@article {481, title = {Genome-wide gene expression patterns and growth requirements suggest that Pelobacter carbinolicus reduces Fe(III) indirectly via sulfide production.}, journal = {Appl Environ Microbiol}, volume = {74}, year = {2008}, month = {2008 Jul}, pages = {4277-84}, abstract = {Although Pelobacter species are closely related to Geobacter species, recent studies suggested that Pelobacter carbinolicus may reduce Fe(III) via a different mechanism because it lacks the outer-surface c-type cytochromes that are required for Fe(III) reduction by Geobacter sulfurreducens. Investigation into the mechanisms for Fe(III) reduction demonstrated that P. carbinolicus had growth yields on both soluble and insoluble Fe(III) consistent with those of other Fe(III)-reducing bacteria. Comparison of whole-genome transcript levels during growth on Fe(III) versus fermentative growth demonstrated that the greatest apparent change in gene expression was an increase in transcript levels for four contiguous genes. These genes encode two putative periplasmic thioredoxins; a putative outer-membrane transport protein; and a putative NAD(FAD)-dependent dehydrogenase with homology to disulfide oxidoreductases in the N terminus, rhodanese (sulfurtransferase) in the center, and uncharacterized conserved proteins in the C terminus. Unlike G. sulfurreducens, transcript levels for cytochrome genes did not increase in P. carbinolicus during growth on Fe(III). P. carbinolicus could use sulfate as the sole source of sulfur during fermentative growth, but required elemental sulfur or sulfide for growth on Fe(III). The increased expression of genes potentially involved in sulfur reduction, coupled with the requirement for sulfur or sulfide during growth on Fe(III), suggests that P. carbinolicus reduces Fe(III) via an indirect mechanism in which (i) elemental sulfur is reduced to sulfide and (ii) the sulfide reduces Fe(III) with the regeneration of elemental sulfur. This contrasts with the direct reduction of Fe(III) that has been proposed for Geobacter species.}, keywords = {Acetoin, Cytochrome c Group, Deltaproteobacteria, Ethanol, Fermentation, Ferric Compounds, Gene Expression Profiling, Genome, Bacterial, Iron, Nitrilotriacetic Acid, Oligonucleotide Array Sequence Analysis, Oxidation-Reduction, Reverse Transcriptase Polymerase Chain Reaction, RNA, Bacterial, Substrate Specificity, Sulfides, Sulfur, Sulfur-Reducing Bacteria, Thioredoxins}, issn = {1098-5336}, doi = {10.1128/AEM.02901-07}, author = {Haveman, Shelley A and Didonato, Raymond J and Villanueva, Laura and Shelobolina, Evgenya S and Postier, Bradley L and Xu, Bo and Liu, Anna and Lovley, Derek R} } @article {480, title = {Insights into genes involved in electricity generation in Geobacter sulfurreducens via whole genome microarray analysis of the OmcF-deficient mutant.}, journal = {Bioelectrochemistry}, volume = {73}, year = {2008}, month = {2008 Jun}, pages = {70-5}, abstract = {Geobacter sulfurreducens effectively produces electricity in microbial fuel cells by oxidizing acetate with an electrode serving as the sole electron acceptor. Deletion of the gene encoding OmcF, a monoheme outer membrane c-type cytochrome, substantially decreased current production. Previous studies demonstrated that inhibition of Fe(III) reduction in the OmcF-deficient mutant could be attributed to poor transcription of the gene for OmcB, an outer membrane c-type cytochrome that is required for Fe(III) reduction. However, a mutant in which omcB was deleted produced electricity as well as wild type. Microarray analysis of the OmcF-deficient mutant versus the wild type revealed that many of the genes with the greatest decreases in transcript levels were genes whose expression was previously reported to be upregulated in cells grown with an electrode as the sole electron acceptor. These included genes with putative functions related to metal efflux and/or type I secretion and two hypothetical proteins. The outer membrane cytochromes, OmcS and OmcE, which previous studies have demonstrated are required for optimal current generation, were not detected on the outer surface of the OmcF-deficient mutant even though the omcS and omcE genes were still transcribed, suggesting that the putative secretion system could be involved in the export of outer membrane proteins necessary for electron transfer to the fuel cell anode. These results suggest that the requirement for OmcF for optimal current production is not because OmcF is directly involved in extracellular electron transfer but because OmcF is required for the appropriate transcription of other genes either directly or indirectly involved in electricity production.}, keywords = {Bacterial Outer Membrane Proteins, Cytochromes c, Down-Regulation, Electricity, Gene Expression Regulation, Bacterial, Genome, Bacterial, Geobacter, Mutation, Oligonucleotide Array Sequence Analysis, Transcription, Genetic}, issn = {1567-5394}, doi = {10.1016/j.bioelechem.2008.04.023}, author = {Kim, Byoung-Chan and Postier, Bradley L and Didonato, Raymond J and Chaudhuri, Swades K and Nevin, Kelly P and Lovley, Derek R} }