The impact of microcystin on antibiotic resistance genes and microbial communities in Yangtze River sediments

The escalating of water pollution associated with microcystins (MCs) and antibiotic resistance genes (ARGs) poses a significant environmental challenge. As one of China's most crucial water systems, the Yangtze River's ecological health is not only vital for regional ecosystems but also carries global environmental significance. While the concentration of MCs detected in the Yangtze River sediments is moderate, the impact of exogenous MCs on ARGs and microbial communities within these sediments remains poorly understood. This study examines 18 sediment samples collected from six regions along the upper, middle, and lower reaches of the Yangtze River. By introducing exogenous MCs, we analyzed the responses of the sulfonamide resistance gene (<i>sul</i>1), tetracycline resistance gene (<i>tet</i>A), integron gene (<i>intI</i>1), and the microbial community composition. The results indicate that exogenous MC inputs significantly affect the abundance of ARGs in the sediments, with <i>sul</i>1, <i>tet</i>A, and <i>intI</i>1 exhibiting a general increasing trend. However, the microbial community structure was not substantially affected by the MCs, with regional differences exerting a greater influence on microbial composition than the exogenous MCs input. Proteobacteria, Bacteroidetes, Acidobacteria, and Chloroflexi were the dominant phyla in the Yangtze River sediments. The introduction of exogenous MCs may increase the environmental risk of ARG dissemination. These findings enhance our understanding of how MCs affect ARG dissemination and microbial community structures in the Yangtze River ecosystem.