Derepression of nitrogenase activity in glutamine auxotrophs of Rhodopseudomonas capsulata

In contrast to wild-type cells, glutamine auxotrophs of the photosynthetic bacterium Rhodopseudomonas capsulata synthesize nitrogenase, produce H2 (catalyzed by nitrogenase), and continue to reduce dinitrogen to ammonia in the presence of exogenous NH4+. The glutamine synthetase activity of such mutants is less than 2% of that observed in the wild type. It appears that glutamine synthetase plays a significant role in regulation of nitrogenase synthesis in R. capsulata.