Effects and Mechanisms of Polystyrene Micro- and Nano-Plastics on the Spread of Antibiotic Resistance Genes from Soil to Lettuce.

Effects of microplastics (MPs) and nanoplastics (NPs) on the spread of antibiotic resistance genes (ARGs) in soil -plant systems are still unclear. To investigate the spread and mechanisms of ARGs from soil to lettuce, lettuce was exposed to soil spiked with two environmentally relevant concentrations of polystyrene MPs (100 mu m) and NPs (100 nm). Results showed that microorganisms that carried ARGs in soil were increased after exposure to MPs/ NPs, which led to an increase in ARGs in roots. NPs were absorbed by roots and can be transported to leaves. Analysis of transcriptomics, proteomics and metabolomics indicated that high concentration of NPs regulated the expression of related genes and proteins and improved the accumulation of flavonoids in the lettuce, therefore decreased the abundance of microorganisms that contained ARGs. Our work emphasizes the size and dose in-fluences of MPs and NPs on the spread of ARGs from soil to plant.