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

## TL;DR

Scientists engineered bacteria to better connect with materials like electrodes, improving electricity production and opening new possibilities for biotechnology.

## Contribution

A new platform for selectively interfacing electrogenic bacteria with electronic materials using modified cytochrome complexes.

## Key findings

- Modifying MtrC with SpyTag allows specific protein attachment to electrogenic bacteria.
- Adding a graphite-binding sequence to MtrC increases electricity production by 30% in microbial electrolysis cells.
- Modified MtrC functions across species, including Escherichia coli.

## Abstract

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.

•Shewanella oneidensis uses MtrCAB conduits to move electrons across the outer membrane•Fusion of SpyTag to the MtrC subunit enabled selective fluorescent bioconjugation•Graphite binding domain fusion to MtrC improved electrode binding and energy transfer•Cross-species compatibility of modified MtrC was demonstrated in Escherichia coli

Shewanella oneidensis uses MtrCAB conduits to move electrons across the outer membrane

Fusion of SpyTag to the MtrC subunit enabled selective fluorescent bioconjugation

Graphite binding domain fusion to MtrC improved electrode binding and energy transfer

Cross-species compatibility of modified MtrC was demonstrated in Escherichia coli

Bioengineering; Microbial biotechnology