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Prokaryotic and Eucaryotic

Cell Structures

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Morphology of Bacteria

A. Size- bacterial cells vary in size depending on the species,but most are approximately 0.5 to 1 um in diameter or

width

e.g. Staphylococci and streptococci (D=0.75 to 1.25 um)

cylindrical typhoid and dysentery bacteria (0.5 um to

1 um in width and 2 to 3 um in length)

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C. Arrangement

Examples:

a. Neisseria

b. Streptococcus species

which cause throat and

wound infection

c. Pediococcus

d. Staphylococcus

e. Sarcina

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Patterns of arrangement

Examples

a. Corynebacterium diphtheriae

b. Caulobacter

c. Streptobacillus

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Bacterial Cell Structure

1. Appendages flagella and pili

2. Surface Layers- capsule, cell wall and plasma

membranes, mesosomes3. Cytoplasm nuclear material, plasmids, ribosomes,

inclusions and chromatophores

4. Special structures

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Flagella (singular, flagellum)-thin, hairlike filaments extend from the cytoplasmic

membrane and through the cell wall

-propel bacteria through liquid sometimes as fast as100 um per second (= to 3000 body lengths/min)

-composed of three parts:

1. basal body

2. a short hooklike structure

3. a long helical filament

L ringP ringRod

S ringM ring

Gram-negative

(E. coli)

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Pseudomonas

Some pseudomonads

spirilla

Escherichia

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Periplasmic flagella-also known as axial filament

-special flagella that arise atthe cell poles and wind

around the cell body or

protoplasmic cylinder

beneath the outer mem-

brane of the cell wall

-responsible for the corkscrew-

like motility of the

spirochetes

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Chemotaxis

- the movement of bacteria in response to chemicals

in the environment

*attractant towards*repellant away

Polar flagellated bacteria (swim in back- and- forth fashion)

-reverse their direction by reversing the direction offlagellar rotation

Peritrichous flagellated bacteria swim in a very complicated

manner (the cell swims along a relatively straight

track called a run, when the flagellar motors reverse,the bundleof flagella flies apart and the cell tumbleswildly)

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http://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.mov

Movie of motile Rhodobacter spheroideswith fluorescent labelled-flagella

http://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.movhttp://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.movhttp://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.movhttp://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.movhttp://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.movhttp://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.movhttp://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.movhttp://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.movhttp://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.movhttp://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.movhttp://www.rowland.org/labs/bacteria/movies/rsphe_f_swim_1.mov

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Fimbriae and Pili

- found in gram-negative bacteria

-shorter, straighter and more numerous than

flagella

-not for motility

-are hollow like flagella but nonhelical

-thinner (3 to 10 nm in diam)

Fimbria

- belong to a class of proteins called lectins

which recognize and bind to specific sugar resi-dues in cell surface polysaccharides)

-frequently called adhesins (bacteria

possessing fimbriae have a tendency to adhere

to each other as well as to animal cells)

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N. gonorrhoeae and enterotoxigenic E.coli

-ability of certain organisms to cause

disease is associated with the possessionof fimbriae (loss of fimbriae is accompanied

by a loss of virulence)

Pilus or Pili-morphologically and chemically similar to

fimbriae

-involved in sexual reproduction of bacteria

(F pilus)*those with F pilus are donor cells and

those without it are recipient cells

(genetic materials are transferred during

bacterial conjugation)

Gl l

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Glycocalyx

- a layer of viscous material that surrounds

some bacterial cells

- special stains are used to show this layersuch as India ink (appears halo under a light

microscope)

-composed of polymers

a. Capsule if the glycocalyx is organizedinto a defined structure and is attached

firmly to the cell wall

b. Slime layer- if the glycocalyx is disorganized

and without any definite shape-attached loosely to the wall

-tends to be soluble in water

-medium becomes highly viscous

-produce stringiness in milk

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Capsules maybe:

1. Homopolysaccharide

-single kind of sugar-synthesis of glucan from sucrose by

Streptococcus mutans-to adherefirmly to smooth tooth

surfaces and cause dental caries orcavities (without the sticky glucan, the

microorganisms might be swept away

by flowing saliva)

