[Distribution， Diffusion Regularity， and Influencing Factors of Antibiotic Resistance Genes in the Water Transfer Chain from Luanhe River to Tianjin Based on Metagenomics].

Yuqiao Reservoir is an important drinking water source for Tianjin. As the source of the "Water Diversion Project from Luanhe River to Tianjin"， there are more than one hundred types of contamination of antibiotic resistance genes （ARGs） in the Panjiakou and Daheiting Reservoirs. However， the level of ARGs in the upstream water transfer chain of Yuqiao Reservoir （Linhe River， Shahe River， and Lihe River） has not yet been studied. It is necessary to characterize the dynamic mechanism of ARGs in this basin to gain a deeper understanding of water ecosystem security. In this study， metagenomic methods were used to investigate the distribution characteristics of ARGs and mobile genetic elements （MGEs） in the surface water of the water transfer chain from Luanhe River to Tianjin during different periods， combined with the correlation mechanisms among microbial community structure and environmental factors. The results showed that the water transfer chain of the Luan River to Tianjin contained 21 types of ARGs with 1 161 subtypes. The main types of ARGs were multidrug， macrolide-lincosamide-streptogramin b （MLSB）， and tetracycline， with macB and tetA58 being the dominant ARGs. The predominant types of MGEs were integration/excision （IE） and replication/recombination/repair （RRR）. Compared to that during the flood period， there was a significant positive correlation between ARGs and MGEs during the dry period. Correlation analysis indicated that temperature， dissolved oxygen， and nitrate showed significant correlation with various ARGs （P < 0.05）. The abundance of ARGs was more easily affected by multiple environmental factors， but the composition of ARGs showed correlations only with total phosphorus and dissolved total phosphorus. Proteobacteria was the most dominant phylum， and several dominant microbial genera， such as Acidovorax and Rhodoferax， also showed significant correlation with ARGs， especially during the dry period. The co-occurrence network analysis revealed the most significant co-occurrence relationship between ARGs and MGEs， and some microbial genera related to nutrient elements and photosynthesis also showed co-occurrence relationships with major ARGs. This project aims to profoundly understand the biogeochemical cycle mechanisms of ARGs in the upstream water transfer chain of the reservoir， and it can provide a scientific basis for decision-making to control the transmission of resistance genes within the regional basin.