In-situ nano-encapsulation of living cells with polydopamine for enhanced artificial interspecies electron transfer.

Interspecies electron transfer (IET) determines the efficiency of electro-syntrophic metabolism in electroactive microbial communities. Compared with mediated IET (MIET) mediated by diffusible electron shuttles, contact-based direct IET (DIET) can enable more efficient energy transfer. However, engineering DIET is constrained by the challenges of maintaining stable and conductive cell-to-cell interfaces. In this study, we developed a conductive and adhesive interface by in-situ polydopamine (PDA) nano-encapsulation of Shewanella oneidensis MR-1 (SW, electron donating partner) surfaces. The coating promoted stable and intimate coaggregation of SW with Rhodopseudomonas palustris (RP, electron accepting partner). This cell-to-cell PDA interface promoted a shift in the dominant IET mode from H2-mediated MIET toward contact-dependent electron transfer involving outer membrane C-type cytochromes. Notably, nitrogenase-derived CH4, used as a quantitative indicator of IET efficiency, increased by ∼380 % in the engineered two-species community. This study provided a simple and promising approach for IET manipulation, which may open new avenue for microbial community engineering of electro-syntrophic systems.