Spatiotemporal transmission mechanisms of resistance genes in the Chishui River: Perspectives from environmental drivers and microbial interactions

The accelerating spread of antimicrobial resistance in natural ecosystems, driven principally by the dissemination of antibiotic resistance genes (ARGs), represents an escalating challenge for both environmental integrity and public health security. Aquatic systems contaminated with ARGs alongside associated virulence factors (VFs) and metal resistance elements (MRGs) have emerged as critical reservoirs of resistance propagation. This study employed metagenomic approaches to analyze microbial communities and functional diversity in the Chishui River, which spans three distinct regions under significant anthropogenic influence. The results revealed that microbial communities exhibit distinct spatiotemporal variations predominantly governed by temperature, DO, TP, and TN. In addition, variations in land use types across different regions also directly shaped microbial diversity patterns, subsequently exerting direct and indirect effects on mobile genetic elements (MGEs), ARGs, and VFs, ultimately leading to the enrichment and dissemination of high-risk resistance genes. Both microbial communities and ARGs exhibited short-distance migration patterns. Notably, a synergistic covariation pattern was observed between antibiotic resistance genes (ARGs) and dissimilatory nitrate reduction to ammonium (DNRA) functional genes, indicating a potential ecological linkage between these two genetic traits. A total of 138 metagenome-assembled genomes have been identified as potential vectors for ARG dissemination. We further revealed a novel synergistic link between ARG abundance and the DNRA process, and the class Gammaproteobacteria was identified as the primary vector of resistance dissemination, functioning as dominant co-hosts for ARGs, MRGs, VFs, and DNRA genes in the Chishui River. These findings offer new insights into river ecosystems, underscoring the importance of monitoring the fate of ARGs to enhance our understanding of how river ecosystems respond to human activities.