Abstract
Hypoiodous acid (HIO) represents a pivotal iodine species in global iodine cycling, yet microbial contributions to its transformation have remained poorly characterised. Here, we demonstrate that the metal‐reducing bacterium Shewanella oneidensis MR‐1 actively drive HIO reduction to iodide. Notably, genetic disruption of extracellular electron transfer components impaired HIO reduction activity in S. oneidensis MR‐1. Specifically, Δ mtrCAB reduced 49.7% less HIO than the wild type within 10 min, while Δ dmsEFAB exhibited a slight impairment in HIO reduction. The mutants lacking outer‐membrane c ‐type cytochromes (MtrC and OmcA) also showed substantially lower reduction efficiencies (29.6%–54.0%) than wild type. Although flavin secretion was not essential for HIO reduction in S. oneidensis MR‐1, reduced riboflavin chemically reacted with HIO to generate iodide. Importantly, both the mtrC / omcA deletions and exogenous HIO addition inhibited iodate reduction, suggesting HIO reduction serves as a detoxification mechanism. In contrast, electron shuttles dose‐dependently enhanced iodate reduction. Collectively, these results demonstrate that Shewanella ‐mediated HIO reduction constitutes a rapid detoxifying pathway for HIO, with the MtrCAB‐OmcA transmembrane electron conduit acting as the primary mediator. However, the DmsEFAB pathway and endogenous electron shuttles showed limited contributions.