antimony and arsenic co-contaminated river sedimentary microbial community in an antimony-contaminated river Raw sequence reads. antimony and arsenic co-contaminated river sedimentary microbial community in an antimony-contaminated river

Antimony (Sb) and arsenic (As) are toxic elements that occur widely in trace soil concentrations. Expansion of mining activities has increased Sb and As pollution, posing a severe threat to human welfare and ecological systems worldwide. Knowledge regarding the behavior and composition of the microbial communities in these metal(loid) contaminated sites is still limited. In the current study, five sedimentary sites along a stream flowing through the world’s largest Sb mining area (Xikuangshan) were selected to investigate the microbial response to various Sb or As fractions. A comprehensive analysis of geochemical parameters, high-throughput sequencing, and statistical methods were applied to reveal the different effects of Sb and As on sedimentary microorganisms. The results suggested that the majority of the Sb and As fractions were not bioavailable. The Sb extractable fraction had a greater effect on the microbial community compared with its As counterpart. Random forest analyses indicated that the easily exchangeable Sb fraction and specifically sorbed surface-bound fraction were the two most selective variables shaping microbial community diversity. Several potential keystone taxa, such as bacteria associated with the phyla Bacteroidetes, Proteobacteria, and Firmicutes, were identified according to a molecular ecological network analysis. Strong correlations (|R| > 0.7, P < 0.05) were observed between the indigenous microbial community and pH (negative), sulfate (negative), and exchangeable Sb fraction (positive). Bacteria associated with the genera Geobacter, Phormidium, Ignavibacterium, Desulfobulbus, and Arthronema were predicted to tolerate or metabolize the Sb extractable fraction.