Premium
Microarray and genetic analysis of electron transfer to electrodes in Geobacter sulfurreducens
Author(s) -
Holmes Dawn E.,
Chaudhuri Swades K.,
Nevin Kelly P.,
Mehta Teena,
Methé Barbara A.,
Liu Anna,
Ward Joy E.,
Woodard Trevor L.,
Webster Jennifer,
Lovley Derek R.
Publication year - 2006
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2006.01065.x
Subject(s) - geobacter sulfurreducens , biology , cytochrome , gene , transcriptome , bacterial outer membrane , gene expression , cytochrome c , dna microarray , gene expression profiling , microbiology and biotechnology , biochemistry , enzyme , genetics , bacteria , biofilm , mitochondrion , escherichia coli
Summary Whole‐genome analysis of gene expression in Geobacter sulfurreducens revealed 474 genes with transcript levels that were significantly different during growth with an electrode as the sole electron acceptor versus growth on Fe(III) citrate. The greatest response was a more than 19‐fold increase in transcript levels for omcS , which encodes an outer‐membrane cytochrome previously shown to be required for Fe(III) oxide reduction. Quantitative reverse transcription polymerase chain reaction and Northern analyses confirmed the higher levels of omcS transcripts, which increased as power production increased. Deletion of omcS inhibited current production that was restored when omcS was expressed in trans. Transcript expression and genetic analysis suggested that OmcE, another outer‐membrane cytochrome, is also involved in electron transfer to electrodes. Surprisingly, genes for other proteins known to be important in Fe(III) reduction such as the outer‐membrane c ‐type cytochrome, OmcB, and the electrically conductive pilin ‘nanowires’ did not have higher transcript levels on electrodes, and deletion of the relevant genes did not inhibit power production. Changes in the transcriptome suggested that cells growing on electrodes were subjected to less oxidative stress than cells growing on Fe(III) citrate and that a number of genes annotated as encoding metal efflux proteins or proteins of unknown function may be important for growth on electrodes. These results demonstrate for the first time that it is possible to evaluate gene expression, and hence the metabolic state, of microorganisms growing on electrodes on a genome‐wide basis and suggest that OmcS, and to a lesser extent OmcE, are important in electron transfer to electrodes. This has important implications for the design of electrode materials and the genetic engineering of microorganisms to improve the function of microbial fuel cells.