Isolation of nitrogen-fixing bacteria containing molybdenum-independent nitrogenases from natural environments

Seven diazotrophs that grow well under Mo-deficient, N(2)-fixing conditions were isolated from a variety of environments. These isolates fall in the gamma subdivision of the class Proteobacteria and have genes that encode the Mo nitrogenase (nitrogenase 1) and the V nitrogenase (nitrogenase 2). Four of the isolates also harbor genes that encode the iron-only nitrogenase (nitrogenase 3).