Evolution of Shewanella oneidensis MR-1 in competition with Citrobacter freundii

Interspecific competition is one of the most important metabolic interactions within microbial communities, and exoelectrogenic bacteria that can conduct extracellular electron transfer act essential roles in nature and engineering systems for pollutants removal. In the present study we investigated the long-term impact of substrate competition from non-exoelectrogenic Citrobacter freundii An1 on exoelectrogenic Shewanella oneidensis MR-1. Without additional electron acceptor or with electron acceptor of oxygen, C. freundii An1 typically suppressed the growth of S. oneidensis MR-1. In contrast, S. oneidensis MR-1 grown better with electron acceptor of ferrihydrite by taking advantage of extracellular electron transfer. However, the presence of ferrihydrite did not enhance the ferrihydrite reduction of S. oneidensis MR-1 after the 160 d-acclimation. The whole genome resequencing showed a complex evolution of S. oneidensis MR-1 when the strain faced the competition from C. freundii An1 for substrate.