Electron Transport through Early Exponential-Phase Anode-Grown Geobacter sulfurreducens Biofilms

Geobacter sulfurreducens biofilms were grown to early exponential phase (i.e. the point at which the catalytic current first begins to increase) on interdigitated microelectrode arrays (IDAs), resulting in the formation of sparse cell clusters surrounded by extracellular polymeric substance (EPS). Continuous domains of EPS (defined here to include extracellular materials including filaments), but not cell clusters, were observed to bridge the gaps between adjacent electrode bands. Electrochemical gate measurements revealed electrical continuity between adjacent IDA electrode bands, indicating that extracellular electron transport (EET) occurs through the EPS. The dependency of the source-drain current on the gate potential is peak shaped, which is consistent with EPS acting as a redox conductor. The gate potential at which the maximum source-drain current occurs is approximately 0.13V more positive than that for stationary-phase biofilms, indicating that redox cofactors involved in EET at the early exponential phase are different to those at the stationary phase. Bridging the gap:- Geobacter Sulfurreducens biofilms are grown to an early exponential phase on interdigitated microelectrode arrays, (IDAs) resulting in the formation of cell clusters surrounded by extracellular polymeric substance (EPS). Continuous domains of EPS, but not of cell clusters, were observed to bridge the gaps between adjacent electrodes. Electrochemical gate measurements reveal electrical continuity between adjacent IDA electrodes, indicating that electron transport through the biofilm does not require cell-to-cell contact, but can occur through EPS.