Novel Photoelectron-Assisted Microbial Reduction of Arsenate Driven by Photosensitive Dissolved Organic Matter in Mine Stream Sediments

The microbial reduction of arsenate (As(V)) significantly contributes to arsenic migration in mine stream sediment, primarily driven by heterotrophic microorganisms using dissolved organic matter (DOM) as a carbon source. This study reveals a novel reduction pathway in sediments that photosensitive DOM generates photoelectrons to stimulate diverse nonphototrophic microorganisms to reduce As(V). This microbial photoelectrophic As(V) reduction (PEAsR) was investigated using microcosm incubation, which showed the transfer of photoelectrons from DOM to indigenous sediment microorganisms, thereby leading to a 50% higher microbial reduction rate of As(V). The abundance of two marker genes for As(V) reduction,