Dissolved organic matter-generated photoelectrons enable microbial antimonate reduction in mine stream sediments

Antimony contamination in mining-impacted river basins poses persistent environmental risks, yet the microbial processes governing antimony redox transformation under anoxic sediments remain poorly understood. Here, we report that photoelectrons generated by naturally occurring dissolved organic matter can support microbial antimonate reduction. Natural dissolved organic matter exhibits sustained photocurrent responses under illumination. In anoxic microcosms, indigenous sediment communities achieve 50-70% antimonate reduction with photoelectron supply, thereby constraining purely abiotic reduction or alternative electron-donor explanations under our experimental conditions. Multi-omics further identify non-phototrophic taxa (e.g., Sphingomonas and Bosea) with elevated antimony reduction/detoxification pathways and respiratory electron-transfer components under photoelectron exposure. The consistent presence of photosensitive dissolved organic matter and candidate taxa across mining-impacted sediments suggests broader environmental relevance. These findings indicate that photosensitive dissolved organic matter may provide a photoelectron flux that influences microbial antimony redox transformations in anoxic sediments.