Dual roles of polystyrene nanoplastics in reshaping antibiotic resistance genes dynamics in soil-plant systems: Highlighting shifts in specific hosts and functions.

The proliferation of nanoplastics in agroecosystems raises concerns about their role in disseminating antibiotic resistance genes (ARGs) through soil-plant systems. This study investigated the dynamics and underlying mechanisms of ARGs translocation in a soil-pakchoi system under polystyrene nanoplastic (PS NPs) exposure. In soil, PS NPs elevated ARGs abundance by 11.68-18.61 % while hindering their transfer into root tissues. PS NPs stimulated a marked proliferation of key pathogenic ARGs-carrying taxa in soil, including Mycobacterium tuberculosis and Pectobacterium atrosepticum. The activation of critical ARGs-related pathways (biofilm formation, membrane transport systems, and SOS responses) by PS NPs may further contribute to soil ARGs dissemination. Conversely, within plant tissues, PS NPs reduced ARGs diversity by 11.24-27.98 % despite enhancing the translocation of ARGs from the stems to the leaves. This shift was driven by a suppression of pathogenic ARGs hosts and ARGs-related functional pathways in roots, accompanied by a 54.08 % enrichment of the beneficial antagonist Lysobacter. Health risk assessment indicated that PS NPs amplified ARGs-associated hazards in soil (73.84-234.72 %) but mitigated in plant tissues (33.18-86.56 %). These findings highlighted the dual role of PS NPs in shaping ARGs dynamics: exacerbating soil resistome risks while offsetting translocation to edible plants.