Cyclic voltammetric analysis of the electron transfer of Shewanella oneidensis MR-1 and nanofilament and cytochrome knock-out mutants

Shewanella is frequently used as a model microorganism for microbial bioelectrochemical systems. In this study, we used cyclic voltammetry (CV) to investigate extracellular electron transfer mechanisms from S. oneidensis MR-1 (WT) and five deletion mutants: membrane bound cytochrome (Delta mtrC/Delta omcA), transmembrane pili (Delta pilM-Q, Delta mshH-Q, and Delta pilM-Q/Delta mshH-Q) and flagella (Delta flg). We demonstrate that the formal potentials of mediated and direct electron transfer sites of the derived biofilms can be gained from CVs of the respective biofilms recorded at bioelectrocatlytic (i.e. turnover) and lactate depleted (i.e. non-turnover) conditions. As the biofilms possess only a limited bioelectrocatalytic activity, an advanced data processing procedure, using the open-source software SOAS, was applied. The obtained results indicate that S. oneidensis mutants used in this study are able to bypass hindered direct electron transfer by alternative redox proteins as well as self-mediated pathways. (C) 2011 Elsevier B.V. All rights reserved.