Fate and abundance of antibiotic resistance genes on microplastics in facility vegetable soil

Microplastics (MPs) and antibiotic resistance genes (ARGs) coexist widely in farmland soils, but the fate and abundance of ARGs on MPs is rarely explored. In this study, high-throughput fluorescent quantitative polymerase chain reaction was used to determine ARGs on MPs in facility vegetable soil. The results indicated that when the particle size of the MPs was larger, the weathering was more serious, or the MPs came from soils with a long vegetable cultivation period, the levels of antibiotics and heavy metals on the MPs were higher. The distribution of the detected ARGs types on distinct MPs showed changes. Compared with weakly weathered MPs, the detected beta lactamase and aminoglycoside resistance genes on strongly weathered MPs were decreased by 2.6% and 1.7%, while the detected sul-ARGs and Macrolide-Lincosamide-Streptogramin B (MLSB) resistance genes were increased by 1.5% and 2.8%. Compared with smaller MPs, the detected MLSB and vancomycin resistance genes on larger MPs were decreased by 2.0% and 1.4%, while the detected fluoroquinolone, quinolone, florfenicol, chloramphenicol, and amphenicol (FCA) resistance genes and sul-ARGs were increased by 1.2% and 1.0%. Compared with MPs in soil after three years of vegetable cultivation, the detected FCA resistance genes and sul-ARGs on MPs in soil after ten years of vegetable cultivation were decreased by 1.3% and 1.6%, while the detected beta lactamase and aminoglycoside resistance genes were increased by 1.0% and 1.7%. This study suggests that MPs with larger size, stronger weathering or from soil after long-term vegetable cultivation adsorb more antibiotics and heavy metals and cause more mobile genetic elements, which can contribute to antibiotic resistance on the MPs.