The Bacteria

Phylogenetic tree of the major lineagesof Bacteria based on 16S ribosomal RNASequence comparisons

The Purple Bacteria, also called Proteobacteria is the largest and most physiological diverse of all bacteria

Bacteria Purple and Green (Anoxygenic Phototrophic Bacteria) Cyanobacteria Prochlorophytes Chemolithotrophs: Nitrifying Bacteria Chemolithotrophs: Sulfur- and Iron-Oxidizing Bacteria Chemolithotrophs: Hydrogen-Oxidizing Bacteria Methanotrophs and Methylotrophs Sulfate and Sulfur-Reducing Bacteria Homoacetogenic Bacteria Budding and Appendaged (Prosthecate) Bacteria Spirilla Spirochetes Gliding Bacteria Sheathed Bacteria

Bacteria Pseudomonads Free-Living Aerobic Nitrogen-Fixing Bacteria Acetic Acid Bacteria Zymomonas and Chromobacterium Vibrio and Related Genera Facultatively Aerobic Gram-Negative Rods Neisseria and other Gram-Negative Cocci Rickettsias Clamydias Gram-Positive Bacteria: Cocci Lactic Acid Bacteria Endospore-Forming Gram-Positive Rods and Cocci Mycoplasmas High GC Gram-Positive Bacteria: “Actinomycetes” Coryneform Bacteria Propionic Acid Bacteria Mycobacteria Filamentoud Actinomycetes

Sulfate- and Sulfur-Reducing BacteriaRepresentative Sulfate-reducing and sulfur-reducing bacteria

Most are Delta Purple Bacteria

Desulfovibrio desulfuricans

Desulfonema limicola

Desulfobacter postgatei

Desulfobulbus propionicus

Desulfosarcina variabilis

Desulfuromonas acetoxidans

Sulfur-reducing bacteria

Sulfate-Reducing Bacteria Strict anaerobes, Divided into two broad physiological subgroups:

Genera in Group I (Desulfovibrio, Desulfomonas, Desulfotomaculum, Desulfobulbus)

• utilize lactate, pyruvate, ethanol, or certain fatty acids as carbon and energy sources, reducing sulfate to hydrogen sulfide

Genera in Group II (Desulfococcus, Desulfosarcina, Desulfonema, Desulfonema)

• specialize in the oxidation of fatty acids, particularly acetate, reducing sulfate to sulfide

Growth and reduction of sulfate by Desulfotomaculum in certain canned foods leads to a type of spoilage called sulfide stinker,

Habitants of anoxic aquatic and terrestrial environments

Sulfur-Reducing Bacteria

Able to reduce elemental sulfur to sulfideUnable to reduce sulfate to sulfideObligate anaerobesUtilize only sulfur as an electron acceptorAlso referred to as dissimilatory sulfur-reducin

g bacteriaMembers of the genus Desulfuromonas can gro

w anaerobically by coupling the oxidation of substrates such as acetate to ethanol to the reduction of elemental sulfur to hydrogen sulfide

Homoacetogenic Bacteria

Obligate anaerobesGram-positiveCO2 as a terminal electron acceptorAcetate as the sole product of anaerobic respirationAcetyl-CoA pathway convert CO2 to acetateTypical species: Acetobacterium woodii and Clostri

dium aceticum

Homoacetogenic Bacteria

Mechanism of autotrophy in homoacetogenic, sulfate-reducingand methanogenic bacteria

Reactions of the Acetyl-CoA Pathway

Budding and Appendaged (Prosthecate) BacteriaAsticcacaulis biprosthecum Ancalomicrobium adetum

Ancalochloris perfilievii

Stella

Budding and Appendaged (Prosthecate) Bacteria

Contain various kinds of cytoplasmic extrusions: Stalk Hyphae Appendages

These kinds of extrusions, which are smaller in diameter than mature cell, contain cytoplasma, and are bounded by the cell wall, are called prosthecae (singular prostheca)

