Response of denitrifying community, denitrification genes and antibiotic resistance genes to oxytetracycline stress in polycaprolactone supported solid-phase denitrification reactor.

The coexistence of nitrate and antibiotics in wastewater is a common problem. The study aimed to explore the response of denitrifying community, denitrification genes and antibiotic resistance genes (ARGs) to oxytetracycline (OTC) stress in polycaprolactone (PCL) supported solid-phase denitrification (SPD) reactors. Complete nitrate reduction (greater than99%) was achieved in SPD system with OTC stress of 0, 0.05, 0.25 and 1 mg L during three-month operation, while it significantly declined by about 5% at a further increased OTC level of 5 mg L. The efficient denitrification strongly related with a rich diversity of denitrifiers, while the abundances of which dramatically reduced as the OTC concentration reached ≥0.25 mg L, which caused significant decline of denitrification genes, especially for narH, narJ, narI nirD, nosZ, and norB. Tetracycline resistance genes were a major type of promoted ARGs by different OTC stress, mainly related with the increase of tet36, tetG, tetA, tetM and tetC.