[Microplastic-Induced Alterations to Antibiotic Resistance Genes in Seawater]

The increasing and combined pollution of microplastics (MPs) and antibiotic resistance genes (ARGs) in aquatic environments is a great ecological and health concern. However, MP-induced alterations to ARGs in seawater is poorly understood, impeding risk assessment of plastics. We profiled the diversity and abundance of ARGs and mobile genetic elements (MGEs) in seawater after the addition of three different MPs (PE, PVC, and PVA) and 49-day aerated incubation.A total of 20, 35, 42, and 64 ARGs were detected in BLK, PE, PVC, and PVA, with 2, 4, 2, and 3 MGEs, respectively. The absolute abundance of ARGs in the seawater aerated with MPs ranged from 4.01×10⁶ copies ·L^-1 to 1.05×10⁸ copies ·L^-1. Additionally, the variety and richness of ARGs and MGEs in PVA were significantly higher than in the original seawater, or the seawater aerated with the other two MPs. This indicates that PVA, which is water soluble, could induce more diverse and abundant ARGs in seawater. Significant correlations among ARGs, MGEs, and 16S rRNA genes were observed, implying that the occurrence of MGEs in seawater may accelerate the transmission of ARGs through horizontal gene transfer, and bacterial microorganisms could directly affect the propagation and dissemination of ARGs.