S157: Electron transfer mechanism in Shewanella loihica PV- 4 biofilms formed at indium tin oxide and graphite electrodes

Extracellular Electron Transfer (EET) mechanisms in Shewanella loihica PV-4 viable biofilms formed at indium tin oxide (ITO) and graphite electrodes were investigated in potentiostat-controlled electrochemical cells (EC) poised at oxidative potentials (0.2 V vs. Ag/AgCl). Chronoamperometry (CA) showed a repeatable biofilm growth on both electrode materials. The anodic current density on graphite electrodes was 20 times higher than that on ITO electrodes. Direct electron transfer (DET) mechanism is prevalent at the biofilm/ITO interface while biofilm formed at graphite electrode avails of soluble redox mediators (SRM) as well as electrode-bound redox mediators (BRM), along with outer membrane c type cytochromes (Omcs). Nearly 50 % of the overall current generation by S. loihica PV-4 biofilm on graphite is due to mediated electron transfer mechanism (MET) via SRM, regardless of the biofilm age. In young biofilms, the rest of the current result from DET through Omcs and MET via BRM. In old biofilms, the electrons are transferred predominantly via MET, likely because of the accumulation of BRM at the biofilm/graphite interface.