Regulation of Nitrogenase Activity in Rhodopseudomonas capsulata

Regulation o f nitrogenase activity in Rhodopseudomonas capsulata AD 2 differs in several respects from other Rhodospirillaceae: 1) Nitrogenase activity in this strain grown under severe N-starvation was fully derepressed, but in contrast to other Rhodospirillaceae, it was inhibited by am m onia in vivo. 2) Nitrogenase in extracts o f glutamate grown cells was fully active and not further stimulated by Mn2+. 3) Treatment of N-starved or glutamate grown cells with ammonia before harvest did not cause inactivation of nitrogenase in vitro.