Electricity Production and Population Dynamics of Microbial Community in a Co-Culture of Iron Mine Soil Biofilm and Shewanella oneidensis MR-1 with Anode as Electron Acceptor

Microbial communities that develop within biofilms on electrodes are necessary for the proper functioning of the microbial electrochemical system. However, the mechanism through which an exogenous exoelectrogen influences the population dynamics and electrochemical performance of biofilms remains unclear. In this study, we explored the community structure dynamics and electrochemical characteristics of iron mine soil biofilm co-cultured with Shewanella oneidensis MR-1, with the anode as the electron acceptor, and compared the results with those of iron mine soil biofilms alone on the anode. Shewanella oneidensis MR-1 improved the electrochemical activity of microbial biofilms, resulting in a higher maximum power density of 195 ± 8 mW/m² compared with that of iron mine soil (175 ± 7 mW/m²) and <i>Shewanella</i> (88 ± 8 mW/m²) biofilms individually. The co-cultured biofilms could perform near the highest power density for a longer duration than the iron mine soil biofilms could. High-throughput 16S rRNA gene sequencing of the biofilms on the anode indicated that the relative abundance of Pelobacteraceae in the co-culture system was significantly (<i>p</i> = 0.02) increased, while that of Rhodocyclaceae was significantly (<i>p</i> = 0.008) decreased, compared with that in iron mine soil biofilms. After continuing the experiment for two months, the presence of <i>Shewanella oneidensis</i> MR-1 changed the predominant bacteria of the microbial community in the biofilms, and the relative abundance of <i>Shewanella</i> was significantly (<i>p</i> = 0.02) decreased to a level similar to that in iron mine soil. These results demonstrate that Shewanella oneidensis MR-1 could improve the performance of iron mine soil biofilms in electrochemical systems by altering the composition of the functional microbial communities.