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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