Tracking antibiotic resistance genes in microplastic-contaminated soil.

Agricultural soils and microplastics (MPs) are hotspots for antibiotic resistance genes (ARGs). Plastic mulch is the most important source of MPs in agricultural soil. ARGs, mobile genetic elements (MGEs), and their host profiles in long-term mulch MP-exposed soils remain unclear. In the present study, metagenomics was used to investigate the distribution patterns of ARGs and MGEs in eight Chinese provinces with a long history of plastic mulch use. A total of 204 subtypes of ARGs and thousands of MGEs (14 integrons, 28 insertions, and 2993 plasmids) were identified. A similar diversity of ARGs was found among MPs film-contaminated sites. The types of ARGs with a high abundance were more concentrated, and multidrug resistance genes were the dominant ARGs. Soils from regions with a longer history of plastic film use (such as Xinjiang province) had a higher abundance of ARGs and MGEs. The distribution of ARGs and MGEs exhibited a modular network distribution pattern. A total of 27 ARG subtypes and 29 MGEs showed co-occurrence network relationships. More than 10 common hosts of ARGs and MGEs, such as Pseudomonas, were found, and their abundances were highest in three provinces, including Xinjiang. This study may help elucidate the impact mechanism of long-term MP residues on the occurrence and spread of ARGs in soil.