Roles of micro/nanoplastics in the spread of antimicrobial resistance through conjugative gene transfer

Micro- and nanoplastics (M/NPs) can facilitate the transfer of antimicrobial resistance genes (ARGs) between bacteria. Using Escherichia coli and Enterococcus faecalis as model donors and recipients, this study shows that ARG transfer occurs more frequently within the same genus than between genera. Polystyrene (PS) particles of 20 and 120 nm broadly enhance conjugation, while 1-µm PS selectively promotes ARG transfer to E. coli and alters the expression of conjugation- and pili-related genes. Importantly, even environmentally relevant PS concentrations (0.1 mg/L) increase ARG transfer, coinciding with elevated reactive oxygen species, ATP levels, and membrane permeability in both donor and recipient cells. Overall, the findings indicate that M/NPs can promote AMR dissemination in aquatic environments and represent a potential ecological risk.