Effect of electrode potentials on the microbial community of photo bioelectrochemical systems

Increasing attention is being paid to the adoption of photoautotrophic microbes in bioelectrochemical systems (BESs) because of the advantages of self-sustainability. Biased potential on the anode was capable of adjusting the performance of non-photo BESs, and the microbial community structure was also changed; however, few studies have been conducted to investigate the effects of potential on microbial community structure in photo-BESs. In this work, the response of microbial community structure to different potentials (i.e., 0, 0.2, 0.4 and 0.6 V vs. Ag/AgCl) was characterized with 454 pyrosequencing. Four samples were collected and they generated 42865 16S rDNA sequencing reads with an average length of 429 bp. The potential at 0.2 V resulted in the highest current density (378.8 mA m^-2) and showed a strong selection for γ-proteobacteria (30.8% of the sequences). α-Diversity analysis showed that microbial diversity increased with increased potential. Rhodopseudomonas palustris was dominant among known exoelectrogens in the biofilm biased at 0.4 V. The results provided an insight into the mechanism of potential regulation on the performance of photo-BESs and changes in microbial community structure.