2. Heteropolysaccharide-more than one kind of sugar

-capsule ofS. pneumoniae , type VI,consists of galactose, glucose &

rhamnose

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4. Capsules may prevent attachment and

lysis of cells by bacteriophages(viruses

that attack bacteria)5. Capsules protect pathogenic from being

engulfed by the white blood cells that

defend the mammalian body

6. Nuisance to industry (responsible for

accumulation of slime in manufacturing

equipment that can clog filters and coat

pipes affecting the quality of the finalproduct)

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The Cell Wall of Prokaryotes:

Peptidoglycan and RelatedMolecules

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Bacterial cell wall

- fundamental differences in ultrastructure ofthe cell wall are responsible for the reaction

(+ or -) of bacteria towards the Gram stain.

- In both types of cell,the cytoplasmicmembrane issurrounded and supported bya cell wall, which provides strength, rigidity

and shape. (prevents cell from expanding

and eventually bursting bec of water

uptake)

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-Usually essential for cells to grow and divide

(cells whose walls have been removed in thelaboratory are incapable of normal growth and

division)

-Account for as much as 10 to 40% of the dry

weight of the cell depending on the species

and the cultural conditions

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This material consists of strands ofalternating repeats ofN-acetylglucosamineandN-acetylmuramic acid, with the latter

cross-linked between strands by shortpeptides. Many sheets of peptidoglycan canbe present, depending on the organism.

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Each peptidoglycan repeating subunit iscomposed of four amino acids (L-alanine, D-alanine, D-glutamic acid, and either lysine ordiaminopimelic acid) and twoN-acetyl-glucose-like sugars

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peptidoglycan

Cytoplasmic

membrane

Outer membrane

peptidoglycan

Gram + Gram -

Cytoplasmic

membrane

Cell wallCell wall

15-80 nm

7-8 nm

7-8 nm

2-3 nm

Schematic cross sections of bacterial cell wall

Typical lipid-protein bilayer

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Peptidoglycans Alias murein or mucopeptide

Present in almost all bacteria (exceptions: wall-

less mycoplasmas; archaebacteria)

Unique to bacteria Essential function

(physical support of thecytoplasmic membrane)

Common architecture

but variations in

structural detail Ideal target forselective toxicitycontains3 kinds of

building blocks

1 2

3(tetrapeptide)

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http://upload.wikimedia.org/wikipedia/commons/6/6f/Gram-positive_cellwall-schematic.png

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Gram-positive

Relatively thick and featureless (electronmicroscope)

Major component (~50%) is peptidoglycan

No lipid and often no protein

Accessory polymers (teichoic acid and/orteichuronic acid) covalently linked toPeptidoglycan or to cell membrane

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2 major forms ofteichoic acid

1. polymers of ribitol phosphates

2. polymers of glycerol-aid in the transport of positive ions in

and out of cell

-aid in the storage of phosphorus

-highly antigenic(i.e. They will induce a

host to make specific antibodies); provide the

antigenic determinants used in the serological

identification of many groups and species ofgram-positive bacteria

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Lipopolysaccharides (LPSs)

-characteristic of gram negative bacteria(gram+ bacteria ,cell wall has no LPS)

-composed of 3 covalently linked

segments:

1. Lipid A - firmly embedded in themembrane

-extremelyimportant bec of itstoxicity to animals (also)

known as an endotoxinand can

act as a poison-causing fever,

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*the outer membrane is selectively permeable to

molecules on the basis of their electric charge

and molecular size

Porinsdiffusion channels formed by special proteins

where molecules pass

The general designation foroutermembraneproteinsincluding porins and receptors isOmp.

