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.