proteobacteria. largest and most diverse group of bacteria (450 genera) sometimes called purple...
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Proteobacteria
Proteobacteria
Largest and most diverse group of bacteria (450 genera)
Sometimes called purple bacteria
Purple photosynthetic bacteria found in , , and classes
Proposed that proteobacteria arose from a photosynthetic ancestor
Class Alphaproteobacteria
Composed of 6 orders and 18 families
Purple nonsulfur bacteria
Use anoxygenic photosynthesis
All except Rhodocyclus () are found in the -proteobacteria
Considerable variation in morphology
Genus Rickettsia
Order Rickettsiales, Family Rickettsiaceae
Contains species that cause disease in animals
Genus Rickettsia
Can grow in vertebrate erythrocytes, macrophages and vascular endothelial cells
Blood-sucking arthropods often serve as vectors
Prostheca bacteria
A prostheca is an extension of the cell that is narrower than the cell
Two of the best studied examples are the genera Caulobacter and Hyphomicrobium
Hyphomicrobium life cycle
Caulobacter life cycle
Stalk lacks cytoplasmic contents
May improve efficiency of nutrient uptake (increased surface area)
Caulobacter life cycle
Family Rhizobiaceae
Belongs to the order Rhizobiales
Contains 2 important genera:
Rhizobium
Agrobacterium
Rhizobium
Grow within root nodules of legumes as nitrogen-fixing symbionts
Agrobacterium
Does not stimulate nodule formation or nitrogen-fixation
Invades plant cells and induces the formation of a tumor
Ability to induce tumor formation is dependent on a plasmid
Nitrifying bacteria
Located in the alpha, beta and gamma proteobacteria
Oxidize either ammonia to nitrite or nitrite to nitrate
Play an important role in the ecology of soil
Nitrifying bacteria
Class Betaproteobacteria
Composed of 7 orders and 12 families
Order Neisseriales
Composed of a single family (Neisseriaceae) with 14 genera
Most studied genus is Neisseria
Aerobic diplococci with capsules and fimbriae
N. gonorrhoeae and N. meningitidis are human pathogens
Order Burkholderiales
Contains 4 families
Genus Burkholderia in the family Burkholderiaceae
Previously grouped with Pseudomonas
Burkholderia cepacia is a plant and human pathogen (Cystic fibrosis patients)
Order Burkholderiales
Family Alcaligenaceae contains the genus Bordetella
Bordetella pertussis is the cause of whooping cough
Order Hydrogenophilales
Contain the colorless sulfur bacteria (are also found in the )
Includes the genus Thiobacillus
Genus Thiobacillus
Grow aerobically by oxidizing various sulfur containing compounds
Can tolerate very acidic conditions
Production of sulfuric acid by T. ferrooxidans can corrode metal and concrete
Class Gammaproteobacteria
Constitutes the largest subgroup of proteobacteria
Divided into 14 orders and 25 families
Class Gammaproteobacteria
Order Chromatiales /Purple sulfur bacteria
Divided into 2 families
Are strict anaerobes that oxidize hydrogen sulfate to S0 and deposit it as intracellular sulfur granules
Order Methylococcales
Use methane, methanol and other reduced one-carbon compounds as both their sole carbon and energy sources
Referred to as methylotrophs
Contains the genera Methylococcus and Methylomonas
Order Pseudomonadales
Most important genus in the order is Pseudomonas
Many can degrade a wide variety of organic molecules
Some are pathogens of animals and plants
Orders Vibrionales, Enterobacteriales and Pasteurellales
Closely related orders that each contain a single family
Order Vibrionales
Several are bioluminescent
Can be free-living or live symbiotically in the luminous organs of fish
Order Vibrionales
Vibrio cholerae and V. parahaemolyticus are human pathogens
Other species cause diseases in fish
Order Enterobacteriales
Composed of one family (Enterobacteriaceae) with over 40 genera
Often referred to as enteric bacteria
Can be distinguished by their different metabolic properties
Order Enterobacteriales
Order Enterobacteriales
E. coli is the best studied bacterium
Many members of this order are pathogens including Salmonella, Shigella, Klebsiella, Yersinia and Erwinia
Order Pasteurellales
Composed of a single family with 6 genera
Members of the family cause diseases in humans and animals
Pasteurella multilocida and P. haemolytica are animal pathogens
Haemophilus influenzae is a human pathogen
Class Deltaproteobacteria
Composed of 7 orders and 18 families
Orders Desulfovibrionales, Desulfobacterales and Desulfuromonadales
Are all anaerobes that use S0, sulfate and other sulfur containing compounds as electron acceptors during anaerobic respiration
Very important for the cycling of sulfur within the ecosystem
Order Bdellovibrionales
Composed of one family with 4 genera
Members of the genus Bdellovibrio prey on other gram-negative bacteria
Order Myxococcales
Aerobic soil bacteria with gliding motility
Exhibit a complex life cycle
Class Epsilonproteobacteria
The smallest class of proteobacteria
Composed of one order and three families
Two important genera are Campylobacter and Helicobacter
Both contain human and animal pathogenic species