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Appl. Environ. Microbiol. doi:10.1128/AEM.02469-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Gene expression of the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough grown on an iron electrode under cathodic protection conditions

Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada; NOVA Research and Technology Corporation, 2928 16th Street NE, Calgary, Alberta, Canada; Sun Center of Excellence for Visual Genomics, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada

^* To whom correspondence should be addressed. Email: voordouw{at}ucalgary.ca.

	Abstract

The genome sequence of the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough was reanalyzed to design unique 70-mer oligonucleotide probes against 2824 probable protein-coding regions. These included 3 genes, not previously annotated, including one that encodes a c-type cytochrome. Using microarrays, printed with these 70-mer probes, we analyzed the gene expression profile of wild-type D. vulgaris grown on cathodic hydrogen, generated at an iron electrode surface with an imposed negative potential of -1.1 V (cathodic protection conditions). The gene expression profile of cells grown on cathodic hydrogen was compared to that of cells grown with gaseous hydrogen bubbling through the culture. Relative to the latter, the electrode-grown cells over-expressed two hydrogenases, the hyn1 genes for [NiFe] hydrogenase-1, and the hyd genes, encoding [Fe] hydrogenase. The hmc genes for the high molecular weight cytochrome (Hmc) complex, which allows electron flow from the hydrogenases across the cytoplasmic membrane, were also over-expressed. In contrast, cells grown on gaseous hydrogen over-expressed the hys genes for [NiFeSe] hydrogenase. Cells growing on the electrode also over-expressed genes encoding proteins which promote biofilm formation. Although the gene expression profiles for these two modes of growth were distinct, they were more closely related to each other than to that for cells grown in a lactate- and sulfate-containing medium. Electrochemically measured corrosion rates were lower for iron electrodes covered with hyn1-, hyd-, and hmc-mutant biofilms, as compared to wild-type biofilms. This confirms the importance, suggested by the gene expression studies, of the corresponding gene products in D. vulgaris-mediated iron corrosion.