Metaproteomic and Metagenomic Coupled Approach to Investigate Microbial Response to Electrochemical Conditions in Microbial Fuel Cell

Microbial fuel cells (MFCs) can mediate the direct conversion of organic matter from wastewater into electricity using bacterial biofilms as biocatalysts. One of the critical points in MFCs is to understand which electroactive bacteria and which mechanisms are involved in the extracellular electron transfer to the anode. The goal of this study was to evaluate how an applied voltage between anode and cathode influences the anodic bacterial community structure and activity. Two MFCs were operated with an external resistance of 1000 ohms. One was submitted to an applied electrical voltage of 500 mV during the first four days of biofilm formation and the other was started without additional applied voltage. When the electricity production was stable, both total DNA and total protein were extracted and sequenced. The combined metaproteomic / metagenomic approach shows that when a voltage was applied during the colonization step, a direct electron transfer via cytochrome c was the major mechanism detected and mainly mediated by Geobacter sp. With the other MFC, a higher diversity of bacteria, such as Pseudomonas and Aeromonas, seemed to be involved in the electricity production using mediated electron transfer via flavin family members when no voltage was applied during the colonization step.