Question

1. What are the “firmicutes” (give examples with importance)? What bacteria are found in the α (alpha), β (beta), γ (gamma) Proteobacteria groups, indicating their importance.

Answer 1

Ans1- Firmicutes- The Firmicutes are a phylum of bacteria, most of which have Gram-positive cell wall structure. A few, however, such as Megasphaera, Pectinatus, Selenomonas and Zymophilus, have a porous pseudo-outer- membrane that causes them to stain Gram-negative.

• Firmicutes word is taken from Latin words firmus means strong, and cutis means skin, referring to the cell wall.
• All firmicutes forms endosopre  which are resistant to desiccation and can survive extreme conditions.
• The endospore consists of the bacterium’s DNA and part of its cytoplasm, surrounded by a very tough outer coating.
• Endospores can survive without nutrients and they are resistant to ultraviolet radiation, desiccation, high temperature, extreme freezing and chemical disinfectant.
• They have low G+C ratio.
• some of them are present in human gut.
• Obese individuals present predominance of Firmicutes.

Ans 2- Proteobacteria groups,-

Alpha-

Agrobacterium	Gram-negative bacillus	Plant pathogen; one species, A. tumefaciens, causes tumors in plants
Bartonella	Gram-negative, pleomorphic, flagellated coccobacillus	Facultative intracellular bacteria, transmitted by lice and fleas, cause trench fever and cat scratch disease in humans
Brucella	Gram-negative, small, flagellated coccobacillus	Facultative intracellular bacteria, transmitted by contaminated milk from infected cows, cause brucellosis in cattle and humans

beta -

Bordetella	A small, gram-negative coccobacillus	Aerobic, very fastidious; B. pertussis causes pertussis (whooping cough)
Burkholderia	Gram-negative bacillus	Aerobic, aquatic, cause diseases in horses and humans (especially patients with cystic fibrosis); agents of nosocomial infections
Leptothrix	Gram-negative, sheathed, filamentous bacillus	Aquatic; oxidize iron and manganese; can live in wastewater treatment plants and clog pipes

gamma-

Escherichia	Gram-negative bacillus	Facultative anaerobe; inhabit the gastrointestinal tract of warm-blooded animals; some strains are mutualists, producing vitamin K; others, like serotype E. coli O157:H7, are pathogens; E. coli has been a model organism for many studies in genetics and molecular biology
Hemophilus	Gram-negative bacillus	Pleomorphic, may appear as coccobacillus, aerobe, or facultative anaerobe; grow on blood agar; pathogenic species can cause respiratory infections, chancroid, and other diseases

Vibrio

Gram-negative, comma- or curved rod-shaped bacteria

Inhabit seawater; flagellated, motile; may produce toxin that causes hypersecretion of water and electrolytes in the gastrointestinal tract; some species may cause serious wound infections