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

The role of micro/nanoplastics (M/NPs) in the dissemination of antimicrobial resistance (AMR) remains insufficiently understood. Here, we examine how polystyrene (PS) M/NPs of varying sizes and concentrations affect AMR gene (ARG) transfer in model systems with gram-negative (Escherichia coli) and gram-positive (Enterococcus faecalis) donors. In these systems, the ARG transfer frequency is higher for intrageneric pairs than for intergeneric pairs. The 20- and 120-nm-sized PS broadly facilitate conjugation, whereas the 1-μm-sized PS selectively promotes ARG transfer to E. coli recipients, in addition to altering the expression of conjugation- and pili-associated genes. Notably, an environmentally relevant (0.1 mg/L) concentration of PS M/NPs facilitates AMR transfer in the tested systems, which correlates with increased reactive oxygen species levels, ATP levels, and cell membrane permeability in both donors and recipients. Collectively, our findings underscore the role of M/NPs in facilitating AMR spread in specific bacterial systems, providing valuable insights for understanding their potential ecological risk in water environments.