Desulfurivibrio spp. drives sulfur-oxidizing Sb(V) reduction process in antimony contaminated regions

Antimony (Sb) contamination released from mine tailings is a severe environmental threat to both the local ecosystem and exposed human populations. In Sb-associated mine tailings, the S- and Sb- rich geochemical conditions may promote specific biogeochemical processes. In the current study, a novel biogeochemical Sb cycling, i.e., S-oxidizing Sb(V) reduction, was observed in the cultures inoculated from Sb mine tailings. Bacteria associated with the genus Desulfurivibrio were identified as the S-oxidizing Sb(V) reducing bacteria (S-oxidizing SbRB) by stable isotope probing. The retrieved metagenome assembled genome (MAG) revealed that the Desulfurivibrio-associated MAG possesses necessary genes for Sb(V) reduction and S oxidation, which further confirmed its role as S-oxidizing SbRB. Other genetic evidence demonstrated its potential contribution to the ecosystem by carbon fixation, nitrogen fixation, and phosphate acquisition. Investigation of environmental samples from Sb mining impacted regions suggested Desulfurivibrio constituted a significant fraction of the tailing microbial community, but not in other Sb contaminated environments (i.e. adjacent soils, paddies, and river sediments). Panmetagenomic analysis revealed the ability to couple S-oxidation and Sb(V) reduction was a conserved genetic trait for Desulfurivibrio residing in metal-contaminated sites in southern China. The identification of putative S-oxidizing SbRB provided a possible management strategy to reduce Sb's environmental impact in the future.

矿山尾矿释放的锑（Sb）污染，对当地生态系统及暴露人群均构成严重环境威胁。在含锑的矿山尾矿中，富硫与富锑的地球化学环境可促进特定生物地球化学过程的发生。本研究从锑矿尾矿接种的培养物中，观测到一种新型生物地球化学锑循环过程——硫氧化型锑(V)还原过程。通过稳定同位素探针（stable isotope probing）技术，鉴定出隶属于脱硫弧菌属（Desulfurivibrio）的细菌为该过程的硫氧化型锑(V)还原菌（S-oxidizing SbRB）。所获取的宏基因组组装基因组（metagenome assembled genome, MAG）显示，关联脱硫弧菌属的MAG携带锑(V)还原与硫氧化所需的必要功能基因，进一步证实了其作为硫氧化型锑(V)还原菌的功能角色。其他遗传学证据表明，该菌具备通过固碳、固氮与磷获取为生态系统做出贡献的潜力。对受锑矿开采影响区域的环境样本的调查显示，脱硫弧菌属在尾矿微生物群落中占据显著比例，但在其他受锑污染环境（如邻近土壤、稻田与河流沉积物）中则并非如此。泛宏基因组分析（Panmetagenomic analysis）揭示，耦合硫氧化与锑(V)还原的能力，是栖息于中国南方金属污染场地的脱硫弧菌属的保守遗传性状。本次推定的硫氧化型锑(V)还原菌的鉴定，为未来降低锑的环境影响提供了可行的管理策略。