Comparison of Microbiomes and Resistomes in Two Karst Groundwater Sites in Chongqing, China.

Karst groundwater is an important water resource, as it accounts for about 15% of the total landscape of the earth and supplies 20% of potable water worldwide. The antibiotics resistance is an emerging global concern, and antibiotics residual and increase of antibiotic resistance genes represent serious global concerns and emerging pollutants. There is no report on the antibiotic resistance genes in groundwater. To survey resistome and microbiome in karst groundwater, two karst water samples were chosen for metagenome and metatranscriptome study, namely the 37 spring (C) and Dongcao spring (R) in Beibei, Chongqing, China. The two sites differ significantly in sulfur content, geochemical parameters, community structure, antibiotic resistance genes, and mechanisms, and these results may be influenced by anthropogenic activities. Combining with the Antibiotic Resistance Genes Database, three types of resistance genes baca, sul2, sul1 are present in R and C, and ant3ia, ermc, tetpa are also present in R. The number of all resistance genes in R was more than C, and Proteobacteria, Bacteroidetes, Nitrospirae are the main sources of antibiotic resistance genes. In addition, a large number of genes related to antibiotic gene transmission and drug resistance were found in both samples. Karst groundwater is an important source of drinking water and a possible venue for the transmission of microbial antibiotic resistance genes. However, few studies addressed this issue in karst groundwater, despite its widespread and great importance to global ecosystem. Karst groundwater is a reservoir for antibiotic resistant genes, and measures to control these resistant genes are urgently needed.