Abstract

Electroactive bacteria export metabolic electrons through cytochrome-based extracellular electron-transfer (EET) conduits. Although purified S. oneidensis EET cytochromes are chiral and spin-selective, the functional impact of chirality-induced spin selectivity in live cultures remains unknown. Here, we show that a magnetic field enhances current in live S. oneidensis. EET to non-magnetic electrodes increased by ~70 %, whereas electron uptake was insensitive to magnetic field. In contrast, electron uptake increased by >100 % when spin-polarised electrons were supplied from a magnetised electrode. This directional response suggests that magnetic field improves spin matching in the EET conduit, but only when the incoming electron flux is spin-polarised, implying that metabolic electrons are already spin-polarised before entering the conduit. Cytochromes in the conduit were downregulated despite higher current, indicating enhanced EET efficiency.