Journal
BIOELECTROCHEMISTRY
Volume 85, Issue -, Pages 61-65Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.bioelechem.2011.12.003
Keywords
Conductive biofilm; Cytochrome; MFC; Whole-cell voltammetry; Extracellular ET
Funding
- Japan Science and Technology Agency (JST)
- Japan Society for Promotion of Science (JSPS) [00218864]
- Grants-in-Aid for Scientific Research [09J08864] Funding Source: KAKEN
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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 pm exhibited a redox peak with an 8-fold larger coulombic area than that of a monolayer biofilm (about 0.5-mu 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 (Delta mtrC/Delta omcA, Delta pilD), and the biosynthetic protein of capsular polysaccharide (Delta 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. (C) 2011 Elsevier B.V. All rights reserved.
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