Nanoplastics promote the dissemination of antibiotic resistance genes and diversify their bacterial hosts in soil

The wide application of plastics has led to the ubiquitous presence of nanoplastics and microplastics in terrestrial environments. However, few studies have focused on the mechanism underlying the effects of plastic particles on soil microbiomes and resistomes, especially the differences between nanoplastics and microplastics. This study investigated the microbiome and resistome in soil exposed to polystyrene microplastics (mPS) or nanoplastics (nPS) through 16S rRNA and shotgun metagenomic sequencing. Distinct microbial communities were observed between mPS and nPS exposure groups, and nPS exposure significantly changed the bacterial composition even at the lowest amended rate (0.01%, w/w). The abundance of antibiotic resistance genes (ARGs) in nPS exposure (1%) was 0.26 copies per cell, significantly higher than that in control (0.21 copies per cell) and mPS exposure groups (0.21 copies per cell). It was observed that nanoplastics, bacterial community, and mobile genetic elements (MGEs) directly affected the ARG abundance in nPS exposure groups, while in mPS exposure groups, only MGEs directly induced the change of ARGs.