Identification of Microbial Communities in Open and Closed Circuit Bioelectrochemical MBRs by High-Throughput 454 Pyrosequencing

Two bioelectrochemical membrane bioreactors (MBRs) developed by integrating microbial fuel cell and MBR technology were operated under closed-circuit and open-circuit modes, and high-throughput 454 pyrosequencing was used to investigate the effects of the power generation on the microbial community of bio-anode and bio-cathode. Microbes on the anode under open-circuit operation (A(O)) were enriched and highly diverse when compared to those on the anode under closed-circuit operation (A(C)). However, among the cathodes the closed-circuit mode (C(C)) had richer and more diverse microbial community compared to the cathode under open-circuit mode (C(O)). On the anodes A(O) and A(C), Proteobacteria and Bacteroidetes were the dominant phyla, while Firmicutes was enriched only on A(C). Deltaproteobacteria affiliated to Proteobacteria were also more abundant on A(C) than A(O). Furthermore, the relative abundance of Desulfuromonas, which are well-known electrogenic bacteria, were much higher on A(C) (10.2%) when compared to A(O) (0.11%), indicating that closed-circuit operation was more conducive for the growth of electrogenic bacteria on the anodes. On the cathodes, Protebacteria was robust on C(C) while Bacteroidetes was more abundant on C(O). Rhodobacter and Hydrogenophaga were also enriched on C(C) than C(O), suggesting that these genera play a role in electron transfer from the cathode surface to the terminal electron acceptors in the bioelectrochemical MBR under closed-circuit operation.