Selective enrichment of antibiotic resistance genes and pathogens on polystyrene microplastics in landfill leachate

Landfill leachate is an important reservoir of antibiotic resistance genes (ARGs) and microplastics (MPs). However, the enrichment characteristics of ARGs on MPs and the effect of MPs' presence on ARGs in surrounding leachates are little studied. Therefore, we investigated the differences of ARGs, mobile genetic elements (MGEs), bacterial communities and pathogens on polystyrene MPs, in MPs-surrounding leachate and in control (leachate with the absence ofMPs). The results revealed that ARGs were selectively enriched onMPs, which was similar in three types of leachate environments. The genes strB and blaTEM were maximally enriched and mefA, ermB, tetM and tetQ were slightly enriched on MPs, and the degree of ARGs enrichment increased with time during the 60 days of the experiment. Furthermore, compared to the leachate, MPswere observed to have the higher abundances of MGEs and distinct bacterial communities, both of which were closely associated with ARGs on MPs. Pathogens were distinct and more abundant on MPs compared to that in leachate, and 11 pathogens were identified as potential hosts for ARGs on MPs. Additionally, the presence of MPs (500 mg/L) induced few changes in ARGs' abundances, MGEs' abundances and bacterial communities in MP-surrounding leachate within 60 days. Overall, this study suggested that MPs could selectively enrich ARGs and pathogens from the surrounding environments, which promoted the understanding of the combined pollution properties of MPs and ARGs. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study found that antibiotic resistance genes (ARGs) on polystyrene microplastics (MPs) were selectively enriched, closely associated with MPs, and pathogens in the surrounding environment were also enriched on MPs. The presence of MPs did not significantly affect the abundances of ARGs, MGEs, and bacterial communities in the surrounding leachate within 60 days.