Removal of peptidoglycan layer in the presence of 10-20% sucrose , the cell

with CM is

called: spheroplast - Gram-negative bacteria

protoplast Gram-positive bacteria

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Cell Wall

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-it secretes extracellular hydrolytic

enzymes

- it ensures the segregation of nuclear matl

(DNA) to daughter cells during division

- it controls the transport of mostcompounds entering and leaving the cell

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Structure and Chemical Composition of CM

-approx 7.5 nm thick

-composed of phospholipid (20-30%) andproteins (50-70%)

-fluid-mosaic model

-semipermeable

-contains specific proteins called permeases

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diff sion and osmosis occ rs across the c toplasmic

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-diffusion and osmosis occurs across the cytoplasmic

membrane

Internal Cell Structures

-material contained wiithin the cytoplasmic membranemay be divided into:

1. the cytoplasmic area the fluid portion contg. dissol-

ved substances and particles such as ribosomes

2. nuclear material or nucleoidrich in the geneticmaterial DNA

Cytoplasmic area-consists of of about 80% water

-aside from water, NA, proteins, CHO, lipids, inorganicions, many low-mol weight cpds and particles w/

various functions

- no evidence that it has cytoskeleton unlike in

eukaryotes

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Cytoplasmic inclusions Where found Composition Function

Table 8. Some inclusions in bacterial cells.

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y p p

glycogenmany bacteria e.g. E.coli

polyglucosereserve carbon andenergy source

polybetahydroxyutyricacid (PHB)

many bacteria e.g.Pseudomonas

polymerized hydroxybutyrate

reserve carbon andenergy source

polyphosphate (volutingranules)

many bacteria e.g.Corynebacterium

linear or cyclicalpolymers of PO4

reserve phosphate;possibly a reserve ofhigh energy phosphate

sulfur globules

phototrophic purpleand green sulfurbacteria andlithotrophic colorlesssulfur bacteria

elemental sulfur

reserve of electrons(reducing source) inphototrophs; reserveenergy source inlithotrophs

gas vesiclesaquatic bacteriaespeciallycyanobacteria

protein hulls or shellsinflated with gases

buoyancy (floatation)in the vertical watercolumn

parasporal crystalsendospore-formingbacilli (genus Bacillus)

proteinunknown but toxic tocertain insects

magnetosomes certain aquatic bacteriamagnetite (iron oxide)Fe3O4

orienting andmigrating along geo-

magnetic field lines

carboxysomesmany autotrophicbacteria

enzymes forautotrophic CO2fixation

site of CO2 fixation

phycobilisomes cyanobacteria phycobiliproteinslight-harvestingpigments

chlorosomes Green bacterialipid and protein and

bacteriochlorophyll

light-harvesting

pigments and antennae

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c. Sulfur globules found in H2S-oxidizing bacteria

d. Volutin granules (metachromatic granules)-made of

polyphosphates

-reddish color when stained with methylene

blue

-appear round

Chromatophores-special membrane system found in certain

photosyhnthetic bacteria and cyanobacteria

-lacks chloroplasts

Nuclear area

-lacks nucleus

-nuclear matl in a bacterial cell occupies a position

near the center of the cell

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Figure 3. A variety of bacterial inclusions. a. PHB

granules; b. a parasporal BT crystal in the sporangium ofBacillus thuringiensis; c. carboxysomes inAnabaenaviriabilis, showing their polyhedral shape; d. sulfurglobules in the cytoplasm ofBeggiatoa.

seems to be attached to the mesosome cytoplasmic

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-seems to be attached to the mesosome-cytoplasmic

membrane system

-total nuclear material called the nucleoid consists of a

single, circular chromosome

Plasmids

-relatively small, circular pieces of double-stranded

DNAwhich exist separately from the bacterial

chromosome

- capable of autonomous replication and encode

for many auxiliary functions (antibiotic resistance) not

necessary for bacterial growth

-can be transferred from 1 bacterium to another thruconjugation or thru lab manipulation. (recombinant

DNA technology)

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Dormant Forms of Prokaryotic Microorganisms

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Dormant Forms of Prokaryotic Microorganisms

-some species of bacteria produce dormant forms

called: spores and cysts

-can survive unfavorable conditions such as dryingor heat

-resting forms (metabolically inactive) but in favora-

ble conditions they can germinate and become

metabolically active vegetative cells (grow andmultiply)

Spores

-only two genera of medical importance, Bacillusand

Clostridium have the ability to developed specialized struc-tures called endospore.

