Microplastics as vectors for the spread of antibiotic resistance genes across aquatic ecosystems: microbial adaptation and temporal dynamics

Microplastics (MPs) carrying biofilms can travel across different aquatic ecosystems, representing an emerging route for the spread of antibiotic resistance genes (ARGs). However, this process remains poorly understood. In this study, the temporal dynamics of microbial communities and ARGs were examined in both biofilms and the surrounding water after MPs migrated from Taihu Lake into the Liangxi River, its outflow river, over a period of 1 to 5 weeks, during which 102 new ARG subtypes were detected. During the initial phase after migration, microbes and ARGs gradually diffused from the biofilm into the water, resulting in increasingly similar compositional profiles between the two habitats. Subsequently, however, microbial communities and ARGs in the biofilm and water began to diverge due to differing environmental conditions. Notably, shifts in microbial composition and ARG abundance were not synchronized—ARGs demonstrated greater temporal stability. Microbial communities in the receiving water adapted to MP stress by regulating genes related to RNA synthesis, cell membrane function, and sugar metabolism. Furthermore, quorum-sensing analysis indicated that these communities maintained ecological balance through dynamic adjustment of autoinducer levels, which followed a pattern of initial increase, subsequent decline, and eventual stabilization. These findings underscore the environmental significance of MP transport in shaping microbial and ARG dynamics across interconnected freshwater ecosystems.