Evidence for the presence of a b-type cytochrome in the sulfate-reducing bacterium Desulfovibrio gigas, and its role in the reduction of fumarate by molecular hydrogen

Abstract

1. The H 2:fumarate reductase activities of particulate fractions prepared from Desulfovibrio gigas grown on various media (lactate-sulfate, fumarate or fumarate-sulfate) were measured. Activity was higher in the particulate fraction prepared from cells grown on fumarate or fumarate-sulfate media than in those prepared from cells cultivated on lactate-sulfate. 2. Various inhibitors were tested for their effect on fumarate reduction by H 2 in a particulate fraction of Desulfovibrio gigas. A strong inhibitory effect was observed with 2-hetyl-4-hydroxyquinoline- N-oxide and antimycin A. These compounds act as inhibitors of an intermediary electron carrier between hydrogenase and fumarate reductase. 3. The strict anaerobe Desulfovibrio gigas has been found to contain a b-type cytochrome linked to the particulate H 2:fumarate reductase activity. A protoheme obtained by extraction from the particulate fraction was characterized by its reduced pyridine hemochromogen.