Engineering electron conduits in bacteria for selective biointerfacing and enhanced energy transfer

Specialized cytochrome protein complexes conduct electrons across cell membranes in electrogenic bacteria, which enables these microbes to be harnessed for applications in electrical generation, biosensing, and microbial electrosynthesis. Here, we engineer the surface-exposed MtrC subunit from the MtrCAB complex of Shewanella oneidensis to enable selective cell attachment to functional materials, including electrodes for improved bioelectricity production. Incorporating a SpyTag bioconjugation domain on MtrC enables specific covalent attachment of SpyCatcher-fused proteins to MtrCAB on S. oneidensis and Escherichia coli. Importantly, the MtrC modification does not disrupt electron export, offering opportunities to interface cells with electronic materials. In the second approach, incorporating a graphite binding sequence on MtrC improves S. oneidensis attachment to graphite electrodes, yielding 30% greater current production in a microbial electrolysis cell compared to a variant expressing unmodified MtrC. An engineerable platform on the surface of electrogenic cells creates numerous opportunities for biotic-abiotic interface manipulation.