Antimonite (Sb(III)) oxidation (SbO) can decrease the toxicity of antimony (Sb) and its uptake into rice, thus serving an ecological role in bioremediation of Sb contamination in rice paddies and decreasing the translocation and accumulation of Sb in rice. Nitrate as the electron acceptor can be coupled to SbO in anoxic environments, which, however, has not been reported in paddy soils. Here we investigate the potential for nitrate-dependent SbO in Sb-contaminated rice paddies and identify nitrate-dependent Sb(III)-oxidizing bacteria (SbOB) using stable isotope probing (SIP) coupled with amplicon and shotgun metagenomic sequencing. Anaerobic SbO was exclusively observed in the paddy soil amended with both Sb(III) and NO₃⁻, whereas no apparent SbO was detected in the soil amended with Sb(III) only. The increasing abundance of the arsenite oxidase gene (aioA) suggests that nitrate-dependent SbO was catalysed by microorganisms harbouring the aioA gene. After 60-day DNA-SIP incubation, an obvious shift in the relative abundance of aioA gene to heavy DNA fractions occurred only in the treatment amended with ¹³C–NaHCO₃, Sb(III) and NO₃⁻, suggesting the incorporation of ¹³C by nitrate-dependent SbOB. Accordingly, a number of putative nitrate-dependent SbOB were identified in the paddy soil, including Azoarcus, Azospira and Chelativorans. Metagenomic analysis further revealed that they contained aioA genes and genes involved in denitrification and carbon fixation, supporting their capability for nitrate-dependent SbO. These observations suggested the occurrence of nitrate-dependent SbO in paddy soils. A number of putative nitrate-dependent SbOB (i.e., Azoarcus, Azospira and Chelativorans) were reported here, which expands our current knowledge regarding the diversity of nitrate-dependent SbOB. In addition, this study provides a proof of concept using DNA-SIP to identify nitrate-dependent SbOB.

锑（Sb（III））氧化（SbO）可以降低锑（Sb）的毒性及其对水稻的吸收，从而在稻田中Sb污染的生物修复中起到生态作用，并减少Sb在水稻中的转运和积累。在缺氧环境中，硝酸盐作为电子受体可以与SbO偶联，但是在水稻土中尚未见报道。在这里，我们调查了受Sb污染的稻田中硝酸盐依赖性SbO的潜力，并使用稳定同位素探测（SIP）结合扩增子和shot弹枪宏基因组测序，鉴定了硝酸盐依赖性Sb（III）氧化细菌（SbOB）。厌氧非晶态SbO与两个锑（III）和NO修正稻田土壤是专门观察到₃ ^-，而在仅用Sb（III）改良的土壤中未检测到明显的SbO。亚砷酸氧化酶基因（aioA）的丰度增加表明，硝酸盐依赖性SbO被具有aioA基因的微生物催化。经过60天的DNA-SIP温育后，在的相对丰度的明显移位aioA基因重DNA级分只发生在与修正处理¹³ C-的NaHCO ₃，锑（III）和NO ₃ ^- ，这表明掺入¹³ C由硝酸盐依赖性SbOB决定。因此，数推定的硝酸盐依赖性SbOB在稻田土壤进行了鉴定，包括固氮弧菌，Azospira和螯虾。元基因组学分析进一步表明，它们包含aioA基因以及涉及反硝化和碳固定的基因，从而支持其依赖硝酸盐的SbO的能力。这些观察结果表明在水稻土中存在硝酸盐依赖性的SbO。一些假定的硝酸盐依赖性SbOB（的即，固氮弓，Azospira和Chelativorans）在这里报道，扩大有关硝酸盐依赖性SbOB的多样性我们现有的知识。此外，这项研究提供了使用DNA-SIP识别硝酸盐依赖性SbOB的概念证明。