-form within the cell

-thick-walled, highly refractile and highly resistant to

environmental changes

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Gross Morphological Characteristics of

Eukaryotic Microorganisms

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Molds

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-multicellular organisms that look like filaments under low

magnification

-with high magnification, they look like tiny jungles-the body (thallus)

-consists of the mycelium (mycelia) and dormant

spores

-each mycelium is a mass of filaments called hyphae

Hypha

-about 5-10 um in width and is formed by joining to-

gether of many cells

-rigid walls of hyphae are made of chitins, celluloses

and glucans-maybe classified as

1. coenocyticdo not have septa(crosswalls bet the

cells that make up a long filament)

-contains many nuclei

2 septate have septa that divide the filaments into

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2. septate have septa that divide the filaments intodistinct cells containing nuclei

*there is a pore in each septum that allows cytoplasm andnuclei to migrate between cells

A hypha grows by elongation at its tip and each fragment

that contains nuclei is capable of growing into a new

organism

-some hyphae are embedded in solid media such asbread or soil to give the thallus support and nourishment

(rhizoids-specialized hyphae since they are rootlike)

Reproductive hyphae may grow upward into the air to disse-minate the spores they produce.

Vegetative hyphae- hyphae with no specialized division of

labor may simply grow along the surface of the substrate

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Germ tube

-a short, hyphalike

extension that soon

Grows into a thallus

th h h b i d i t l t t

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-other hyphae can become organized into large structures

to form the so called fleshy fungi, such as mushrooms,

puffballs, and bracket fungi.

Many fungi exhibit dimorphism (existing either in a unice-

llular, yeastlike form or in a filamentous form)

Present when the

organism is parasiteWhen the organism is a

saprophyte in its natural

habitat (such as soil) or onlab media incubated at rm T

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Morphology of Algae

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- are of many sizes and shapes

-species range from single microscopic cells to orgs

hundreds of feet long

-Singlecelled species may be:

1. spherical

2. rod-shaped

3. club-shaped

4. spindle-shaped-some maybe motile

-Multicellular

-some organized as filaments of cells attached end to end

-in some species these filaments intertwine into microscopicplantlike bodies

-occur in colonies, some of which are simple aggregations of

single cells, while others contain different cell types with

special functions

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-structurally and functionally more complex

th ti fl ll d ili

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than procaryotic flagella and cilia

-composed of thin, hairlike

microtubules: 9 + 2 arrangement (9 pairsof these tubules encircle a central pair )

-shaft formed by the microtubules

Is wrapped in a membrane

Differences bet eucaryotic and procaryo

-tic flagella1. movement is powered by the

hydrolysis of the chemical cpd

ATP for the eucaryotes while for

procaryotic flagella, the energy tomove it comes from the proton

motive force(the movement of

hydrogen ions across the CM)

2. Differ also in the way they move the cell

*eucaryotic flagellum-propels the cell by acting

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eucaryotic flagellum propels the cell by acting

like a whip, bending and twisting against the

liquid environment

*procaryotic flagellum-moves the cell by rotatinglike a corkscrew

Pseudopodia

-specialized structures as mode of locomotion by

some protozoans

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-a pseudopodium is a temporary projection of part of

th t l d t l i b hi h i d

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the cytoplasm and cytoplasmic membrane which is caused

by cytoplasmic streaming

-characteristics of amoebas

-maybe used to capture food particles

Cell Walls

-plants, algae and fungi have cell walls

-maintains the shape of cells and prevents them frombursting through osmotic pressure

-cell walls of plants, algae, and fungi differ from one

another and from bacterial cell walls in chemical

composition and physical structure-protozoa lack cell wall but some are surrounded by

a layer of shell-like matl (may fit tightly or form a

loose chamber in which the organism moves)

