Deletion of the Desulfovibrio vulgaris Carbon Monoxide Sensor Invokes Global Changes in Transcription

The carbonmonoxide-sensing transcriptional factor CooA has been studied only in hydrogenogenic organisms that can grow using CO as the sole source of energy. Homologs for the canonical CO oxidation system, including CooA, CO dehydrogenase (CODH), and a CO-dependent Coo hydrogenase, are present in the sulfate-reducing bacteriumDesulfovibrio vulgaris, although it grows only poorly on CO.We show thatD. vulgarisHildenborough has an active CO dehydrogenase capable of consuming exogenous CO and that the expression of the CO dehydrogenase, but not that of a gene annotated as encoding a Coo hydroge-nase, is dependent on both CO and CooA. Carbonmonoxide did not act as a general metabolic inhibitor, since growth of a strain deleted for cooAwas inhibited by CO on lactate-sulfate but not pyruvate-sulfate. While the deletion strain did not accumulate CO in excess, as would have been expected if CooA were important in the cycling of CO as a metabolic intermediate, global tran-scriptional analyses suggested that CooA and CODH are used during normal metabolism. Desulfovibrio organisms are sulfate-reducing bacteria that useorganic acids, alcohols, or molecular hydrogen as electron donors to reduce sulfate (22). When these bacteria grow on or-ganic acids or alcohols, energy generation is hypothesized to be derived in part through hydrogen cycling (20). Hydrogen cycling posits that reducing equivalents formed during oxidation of the electron donor in the cytoplasm are shuttled to form hydrogen