Electricity-powered cryptic CO₂ fixation pathway in heterotrophic Shewanella oneidensis for acetate synthesis

Microbial electrosynthesis of CO₂ is a sustainable carbon neutral technology. Although known for its diverse and efficient extracellular electron transfer (EET) characteristics, the bacteria of Shewanella genus have never been reported for use in electrosynthesis of multi-carbon chemicals. Herein, the electricity-powered conversion of CO₂ to acetate was achieved under ammonium regulation for the first time in the model strain (Shewanella oneidensis MR-1), due to the activation of its intrinsic reductive glycine pathway. A high electron flux from cathode into MR-1 was achieved through the unique electron uptake pathway mediated by endogenous iron release, biomineralization of iron oxide, and inherent EET pathways. Consequently, MR-1 delivered an acetate production rate of 78.6 ± 4.2mmol m^-2 d^-1, significantly surpassing those of previously reported electro-autotrophic acetogens under similar operating conditions. Our findings not only provide a novel platform for one-carbon biorefinery, but also prompt recognition to the complexity of EET and CO₂ fixation.