The use of metronidazole to study pyridine nucleotide reduction in vivo in Azotobacter vinelandii

Abstract

Flavins of the particulate and supernatant fractions from nitrogen-fixing Azotobacter vinelandii cells were examined by fluorescence spectroscopy for reduction by NAD(P)H in the absence and presence of the low potential electron acceptor metronidazole. The objective was to determine if reduction of metronidazole-oxidized flavin in vivo results from NAD(P)H generation. Flavin was almost completely reduced by NADH, but NADPH gave less reduction. Most of the flavin was reduced in the presence of metronidazole. Menadione bisulfite prevented reduction. In whole-cell studies, mannitol-generated NAD(P)H reduced flavin in the presence of menadione bisulfite. These results establish that reduction of metronidazole-oxidized cell flavin in vivo is an indicator of NAD(P)H production.Key words: metronidazole, NAD(P)H reduction, Azotobacter vinelandii.