Distribution of Antibiotic Resistance Genes and Their Associations with Bacterial Communities and Water Quality in Freshwater Lakes

Urban lakes of smaller size are affected by various human recreational activities and pollution sources. Few studies focused on the relationship between resistance genes and bacterial communities in freshwater lakes. In this study, we investigated the prevalence of ten antibiotic resistance genes (ARGs), bacterial composition, and the physicochemical parameters of three smaller urban freshwater lakes in Nanjing, China. The three lakes were highly eutrophic as their total nitrogen (TN), total phosphorous (TP), chemical oxygen demand, and chlorophyll a (Chl a ) values exceeded Chinese water quality standards. The spatial distribution of ARGs varied in the three lakes, with sul2 (13 log 10 gene copies/100 mL) as the dominant, followed by strA (13 log 10 gene copies/100 mL) and sul1 (13 log 10 gene copies/100 mL). vanA was the most dominant in Zixia, sul1 was the most dominant in Nan, and sul2 in Xuanwu freshwater lake. The dominant phyla groups among the three lakes were Proteobacteria, Actinobacteria, Bacteroides, and Cyanobacteria. We found that pH positively correlated with sul1 (0.829*) and sul2 (0.943**) genes and physicochemical parameters such as TN, NH 4 -N, TP, and Chl a had a similar relationship with ARGs, thus further providing insight into the physicochemical parameters that could directly or indirectly influence ARG dissemination. Cyanobacteria and Firmicutes were significantly correlated with tetG , while Chloroflexi was significantly correlated with ermB , suggesting their potential influence on ARG propagation. Our findings indicate that urban freshwater lakes are severely polluted, with certain physicochemical factors indirectly aiding in ARG propagation, and bacterial communities could potentially contribute to ARG spread, which could be a significant health concern.