Microbial regulatory mechanisms involved in groundwater arsenic enrichment: Synergistic interactions between key species and genes in C-N-S metabolism

Microbially mediated carbon (C), nitrogen (N), and sulfur (S) metabolism are core biogeochemical drivers affecting arsenic (As) mobilization and transformation that regulate the formation of high-arsenic groundwater globally. This study determined the microbial molecular mechanisms driving As mobility via coupled C-N-S cycles in the Kuitun River Basin (Xinjiang, China). Metagenomic and geochemical analyses of high-As (HA; >10 μg/L, n = 5) and low-As (LA; ≤10 μg/L, n = 6) samples revealed significant microbial community divergence (analysis of similarities R = 0.67, P = 0.003). Key differential genera included HA-enriched Candidatus Kuenenia and Sulfuritalea as well as the LA-enriched Sphingobium and Novosphingobium. Key functional genes exhibited contrasting As correlations, with negative correlations (katE, cynT, ncd2, ssuABC, and dmdC) in LA-dominant Rhodopseudomonas/Hydrogenophaga/Acinetobacter promoting As³⁺ oxidation, competitive inhibition of As⁵⁺ reduction, and As₂S₃ precipitation; positive correlations (ACO, korA, hao, psrA) in HA-associated Candidatus Kuenenia and Thiobacillus enhanced As⁵⁺ reduction, Fe/Mn oxide dissolution, and thioarsenate formation. Rhodopseudomonas in unconfined aquifers demonstrated a synergistic C-N-S network (katE-ncd2-ssuABC) for efficient As immobilization. These findings enhance the understanding of microbially driven As biogeochemical cycles and provide a theoretical foundation for developing in situ remediation technologies based on microbial metabolic regulation.