Spatial variation of electrical conductance in electrochemically active biofilm growing on interdigitated microelectrode array

Abstract

Revealing the pathways of electron transport within electrochemically active biofilms (EABs) is of great importance. Here, mixed-culture EABs are grown on three interdigitated microelectrode arrays (IDAs) with different gap widths of 10 μm, 20 μm and 50 μm and their conductances are determined. The maximum conductive current increases with the decrease of the gap width and charge transfer resistance obtained for the biofilm attaching on the electrode is 3–11 fold less than that for biofilm bridging gaps, suggesting high conductance of biofilm closer to the electrode surface. Results from Raman analysis show high abundance of multi-heme cytochromes in biofilm bridging 10 μm gap, leading to small resistance of biofilm growing on the IDA with 10 μm gap. In addition, the maximum conductive current of biofilm bridging gaps at the potential of −0.40 V vs. Ag/AgCl suggests that electron transfer in biofilm growing on IDAs is redox driven. All these results indicate the spatial heterogeneity of electron transport processes acting within biofilm.