Effects of antibiotics and heavy metals on ARGs in Danjiangkou Reservoir

Antibiotic resistance genes (ARGs) have attracted more and more attention due to their potential exposure hazards. The Danjiangkou Reservoir (DJKR) is the source of water for the Middle Route Project under the South-to-North Water Transfer Scheme in China. To clarify the distribution of ARGs and their influencing factors in DJKR (including Danjiang Reservoir (DR) and Hanjiang River Reservoir (HR)), we used metagenomic analysis to investigate the ARGs. The results showed that the most abundant bacteria of both parts were Proteobacteteria. Antibiotic efflux (58.2 %) and alteration of antibiotic targets (69.4 %) were the main mechanisms in DR and HR. The composition of ARG species was similar in the two parts, but the number of ARG isoforms in HR was significantly higher than that in DR. ARG Intl1 was detected in both DR and HR. Network analysis showed a significant correlation between mobile genetic elements (MGEs) and ARGs. Heavy metals also showed a significant correlation with ARGs. Interestingly, the relationship between heavy metals and ARGs were more significant than that between antibiotics and ARGs.