Polyethylene microplastics specifically drive the dissemination of ARGs: Mechanisms involving microbial community restructuring and horizontal gene transfer

As emerging contaminants, the impact of microplastics (MPs) on antibiotic resistance genes (ARGs), virulence factors (VFs), and host microbial communities in lakes remains unclear. To address this, we conducted a 28-day incubation experiment using water from Yiquan Lake, employing metagenomic sequencing to investigate the effects of different types of microplastics-polyethylene (PE), polystyrene (PS), polypropylene (PP), and a mixture (Mix), each at a concentration of 1 item/L-compared to a raw water control (RAW). Results showed significant enrichment of Proteobacteria and Bacteroidetes in PE and Mix groups. Genera such as Agrobacterium and Microbacterium increased in PE and PS groups, serving as major hosts of ARGs and VFs. Network analysis revealed positive correlations between Agrobacterium, Escherichia, and ARGs, suggesting horizontal gene transfer may facilitate the spread of resistance and virulence. Two-factor PS formed highly connected yet competitive networks, whereas Mix constructed modular and stable networks. Single-factor PE enhanced microbial connectivity but reduced ARGs connectivity, while Mix increased the modularity of both microbes and ARGs. PE elevated the abundance of ARGs, VFs, and mobile genetic elements, with multidrug resistance and efflux pumps as dominant mechanisms. Additionally, PE downregulated quorum sensing transporter genes while upregulating regulatory factors, significantly promoting RND efflux systems (AcrAB-TolC) to maintain resistome homeostasis. This study highlights the distinct environmental effects of different MPs, underscoring the need to prioritize PE-related risks in aquatic ecosystems. Improved management of plastic waste in and around lakes is recommended to mitigate MP-mediated ARG dissemination and preserve freshwater ecosystem services.