Unequal cell growth, such as polar growth Majority is purple bacteria except Planctomyces and Pirella

which are unusual as their cell walls consist mainly of protein

Most are aquatic, many live attach to surfaces using prosthecae

A stalk is usually a prostheca except in Planctomyces

Budding and Appendaged (Prosthecate) Bacteria

Contrast between cell divisionin conventional bacteria and inbudding and stalked bacteria

Budding and Appendaged (Prosthecate) Bacteria

A Caulobacter rosette. The five cells are attached by their stalks (prosthecae)

Budding and Appendaged (Prosthecate) Bacteria

Stages in the Hyphomicrobium cell cycle

Budding and Appendaged (Prosthecate) BacteriaPhysiology and Ecology

Hyphomicrobium is a methylotrophic bacteria, widespread in freshwater, marine and terrestrial habitates.

Photomicrographs of cells ofHyphomicrobium

SpirillaSpirillum volutans

Spirillum volutans

Spirosoma linguale

Intestinal spirillum

Purple bacteriaGram-negativeThe genus Spirillum includes only S. volutansSpirillum volutans is a large bacteria, micro- aerobicAzospirillum lipoferum is anitrogen-fixing organism. It can form a loose symbioticrelationship with tropicalgrasses and grain cropsAquaspirillum magnetotacticum has magnetotaxis ability

Spirilla

Aquaspirillum magnetotacticum contains particles of Fe3O4 (magnetite) called magnetosomes arranged in a chain

Auqasirillum magnetotacticum

Spirilla: Bdellovibrio

Bdellovibrio bacteriovorus

Spirilla: Bdellovibrio

Preying on other bacteriaAttack and develop intraperiplasmicallyA wide variety of gram-negative bacteria

can be attacked by a single Bdellovibrio species

Gram-positive cells are not attackedObligate aerobe, purple bacteria (delta

group)

Spirilla: Bdellovibrio bacteriovorus

Developmental Cycle

Spirochetes Typically slender, flexuous, helical in shape, often rather long Axial fibrils or axial filaments are attached to the cell poles and

wrapped around the coiled protoplasmic cylinder. Both the axial fibrils and the protoplasmic cylinder are

surrounded by a three-layered membrane called the outer sheath or outer cell envelope

Spirochaeta stenostrepta

Spirochaeta plicatilis

Treponema pallidumcauses syphilis diseases

Spirochetes Arrangement of the protoplasmic cylinder, axial fibrils, and external sheath The manner in which the rotation of the rigid axial fibril can generate rotation.

Spirochaeta zuelzerae

Spirochetes: Classification Six genera (based on habitat, pathogenicity, and morphological, physiological characteristics):

Spirochaeta Cristispira Treponema (Host in human, causes sexual disease syphilis) Leptospira (L. Interrogans causes nephritis and jaundice) Leptonema Borrelia (B. recurrentis causes relapsing fever)

Cristispira

Spirochetes

Morphology of Treponema saccharophilum

Treponema saccharophilum

Gliding Bacteria No flagella but can move when in contact with surfaces Gram-negative, purple bacteria, some are Bacteroides-Flavobacterium Myxobacteria can form multicellular structures called fruiting bodies

Beggiatoa

Thioploca

Filamentou sulfur-oxidizing bacteria in a small stream

Sulfur-oxidizing bacteria

Gliding Bacteria: Leucothrix Chemoorganotrophic, requires both H2S and an organic compounds for growth Form gonidia under unfavorable conditions May aggregate to form rosette when gonidia have high concentration

Leucothrix mucor

Gliding Bacteria: Fruiting MyxobacteriaMyxococcus fulvus

Mellitangium erectum

Myxococcus stipitatus

Chondromyces crocatus

Stigmatella aurantiaca

Exhibit the mostcomplex behavioralpatterns and lifecycles of all knownprokaryotes

