Microplastics as vectors for microbial pollutants: Biofilm-associated transfer of pathogens and antibiotic resistance genes in zebrafish intestine.
As composite carriers of microorganisms and pollutants, biofilm-attached microplastics (MPs) serve as potential vectors for the environmental migration and biotransmission of antibiotic resistance genes (ARGs) and pathogens. In this study, traditional polypropylene (PP) and biodegradable polylactic acid (PLA) MPs were used to investigate the interference effects of biofilms-attached MPs on gut microbiota and ARGs transmission, through a combination of laboratory biofilm cultivation, zebrafish (Danio rerio) exposure simulations, metagenomic sequencing, and metabolomic profiling. Results showed that MP biofilms likely induced gut dysbiosis and were associated with altered diversity and abundance of pathogens and ARGs. At the phylum level, Nitrospira was transferred from PP biofilms to the gut. At the genus level, 23 genera were transferred from MP biofilms, with PLA (23 genera) showing higher transfer capacity than PP (4 genera). Notably, two human pathogens, one opportunistic pathogen, and two ARGs (adeF and oqxB) were specifically transferred from PLA biofilms, highlighting the unique dissemination risk of biodegradable MPs. Mechanistically, MPs may activate mobile genetic elements (e.g., Tn916 transposon) through metabolic remodeling and quorum sensing, thereby promoting horizontal gene transfer and ARGs dissemination within the gut. Our findings highlight the potential role of MPs as carriers of microorganisms and ARGs, underscoring the biotransmission risks of antibiotic resistance caused by composite pollution.