• Proteobacteria is considered the major group of bacteria.They include a wide variety of pathogens,. Others are free-living (non-parasitic), and include many of the bacteriaresponsible for nitrogen fixation.

• The name was taken from the mythological Greek godProteus, who could assume many shapes.

1. Alphaproteobacteria

2. Betaproteobacteria

3. Gammaproteobacteria

4. Deltaproteobacteria

5. Epsilonproteobacteria

• These are gram-negative rod-shaped bacera, or coccobacilli. They aretransmitted to humans by bites of insects and ticks. They are alsoresponsible for a number of disease known as the spotted fever group.

• Are gram-negative, rickettsialike bacteria that live obligately within white blood cells.

• Are both found in low-nutrients aquatic environments, such as lakes. They both produce prominent prosthecae (budding).

• Rhizobium and Bradyrhizobium are two of the more important genera of a group of agriculturally important bacteria that specifically infect the roots of leguminous plants.

• It’s presence in the roots leads to formation of nodules in which the rhizobia and plant form a symbiotic relationship, resulting in the fixation of nitrogen from the air for use by the plant.

• Contains several members that are human pathogens.

• The best example known is Bartonella henselae, a gram-negative bacillus that causes cat-scratched disease.

• Are small nonmotile coccobacilli. Species of Brucella are obligate parasites of mammals and cause the disease brucellosis. It has the ability to survive phagocytosis.

• Are genera of nitrifying bacteria that are of great importance to the environment and to agriculture. They are chemoautotrophs capable of using inorganic chemicals as energy sources and carbon dioxide as the only source of carbon, from which they synthesize all of their complex chemical makeup.

• Are probably the most common infectious bacterial genus in the world. They live only inside the cells of their hosts, usually insects (a relationship known as endosymbiosis).

• These are sulfur-oxidizing bacteria. They are chemoautotrophicbacteria capable of obtaining energy by oxidizing the reduced forms ofsulfur, such as hydrogen sulfide (H2S), or elemental sulfur, into sulfates(SO4).

• It’s habitat is mainly fresh water. They are motile byconventional polar flagella, rather than axial fillament. Theyare relatively large, gram-negative, aerobic bacteria.

Burkholderia• These were formerly group with Pseudomonas, a

gammaproteobacteria. Like Pseudomonas, all Burkholderiaspecies are motile by a single polar flagellum or tuft of flagella.

Bordetella• Is the nonmotile, aerobic, gram-negative rod Bordetella

pertussis. This serious pathogen is the cause of pertussis, or whooping cough.

• These are aerobic, gram-negative cocci that usually inhabit the mucous membrane of mammals.

Zoogloea• These genus is important in the context of aerobic sewage-

treatment processes. As they grow, Zoogloea bacteria form fluffy, slimy masses that are essential to the proper operation of such systems.

• Is a genus of small

pleomorphic bacteria that

grow only on complex

media enriched with blood

or tissue extracts.

• Strictly aerobic coccobacilli that is intermediate in shape between cocciand rods.

• Each cell has one polar flagellum.

• It is frequently found in raw meat,

particularly chicken, and thus is a

significant cause of food poisoning

due to handling raw meat or

undercooking it.

•

.

Clostridiales

ARCHAEA• Halophiles

1. Halobacterium – bacteria that survive in very high concentrations of salt, such as the Great Salt Lake and solar evaporating ponds.

2. Sulfolobus – archaea that thrive in acidic, sulfur-rich hot springs.

• Hyperthermophiles

1. Methanobacterium – anaerobic methane-prodcingmembers of archaea.

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