# 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

## TL;DR

Adding Shewanella oneidensis MR-1 to iron mine soil biofilms boosts electricity production and changes the microbial community structure over time.

## Contribution

This study shows how introducing an exoelectrogen alters microbial community dynamics and enhances biofilm electrochemical performance.

## Key findings

- Co-cultured biofilms achieved a higher maximum power density (195 ± 8 mW/m2) than iron mine soil or Shewanella biofilms alone.
- Pelobacteraceae abundance increased significantly in co-cultured biofilms, while Rhodocyclaceae decreased.
- Shewanella's relative abundance in co-cultures decreased over time, becoming similar to that in iron mine soil.

## Abstract

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 Shewanella (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 (p = 0.02) increased, while that of Rhodocyclaceae was significantly (p = 0.008) decreased, compared with that in iron mine soil biofilms. After continuing the experiment for two months, the presence of Shewanella oneidensis MR-1 changed the predominant bacteria of the microbial community in the biofilms, and the relative abundance of Shewanella was significantly (p = 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.