Environmental concentrations of per/polyfluoroalkyl substances promote the conjugative transfer of antibiotic resistance genes

Per/polyfluoroalkyl substances (PFAS) are widespread in aquatic environments and pose significant risks to human health. Their roles in the spread of antibiotic resistance genes through conjugation were investigated in the laboratory. Results showed that PFAS including Perfluorooctanoic acid (PFOA), 6:2Cl-PFAES and 8:2Cl-PFAES at concentrations up to 100 mu g/L can significantly enhance the RP4 plasmid-mediated conjugative transfer of antibiotic resistance genes (ARGs) within and across genera as much as 3.38-fold. Perfluorooctanoic acid (PFOA), a representative PFAS, was then selected to investigate the related mechanisms within genera by which PFAS promoted the conjugative transfer of ARGs. The phenotypic experiments demonstrated that PFOA could induce oxidative stress, enhance cell membrane permeability and promote the excretion of extracellular polymeric substances in Escherichia coli, resulting in the elevation of intercellular contact and conjugative transfer of ARGs. Moreover, quantitative polymerase chain reaction revealed that PFOA exposure regulated the expression of conjugation-related genes. In addition, PFOA has also been shown to alter microbial metabolic pathways, including amino acid metabolism, nucleotide metabolism, and membrane translocation, thus altering cellular energy allocation to influence the conjugative transfer of ARGs. This study deepened the understanding of PFAS in promoting the propagation of ARGs, hence improving awareness of the ecological and health risks of PFAS.