Dynamic Potential-Dependent Electron Transport Pathway Shifts in Anode Biofilms of Geobacter sulfurreducens

Biofilms of the anode-respiring bacterium Geobacter sulfurreducens (G. sulfurreducens) demonstrate dynamic potential-dependent changes between two electron transport pathways that are used selectively depending on the anode potential. Electrochemical impedance spectroscopy (EIS) measurements suggest that these pathways (both n=1), with midpoint potentials of -0.155 (+/- 0.005) and -0.095 (+/- 0.003) V versus standard hydrogen electrode, are not additive within the biofilm, but are preferentially used depending on the anode potential. Potential step voltammetry and cyclic voltammetry (CV) confirmed rapid changes between the two pathways in minutes when the anode potential is changed. We confirm that the electrochemical response observed in a slow-scan-rate CV (similar to 1 mVs(-1)) is often composed of at least the two pathways characterized. Thus, beyond understanding the electron transport pathways in G. sulfurreducens, this study also has implications on the interpretation of previously collected and future potential-dependent datasets.