The following description comes mainly from Garrity et al. (2003).  
I. SYNONYMS: β-proteobacteria, nitrogen-fixing bacteria, .  


A. Structure

Cell Form: Variable; rods, cocci, spirals; and filaments.

Cell Wall: Gram-.

Motility: Non-motile or motile; some are mobile (move without flagella in contact with a substrate).

B. Physiology

O2 Tolerance: Aerobes or facultative anaerobes.

Substrates: Some obtain their carbon from CO2 and a variety of organic sources.  Electron sources are sulfur compounds and hydrogen.  Others utilize ammonium and other nitrogen compounds.  Most are chemoorganotrophs and chemolithotrophs.

Products: They produce a variety of oxidized carbon, nitrogen, and sulfur compounds.

C. Other: Very diverse group of bacteria.

D. Ecology: Free-living in soils and aquatic sediments; some are nodule-formers.



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By Jack R. Holt.  Last revised: 02/18/2013