Distribution and Influence on the Microbial Ecological Relationship of Antibiotic Resistance Genes in Soil at a Watershed Scale

Antibiotic resistance genes (ARGs) are ubiquitous in the environment, with previous studies mainly focusing on the terrestrial ecosystem, which is prone to higher antibiotic application. However, the characteristics, distribution pattern, and driving factors of soil ARGs at the macro scale are still unclear. In this study, the soil ARGs, antibiotics, mobile genetic elements (MGEs), soil properties, toxic metals, polycyclic aromatic hydrocarbons (PAHs), and bacterial community in the Taipu River Basin were analyzed to investigate the distribution and dissemination of ARGs at a watershed scale. The results revealed that ARGs were widespread in the soils along the Taipu River, and that ARG profiles varied greatly with different types of land use, but showed regional similarities. The characteristics were mainly determined by antibiotic input and the ARG transmission mediated by MGEs. The order of the contribution of environmental factors to ARG distribution was toxic metals > PAHs > soil properties. Toxic metal pollution was coupled with ARGs through MGE mediation, while PAHs and soil properties were most likely to affect the ARG distribution by shifting the bacterial community. The microbial-ecological relationship changed significantly with the enrichment of ARGs, and its impact may extend to the watershed scale. Transposon IS1247 can be used as an indicator of the ARGs impact on the microbial ecological relationship in the soils of the Taipu River Basin.