Co-exposure of microplastics and sulfamethoxazole propagated antibiotic resistance genes in sediments by regulating the microbial carbon metabolism

The concerns on the carriers of microplastics (MPs) on co-existing pollutants in aquatic environments are sharply rising in recent years. However, little is known about their interactions on the colonization of microbiota, especially for the spread of pathogens and antibiotic resistance genes (ARGs). Therefore, this study aimed to investigate the influences on the propagation of ARGs in sediments by the co-exposure of different MPs and sulfamethoxazole (SMX). The results showed that the presence of MPs significantly enhanced the contents of total organic carbon, while having no effects on the removal of SMX in sediments. Exposure to SMX and MPs obviously activated the microbial carbon utilization capacities based on the BIOLOG method. The propagation of ARGs in sediments was activated by SMX, which was further promoted by the presence of polylactic acid (PLA) MPs, but significantly lowered by the co-exposed polyethylene (PE) MPs. This apparent difference may be attributed to the distinct influence on the antibiotic efflux pumps of two MPs. Moreover, the propagation of ARGs may be also dominated by microbial carbon metabolism in sediments, especially through regulating the carbon sources of carboxylic acids, carbohydrates, and amino acids. This study provides new insights into the carrier effects of MPs in sediments. The spread of antibiotic resistance genes (ARGs) is a growing public health issue worldwide, which may be enhanced by the presence of antibiotics and microplastics (MPs). As the carriers of co-existing antibiotics, MPs may further alter the behavior of these pollutants. However, their interactions on the ARGs spread are still largely unknown. Herein, we investigated the effects on the propagation of ARGs in sediments of co-exposure to MPs and antibiotic sulfamethoxazole (SMX). The results revealed that both SMX and MPs could alter the propagation of ARGs in sediments through interfering with the microbial carbon metabolism. This finding provides a new insight into the propagation risks of ARGs under increasing global MPs pollution.