Gliding Bacteria: Fruiting Myxobacterium

Gliding myxobacteriumStigmatella aurantiaca

Have rather large chromosome sizeRely on lysis of other bacteria for nutritionsMyxospores are more resistant to drying, sonic vibration, UV and heat.Usually colored by carotenoid pigments

Gliding Bacteria

Gliding BacteriaMyxobacteria have distinct growth morphology

Myxococcus xanthus on agar

Myxococcus fulvusslime tracks on agar

Fruiting body of stigmatella aurantiaca

Gliding BacteriaFruiting body formation in Chondromyces crocatus

Early stage

Stalk formation

Three stages in head formation

Mature fruiting bodies

Sheathed Bacteria Filamentous organisms with a unique life cycle involving formation

of flagellated swarmer cells within a long tube or sheath Under unfavorable conditions, the swarmer cells move out and

become dispersed to new environments, leaving behind the empty sheath

Sphaerotilus natansActive growth stage

Swarmer cells leaving the sheath

Swarmer cell

Pseudomonads Purple bacteria (Proteobacteria), gram-negative Polar flagella, aerobic, grow at neutral pH mesophilically Chemoorganotrophic, never show a fermentative metabolism P. aeruginosa is opportunistic pathogen, some are plant pathogens

Pseudomonas have broad substrate utilization, some produce polyhydroxy-butyrate and some synthesize medium-chain-length polyhydroxyalkanoates,have been studied in our lab

The Entner-Doudoroff pathway,the major means of glucose catabolismin pseudomonads

Free-Living Aerobic Nitrogen-Fixing Bacteria Large, gram-negative, obligately aerobic rods, capable of fixing N2 nonsymbiotically Azotobacter has the highest respiratory rate of any living organism (purple bacteria) Azotobacter cells are very large, almost the size of yeasts, produce cysts

Vegatative cells of Azotobacter vinelandii

Cysts

Azotobacter cysts have low endogenous respiration and areresistant to desiccation, mechanical disintegration, andUV as well as ionizing radiationhowever, they are not especiallyheat-resistant

Free-Living Aerobic Nitrogen-Fixing BacteriaMajor genera: Azotobacter, Azomonas, Azospirillu

m and Beijerinckia, Derxia

Colonies of Beijerinckia species growing on a carbohydrate-containing medium

Derxia gummosa encased in slime

Free-Living Aerobic Nitrogen-Fixing Bacteria

Acid-tolerant, free-living N2-fixing Bacteria

Acid-tolerant, free-living N2-fixing bacteria

Beijerinckia indica

Derxia gummosa

PHB

Acetic Acid Bacteria Purple bacteria, gram-negative, aerobic, motile rods, tolerance to low pH Carry out incomplete oxidation of alcohols, leading to the accumulation of organic

acids as end products With ethanol as a substrate, acetic acid is produced

Acetobacter aceti on calcium carbonate agarcontaining ethanol as energy source. The clearingaround the colonies due to the dissolution of calciumcarbonate by the acetic acid produced by the bacteria

Classified as Gluconobacter

Can carry out incomplete oxidation of higher alcohol and sugars:Glucose Gluconic acidGalactose Galactonic acidArabinose Arabonic acidSorbitol Sorbose Ascobic acid

Zymomonas and Chromobacterium Facultatively aerobic gram-negative rods, beta purple bacteria Chromobacterium violaceum produces a purple pigment violacein, a water-insolubl

e pigment that has antibiotic properties and is produced only from tryptophan Zymomonas carries out fermentation of sugar to ethanol, used in beverage industry.

A large colony of Chromobacterium violaceumgrowing among other colonies on an agar plate

Pigment violacein produced byvarious species of the genusChromobacterium

Vibrio and Related Genera

Gram-negative, facultatively aerobic rods and curved rodsthat possess a fermentative metabolismMost are aquatic. The Group contains Vibrio, Aeromonas, PhotobacteriumSome can emit light (luciferase luciferase), these are associated with fish.

and Plesiomonas