erJ Jnlan-

uli.m ta micrt bial pnrluct can ir:hibil rnotlle r

,'1131i.tn t. Cr)mfttiti,,n inr,'lre .,,r1.'ri'nt' e ,'r:.-

;etinr lirr space or a limiiinr: nttlrieiri. l-his eln11,,,1 1,' j,'tttinun(c (,1 ('nc ,rr'i.rlri'll ' ' , ' " ri'tcncc of both al louc-r p,rpulatiotts.

A crrnroniunl ir a ph1 rical a\\()airti\)il (ri ()r!rlrl-

isnrs that hare a mutuallr rcLnciicial rri;tii,nshiibarcd on positi\ c interacti,)n'.

\lutual ad'antage is central to Illlltl\ ()r!rlll\rllrtrSuni\rlt interactit'n.. Thctc inlt'r.,.:i, I ' \.,::

tre barcd on material tran\1cr\ rclrtcJ to encr-getic:. ccll-1o-cell corrtntunication. L'r irh) \i.i1l

proteclion. \\'ith sererll inrportant niutuaiistie

interactions. cherrolithorrophic mieroorqlin-

Mycoplasma nturis

ma to\vae

sma penetrans

Mycoplasma volis

Ureaplasma cati

Mycoplasma sp. str STOL

Mycoplasma sp. str BAWB

Mycoplasma sp. str BVK

Mycoplasma mobile

fulycoplasma pulmonis

Mycaplasma arginini

Mycoplasma bovoculi

Spiroplasma citri

Spiroplasma apis

M yco pl asm a p utref ac i e n s

Mycoplasma mycoides

Clostridium ra nosum

C I ost ri d i u m cel I u I o vo ra n s

isms play a critical role in making organic mat-

ter available for use bl an associ ted organism(e.g.. endos.vmbionts in Rifrra).

The rumen is an excellent example of a mutual-

istic interaction bet\1een e ruminant and its com-

plex microbial comnrunitl. ln this microtrial

community'- compier plant materiais a.re broken

do$n to simple organi; ttlnrpound. rhat can be

absorbed bl rhe animal. as uell :rr formings'aste gases such as nrethane that are released to

the environmenl (figure 2t1.6:.

Syntrophism simpll. means lrosth together. Itdoes noi require phl sical contact trut onll a ru-tually positive ransfer of materials. such as in-

terspecies hr drogc'n lranrfer.

Cooperative interactions are benetjcial f-or bo&.

organisms but are not obligaton tfigure 28"7t.

Important examples re marine animals. inclu{ie!

(b)(a)

'-

a!vi