Azotobacter vinelandii DJ

Azotobacter vinelandii is a free-living, obligately aerobic, nitrogen-fixing gamma-proteobacteria. It is found in soils world-wide, with features of nitrogen and energy metabolism relevant to agriculture. In response to carbon starvation it differentiates to form cysts that are impervious to chemical and physical challenge. Studies have been focused on its ability to fix diatmospheric nitrogen under free-living conditions, a process that occurs in the presence of oxygen levels that typically inactivate the nitrogenase enzyme. Unusually it encodes three distinct nitrogenase systems, the molybdenum, vanadium and iron-only nitrogenases, expression of which is differentially regulated by metal availability from the medium. Diazotrophic growth under aerobic conditions is possible because it adjusts oxygen-consumption rates to help maintain low levels of cytoplasmic oxygen, a phenomenon called respiratory protection. It is able to produce alginate, a polymer that further protects the organism from excess exogenous oxygen, and it has multiple duplications of alginate modification genes, which may alter alginate composition in response to oxygen availability. Other oxygen-sensitive enzymes have also been identified in the genome (carbon monoxide dehydrogenase, a formate dehydrogenase, and another hydrogenase). Genome annotation was done by supervised teams of undergraduate students using a web-based system over a preliminary automated annotation, both developed by J. C. Setubal (adapted from PubMed 19429624). (EBI Integr8)