Long-range electron conduction of Shewanella biofilms mediated by outer membrane C-type cytochromes

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• 作者：Akihiro Okamoto^a ; Kazuhito Hashimoto^a ; ^b ; ^{hashimoto@light.t.u-tokyo.ac.jp} ; Ryuhei Nakamura^a ; ^{nakamura@light.t.u-tokyo.ac.jp}
• 关键词：Conductive biofilm ; Cytochrome ; MFC ; Whole-cell voltammetry ; Extracellular ET
• 刊名：Bioelectrochemistry
• 出版年：2012
• 期刊代码：7_15675394
• 类别：ch
• 出版时间：June, 2012
• 卷：85
• 期：Complete
• 页码：61-65
• 文件大小：927 K

摘要

We investigated the role of c-type cytochromes (c-Cyts) in electron conduction across biofilms of Shewanella oneidensis MR-1 and the relevance of the electron conductivity for biological current generation. Following the formation of monolayer and multilayer biofilms on indium-tin oxide electrodes, we quantified the c-Cyts that were electrically wired with the electrode surface using whole-cell voltammetry. A multilayer biofilm with a thickness of 16 渭m exhibited a redox peak with an 8-fold larger coulombic area than that of a monolayer biofilm (about 0.5-渭m thickness), indicating an abundance of c-Cyts that are able to perform redox-cycling reactions with the distant electrode surface. To determine if this electron conduit of c-Cyts participated in biological current generation, we conducted slow-scan voltammetry for multilayer biofilms. A large anodic current of c-Cyts caused by microbial lactate oxidization was observed during the slow-potential scans, demonstrating the transport of respiratory electrons via the sequential redox cycling of c-Cyts. Experiments with deletion mutants deficient in outer-membrane (OM) c-Cyts (螖mtrC/螖omcA, 螖pilD), and the biosynthetic protein of capsular polysaccharide (螖SO3177) suggested that cell-surface-bound c-Cyts, but those located on pili or extracellular polymeric substrates, play a predominant role in the long-range electron conduction in the biofilm of S. oneidensis MR-1.