Chlorination level-dependent amplification of antibiotic resistance genes dissemination by chlorinated paraffins via ROS-mediated natural transformation

The widespread dissemination of antibiotic resistance genes (ARGs) across the globe poses a growing and significant threat to both environmental and human health. Chlorinated paraffins (CPs) are extensively used worldwide and are increasingly detected across diverse environmental compartments. However, the impact of CPs on ARGs dissemination remains inadequately understood. This study systematically evaluates the effects of CPs (C10 - C30 mixture) with varying chlorination levels (CPs42, CPs52, CPs58) on ARGs spread in aquatic environments, utilizing a natural transformation (NT) model based on the plasmid pWH1274 and Acinetobacter baylyi ADP1. The results demonstrated that bacterial exposure to CPs induced the production of reactive oxygen species (ROS), which increased with rising CPs concentrations and chlorination levels. Lethality was observed at high CPs concentrations (e.g., 100 - 400   mg/L). Mechanistic investigations revealed that CPs-enhanced ARG dissemination primarily occurs through ROS-driven facilitation of natural transformation. Further analysis indicated this enhancement stems from ROS-mediated processes that elevated bacterial cellular competence and recombinational activity. Critically, our findings confirm that the risk of ARGs dissemination amplification escalates with increasing chlorination levels of CPs. This work advances our understanding of the environmental risks associated with CPs and provides crucial theoretical foundations for mitigating their detrimental effects.