Photoaging microplastics as ecological architects of antibiotic resistance dissemination in aquatic sediments: Shifting bacterial adaptation from metabolic regulation to invasive phenotypes

Microplastics (MPs) are widely present in aquatic environments and serve as carriers, facilitating the migration and dissemination of antibiotic resistance genes (ARGs), which pose significant threat to ecosystem stability and human health. This study conducted continuous observations in natural sediment environments to systematically evaluate the impact of photoaging of polyethylene (PE) and polylactic acid (PLA) on the antibiotics resistance of sediments. With the increase in photoaging and cultivation time, the abundance of ARGs, virulence factor genes (VFGs), and mobile genetic elements (MGEs) in sediments also increased, especially after long-term exposure to aged PLA. The study further identified microbial adaptation strategies, including genetic-level alterations (e.g., regulation of cellular state), modifications in community structure (e.g., increases in specific microorganisms), and enrichment of metabolic pathways. Long-term exposure to MPs drove bacteria from adaptive metabolic regulation towards the evolution of invasive phenotypes. Furthermore, high-risk pathogenic bacteria were identified, and the SHAP model quantified factors influencing ARGs abundance, revealing that synergistic effects between MGEs and VFGs drive ARGs proliferation. In summary, these findings reveal a mechanism by which photoaged microplastics, particularly biodegradable PLA, remodel the sediment microbial resistome by shifting bacterial adaptation strategies and fostering synergistic interactions between MGEs and VFGs, thereby amplifying the ecological and health risks associated with antibiotic resistance.