| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1267255 | Bioelectrochemistry | 2012 | 5 Pages |
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 μm exhibited a redox peak with an 8-fold larger coulombic area than that of a monolayer biofilm (about 0.5-μm 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 (ΔmtrC/ΔomcA, ΔpilD), and the biosynthetic protein of capsular polysaccharide (ΔSO3177) 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.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The role of bacterial c-Cyts for electron conductivity across Shewanella biofilms. ► Whole-cell cyclic voltammetry quantified bacterial c-Cyts in the biofilm on electrodes. ► Multilayer biofilm showed the larger redox current of c-Cyts than monolayer biofilm. ► The long-range electron transfer contributes bacterial anode current generation. ► Mutant experiments revealed electron conduction by c-Cyts along cellular surface.
