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Gene Expression by the Sulfate-Reducing Bacterium Desulfovibrio vulgaris Hildenborough Grown on an Iron Electrode under Cathodic Protection Conditions ^,

Sean M. Caffrey,^1, Hyung Soo Park,^1, Jenny Been,^2, Paul Gordon,³ Christoph W. Sensen,³ and Gerrit Voordouw^1*

Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada,¹ NOVA Research and Technology Corporation, 2928 16th Street NE, Calgary, Alberta, Canada,² Sun Center of Excellence for Visual Genomics, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada³

Received 1 November 2007/ Accepted 15 February 2008

The genome sequence of the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough was reanalyzed to design unique 70-mer oligonucleotide probes against 2,824 probable protein-coding regions. These included three 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 overexpressed two hydrogenases, the hyn-1 genes for [NiFe] hydrogenase 1 and the hyd genes, encoding [Fe] hydrogenase. The hmc genes for the high-molecular-weight cytochrome complex, which allows electron flow from the hydrogenases across the cytoplasmic membrane, were also overexpressed. In contrast, cells grown on gaseous hydrogen overexpressed the hys genes for [NiFeSe] hydrogenase. Cells growing on the electrode also overexpressed 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 hyn-1, hyd, and hmc mutant biofilms than for wild-type biofilms. This confirms the importance, suggested by the gene expression studies, of the corresponding gene products in D. vulgaris-mediated iron corrosion.

Published ahead of print on 29 February 2008.

Supplemental material for this article may be found at http://aem.asm.org/.

These two authors contributed equally to this article.

Present address: Corrosion Engineering, Advanced Materials, Alberta Research Council, 3608 33rd Street NW, Calgary, Alberta T2L 2A6, Canada.