Multiomics Insights into Antimony Methylation Driven by Sulfate-Reducing Bacteria in Paddy Soil

Abstract Antimony (Sb) is a toxic element of global concern that accumulates in rice, threatening food security and human health. In anaerobic paddy soils, Sb risks depend strongly on microbially mediated speciation transformations. Methylation may enhance Sb mobility and potential toxicity under associated reducing conditions, thereby imposing a selective pressure on resident microbial communities. However, the mechanisms driving Sb methylation have remained poorly understood. Here, multiomics analysis of an anaerobic enrichment culture from Sb-contaminated paddy soil revealed an Sb methylation and resistance network led by transcriptionally dominant Desulfovibrionales, with contributions from Eubacteriales and Bacteroidales. Genome-resolved metabolic reconstruction reveals that this core lineage deploys a coordinated dual defense strategy against Sb toxicity. Intracellularly, arsC-mediated reduction may facilitate arsM-mediated methylation, while arsP-mediated efflux may contribute to methylated Sb export and cellular detoxification. Extracellularly, elevated dsrAB transcription suggests that sulfate-reduction-related sulfur transformations may contribute to the extracellular sequestration of soluble inorganic Sb(III), potentially reducing its bioavailability. Overall, this study provides insights into microbial pathways associated with Sb methylation, particularly in Desulfovibrionales, and highlights the importance of considering methylated species alongside inorganic Sb in future assessments of Sb mobility and rice uptake, as well as in the development of mitigation strategies for paddy ecosystems.