Differential Mechanisms of Microbial As(III) and Sb(III) Oxidation and Their Contribution to Tailings Reclamation

Mine tailings are extremely oligotrophic environments frequently contaminated with elevated As and Sb, making As­(III) and Sb­(III) oxidation potentially important energy sources for the tailing microbiome. Although they have been proposed to share similar metabolic pathways, a systemic comparison of the As­(III) and Sb­(III) oxidation mechanisms and energy utilization efficiencies requires further elucidation. In this study, we employed a combination of physicochemical, molecular, and bioinformatic analyses to compare the kinetic and genetic mechanisms of As­(III) and Sb­(III) oxidation as well as their respective energy efficiencies for fueling the key nutrient acquisition metabolisms. Thiobacillus and Rhizobium spp. were identified as functional populations for both As­(III) and Sb­(III) oxidation in mine tailings by DNA-stable isotope probing. However, these microorganisms mediated As­(III) and Sb­(III) oxidation via different metabolic pathways, resulting in preferential oxidation of Sb­(III) over As­(III). Notably, both As­(III) and Sb­(III) oxidation can facilitate nitrogen fixation and phosphate solubilization in mine tailings, with Sb­(III) oxidation being more efficient in powering these processes. Thus, this study provided novel insights into the microbial As­(III) and Sb­(III) oxidation mechanisms and their respective nutrient acquisition efficiencies, which may be critical for the reclamation of mine tailings.