Biological sulfur oxidation mediated arsenate reduction, a key process in arsenic-contaminated habitats

Arsenate reduction is a major cause of As release from soils which threatens more than 200 million people worldwide. While heterotrophic As(V) reduction has been extensively investigated, the mechanism of chemolithotrophic As(V) reduction is less studied. Since As is frequently found as sulfidic minerals in the environment, microbial-mediated sulfur oxidation coupled to As(V) reduction (SOAsR), a chemolithotrophic process, may be more favorable in oligotrophic mining-impacted sites (e.g., As-contaminated mine tailings). While SOAsR is thermodynamically favorable, knowledge regarding this biogeochemical process is still limited. The current study suggested that SOAsR was a more dominant process compared to heterotrophic As(V) reduction in oligotrophic sites, such as mine tailings. A combination of DNA-SIP and metagenome binning revealed members of the genera Sulfuricella, Ramlibacter, and Sulfuritalea as SOAsRBs in mine tailings. Genome mining further expanded the list of SOAsRBs to diverse phylogenetic lineages such as members associated with Burkholderiaceae and Desulfuribacteraceae. Meta-analysis using multiple tailing sample metagenomes across southern China confirmed that the putative SOAsRB were the dominant As(V) reducers in these sites. Together, the current findings expand our knowledge regarding the chemolithotrophic As(V) reduction process, which may be harnessed to facilitate future remediation practices in mine tailings.