Influence of Ciprofloxacin on the Microbial Community and Antibiotics Resistance Genes in a Membrane Bioreactor

Abstract

A membrane bioreactor (MBR) was used to treat ciprofloxacin (CIP)-contaminated artificial wastewater. The microbial community structure and the abundance of antibiotic resistant genes (ARGs) in the MBR were studied at four CIP dosages (0, 5 mg·L-1, 10 mg·L-1, and 15 mg·L-1). The results showed that Proteobacteria and Bacteroidetes remained the dominant phylum, with relative abundances of 57.5% and 12.7%, respectively, as the dosage of CIP was increased from 0 mg·L-1 to 15 mg·L-1. Rhodocyclaceae, Chitinophagaceae, and Comamonadaceae became the dominant family with abundances of 29.96%, 5.44%, and 6.60%, respectively. Methyloversatilis, Ferruginibacter, Zoogloea, and Comamonas became the dominant genus, with relative abundances of 21.70%, 7.56%, 5.24%, and 4.15%, respectively. The decrease of Chao1, ACE, and Shannon and the increase of Simpson indicated a decrease in microbial abundance and diversity. The relative abundances of Nitrosomonas, Nitrospira, Alcaligenes, and Nitrobacter decreased, which caused a decrease in the NH3-N removal rate. A CIP-ARGs analysis revealed that the relative abundances of gyrA, gyrB, and parC were increased, beginning after the sludge was dosed with 5 mg·L-1of CIP for 33 days, which augmented the risk for microbial drug-resistance.