Antibiotic resistance genes are closely linked with bacterial functions during anoxic-oxic treatment process of pig wastewater

The distribution of antibiotic resistance genes (ARGs) during the anoxic-oxic (A/O) treatment process of pig wastewater was studied by metagenomics. Subsequently, the relationships among bacterial communities, functions and ARGs were analyzed. During the A/O treatment processes, 314 ARG subtypes belonging to 15 ARG types were detected. The dominant ARG types were multidrug, MLS, peptide, glycopeptide, beta-lactam, aminoglycoside and tetracycline resistance genes. The resistance genes MexS, oleC, tetA(48), rphB, macB and smeS can be used as index factors to predict the total abundance of ARGs by a linear function. The functional bacterial genera and genes involved in C-, N- and S-cycling had significant positive correlations with some ARGs, suggesting that functional bacteria were potential ARG hosts. In addition, network analysis suggested that OprM was positively correlated with carbon and nitrogen metabolism. Presumably, functional bacteria containing ARGs may protect the removal process of pollutants in pig farm wastewater. This study highlighted the profiles of ARGs in pig farm wastewater A/O treatment processes and their complex interactions with bacterial functions, and provided an important reference for resolving the contradiction between pollutant removal and antibiotic resistance prevention and control in pig farm wastewater.