Evidence for an alternative nitrogenase in<i>Heliobacterium gestii</i>

Abstract

The anoxygenic phototrophic bacterium Heliobacterium gestii grew and fixed dinitrogen in molybdenum-deficient media when either iron or iron plus vanadium were present. Cultures grown on N2 with iron or iron plus vanadium reduced acetylene to both ethylene and ethane; molybdenum-grown cultures did not produce ethane. Cultures of Heliobacterium chlorum and Heliobacillus mobilis were unable to grow and fix dinitrogen in media devoid of molybdenum. It is concluded that H. gestii can synthesize an iron-only alternative nitrogenase under appropriate culture conditions.