Diazotroph
From Freepedia
Diazotrophs are microorganisms that 'fix' atmospheric nitrogen gas in to a more usable form such as ammonia. Examples of organisms that do this are rhizobia and Frankia (in symbiosis) and Azospirillum. A diazotroph is an organism that is able to grow without external sources of fixed nitrogen. All diazotrophs contain iron-molybdenum nitrogenase systems. Two of the most studied systems are those of Klebsiella pneumoniae and Azotobacter vinlandii. These systems are used because of their genetic tractability and their fast growth 1.
Note 1: Dixon R and Kahn D. 2004. Genetic regulation of biological nitrogen fixation. Nat Rev Microbiol. 2(8):621-31.
