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摘要：The persistent use of antibiotics has exacerbated the spread of antibiotic-resistant bacteria (ARB) and antibioticresistant genes (ARGs) in aquatic environments, including drinking water systems. Pipeline biofilms, comprising over 95 % of microbial biomass, function as high-risk reservoirs for ARG accumulation and horizontal gene transfer (HGT). However, the roles of disinfection-induced biofilm aggregation in plasmid-mediated conjugation remains mechanistically obscure. This study investigated how sodium hypochlorite (NaClO), chlorine dioxide (ClO2), and their combination affect ARB selection and ARG conjugation in multispecies drinking water biofilms at environmentally relevant chlorine concentrations (0–2.0 mg/L). Results showed that exposure to either NaClO or ClO2 at 1.0 mg/L increased the relative abundance of ARB, while combined disinfection at 2.0 mg/L exerted selective pressure that further enhanced ARB enrichment. Sublethal chlorine levels increased conjugation frequencies within biofilms by 2.1- to 5.9-fold relative to untreated controls. Conjugation efficiency was positively correlated with bacterial surface colonization and metabolic activity (r = 0.95, p < 0.05). Mechanistic investigations revealed that chlorine exposure upregulated integrase genes, enriched potential ARG-hosting taxa, and preserved fimbrial structures, collectively facilitating donor-recipient interactions and promoting HGT. These findings elucidate the mechanistic pathways underlying disinfection-mediated horizontal gene transfer and provide critical insights into managing antibiotic resistance risks in drinking water systems.

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收录刊物：SCI