title: Gene expression and deletion analysis of mechanisms for electron transfer from electrodes to Geobacter sulfurreducens.
abstract: Geobacter sulfurreducens is one of the few microorganisms available in pure culture known to directly accept electrons from a negatively poised electrode. Microarray analysis was used to compare gene transcript abundance in biofilms of G. sulfurreducens using a graphite electrode as the sole electron donor for fumarate reduction compared with transcript abundance in biofilms growing on the same material, but not consuming current. Surprisingly, genes for putative cell-electrode connections, such as outer-surface cytochromes and pili, which are highly expressed in current-producing biofilms, were not highly expressed in current-consuming biofilms. Microarray analysis of G. sulfurreducens gene transcript abundance in current-consuming biofilms versus current-producing biofilms gave similar results. In both comparative studies current-consuming biofilms had greater transcript abundance for a gene (GSU3274) encoding a putative monoheme, c-type cytochrome. Deletion of genes for outer-surface proteins previously shown to be essential for optimal electron transfer to electrodes had no impact on electron transfer from electrodes. Deletion of GSU3274 completely inhibited electron transfer from electrodes, but had no impact on electron transfer to electrodes. These differences in gene expression patterns and the impact of gene deletions suggest that the mechanisms for electron transfer from electrodes to G. sulfurreducens differ significantly from the mechanisms for electron transfer to electrodes.
authors.affiliation: Department of Microbiology, 203N Morrill Science Center IVN, University of Massachusetts Amherst, 639 N. Pleasant St., Amherst, Massachusetts 01003, USA. sarah.strycharz.ctr@nrl.navy.mil
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Strycharz
authors.forename: Richard H
authors.initials: RH
authors.lastname: Glaven
authors.forename: Maddalena V
authors.initials: MV
authors.lastname: Coppi
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Gannon
authors.forename: Lorrie A
authors.initials: LA
authors.lastname: Perpetua
authors.forename: Anna
authors.initials: A
authors.lastname: Liu
authors.forename: Kelly P
authors.initials: KP
authors.lastname: Nevin
authors.forename: Derek R
authors.initials: DR
authors.lastname: Lovley
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018441:Biofilms; D003580:Cytochromes / Q000235:genetics / Q000378:metabolism; D004566:Electrodes; D004579:Electron Transport / Q000235:genetics*; D004583:Electrons; D015870:Gene Expression; D045302:Geobacter / Q000235:genetics / Q000378:metabolism; D006108:Graphite / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D010084:Oxidation-Reduction; D017384:Sequence Deletion / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D003580:Cytochromes; D006108:Graphite