A Microbial Cell Coating Based on a Conjugated Polyelectrolyte with Broad Reduction Potential Increases Inward and Outward Extracellular Electron Transfer

Bioelectrochemical systems hold the promise of enabling sustainable microbial-mediated energy interconversion between electrical and chemical energy. Herein, it is demonstrated how a single conjugated polymer can be used to enhance bidirectional extracellular electron transfer through forming self-assembled coatings on individual cells. Specifically, the n-type conjugated polyelectrolyte p(cNDI-gT2) exhibits a reduction potential window between -0.1 and -0.8 V (vs Ag/AgCl), thereby driving thermodynamically favored electron transfer in both directions across the abiotic-biotic interface that involves the outer membrane cytochromes and flavins of Shewanella oneidensis MR-1. Electrochemical tests show that injection from an external electrode into Shewanella oneidensis MR-1 is enabled at negative potentials (-0.6 V), while electron extraction is possible at positive potentials (0.2 V). Relative to controls, the biohybrid shows a sixfold increase in biocurrent generation and a 35-fold increase in current uptake for the bioelectrosynthesis of succinate from fumarate. This demonstrated abiotic-biotic synergy provides new strategies for designing multifunctional biohybrids.