Article

Possible nonconductive role of Geobacter sulfurreducens pilus nanowires in biofilm formation

Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Journal of Bacteriology (Impact Factor: 2.69). 04/2007; 189(5):2125-7. DOI: 10.1128/JB.01284-06
Source: PubMed

ABSTRACT Geobacter sulfurreducens required expression of electrically conductive pili to form biofilms on Fe(III) oxide surfaces, but pili were also essential for biofilm development on plain glass when fumarate was the sole electron acceptor. Furthermore, pili were needed for cell aggregation in agglutination studies. These results suggest that the pili of G. sulfurreducens also have a structural role in biofilm formation.

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Available from: Gemma Reguera, Sep 22, 2014
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    • "Pili are known to have an important role in biofilm formation (Moreira et al., 2006; Reguera et al., 2007; Oxaran et al., 2012; Snider et al., 2012), but also for the conductive properties of Geobacter biofilms (Summers et al., 2010; Malvankar "
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    ABSTRACT: Interspecies exchange of electrons enables a diversity of microbial communities to gain energy from reactions that no one microbe can catalyze. The first recognized strategies for interspecies electron transfer were those that relied on chemical intermediates that are recycled through oxidized and reduced forms. Well-studied examples are interspecies H2 transfer and the cycling of sulfur intermediates in anaerobic photosynthetic communities. Direct interspecies electron transfer (DIET) in which two species establish electrical contacts is an alternative. Electrical contacts documented to date include electrically conductive pili, as well as conductive iron minerals and conductive carbon moieties such as activated carbon and biochar. Interspecies electron transfer is central to the functioning of methane-producing microbial communities. The importance of interspecies H2 transfer in many methanogenic communities is clear, but under some circumstances DIET predominates. It is expected that further mechanistic studies and broadening investigations to a wider range of environments will help elucidate the factors that favor specific forms of interspecies electron exchange under different environmental conditions.
    Frontiers in Microbiology 05/2014; 5. DOI:10.3389/fmicb.2014.00237 · 3.94 Impact Factor
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    • "(iii) non-conductive nanowires as a foremost structural factor for cell aggregation and biofilm formation as described for pili of metal-reducing bacteria , e.g. Geobacter sulfurreducens (Reguera et al., 2007). "
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    • "Similarities between electron transfer to insoluble Fe(III) oxides and electrodes include requirements for the electrically conductive pili [10] [15] [16] and the outer membrane c-type cytochrome, OmcS [11] [17]. "
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    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.
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