*scales or spines may be present

Table 4. Differences in the cell wall compositions of eucaryotes

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Organism Chem. composition

Plant Rigid; mainly polysaccharides

(cellulose and pectin)

Filamentous fungi Chitin and cellulose

Unicellular yeast Polysaccharide mannan (polymer of

the monosaccharide mannose)

algae Varying amounts of cellulose, other

polysaccharides and calcium

carbonate

-the walls of diatoms (algae)

*impregnated with silica making them thick & rigid

*surfaces often delicately sculptured with intricate

designs characterictic of the species

Cytoplasmic membrane

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-eucaryotes CM have sterols while that of

procaryotes generally does not

Cellular Organelles

-inside the the CM is the protoplasm

Protoplasm is divided into:

a. Karyoplasm- the material inside the nuclear

membrane

b. Cytoplasm- the material between the nuclear

membrane and CM.

-where organelles are found

-has cytoskeleton (network of microtubulesand proteins)

*provides shape and support

*serves as framework along which

organelles move thru the cytoplasm

Nucleus

- many protozoan have multiple nuclei thruout the

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many protozoan have multiple nuclei thruout the

greater part of their life cyle.

- in ciliated microorganisms, there are two nuclei:

1. macronucleus- large nucleus- controls metabolic activities, growth and

regeneration

2. micronucleus- small nucleus

- controls reproductive activities

Chloroplast

algae have another energy generating cytoplasmic

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- algae have another energy-generating cytoplasmic

organelle

-site of photosynthetic reactions(light is used to con-

vert energy for the cell)

-a cucumber-shaped body (2 to 3 um wide, 5 to 10 um

long) surrounded by a double membrane

Stroma- the interior

- where DNA(circular, like procaryotic DNA)codes for proteins on the chloroplast

ribosomes and for the enzymes needed

to use carbon dioxide from the air.

Thylakoids- stacks of disk-shaped or ribbonlike sacswhich contain the chlorophyll and caro-

tenoid pigments that function in photo-

synthesis

Grana- each stalk is called granum

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Dormant Forms of Eucaryotic Microorganisms

-some microorganisms can produced dormant forms

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some microorganisms can produced dormant forms

called spores and cyts that can withstand unfavorable

conditions

-both fungi and protozoa use such resting structuresfor protection and reproduction

-algae also form spores but their main function is for

reproduction. Algae do not form cyts.

Spores

-fungi produce both sexual and asexual spores

A. Sexual spores

-produced as a result of the fusion of two

specialized reproductive cells called gametes

into one fertilized cell.

-produced less frequently and in smaller numbers

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B. Asexual spores

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-does not involve the fusion of gametes

-each thallus can produce hundreds of thousands of

asexual spores, produced by aerial hyphae-purpose is to dessiminate the species, and are

specially structured for dispersion from the mother

thallus

*spores of aquatic fungi-may be motile in water

*spores of soil fungi-may have thick coats to

withstand drying or may be light enough

to travel on air currents

-usually white when 1st produced but they turn a cha-

racteristic color with age.-eg. Peniciliium notatum-colonies blue-green

Aspergillus niger- black

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Cysts

-resting forms produce by many protozoa

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resting forms produce by many protozoa

- 2 possible forms of protozoan cyts:

a. Protective cyst

b. Reproductive cyst

Trophozoites

-the vegetative forms of protozoa

-synthesize protective cysts that are resistant to drying,

lack of food, lack of oxygen, or acidity in the hostsstomach. (when conditions once again become favora-

rable, cysts form trophozoites that feed and grow.

Reproductive cyst- not induced by adverse environmental

conditions-often thin-walled and lack the resistance of protective

cysts

*parasitic species of protozoa often move from host to

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parasitic species of protozoa often move from host to

host as cysts(mode of transmission)

-form in the intestinal tract and are excreted in

feces which contaminate water and food ingested

by next host.

*CYST is the only way to survive outside the host.

e.g. Giardia lamblia -causative agent of diarrhea

and abdominal cramps in humans-transmitted to humans by cysts

in water supplies contaminated with feces

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THANK YOU for listening!