Composition of norfloxacin-resistant bacteria and isolation of norfloxacin-degrading bacteria in subtropical aquaculture ponds in China

To analyze the composition of norfloxacin-resistant bacteria and norfloxacin-degrading bacteria in pond water and sediment in subtropical China, the composition of antibiotic resistant bacteria in pond water and sediment enriched with norfloxacin-containing medium was analyzed by high-throughput sequencing. Sediment and water samples were collected from 3 fish ponds in subtropical China, and domesticated with norfloxacin, subsequently norfloxacin-resistant bacteria through high-throughput sequencing of 16S rDNA, and isolated norfloxacin--degrading bacteria. Our results showed that the pond sediment and water contain a variety of norfloxacin-resistant bacteria, mainly from Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes, and Chloroflexi. Moreover, we isolated two norfloxacin-degrading bacteria (NorXu-2 and NorXu-3). The norfloxacin-degrading rate by NorXu-2 and NorXu-3 in the culture mediums with 200 μg/mL was the highest, which was up to 49.71% and 35.79%, respectively. When the norfloxacin concentration was 200 μg/mL, NorXu-2 and NorXu-3 had the best norfloxacin- -degrading effect at pH of 6, and the degradation rates were 53.64% and 45.54%, respectively. Moreover, NorXu-3 exhibited a good tolerance to high NaCl concentration. These results not only provided basic data for the follow-up study of the molecular mechanism of antimicrobial microbial degradation, but also provided potential norfloxacin degrading bacteria for norfloxacin removal and bioremediation in aquaculture environment.