Response of Anammox biofilm to antibiotics in trace concentration: Microbial activity, diversity and antibiotic resistance genes.

Long-term impacts of two antibiotics-norfloxacin (NOR) and erythromycin (ERY) in trace concentration (1ug L-1) on Anammox biofilm were investigated. The specific Anammox activity (SAA) and dehydrogenase activity (DHA) of Anammox biofilm were detected by batch experiments, the microbial diversity was analyzed using high-throughput sequencing technology and the antibiotic resistance genes (ARGs) were measured by qPCR. Results showed that long-term NOR feeding decreased 30% SAA and 39.6% DHA, and also decreased the abundance of the OTUs related to autotrophic nitrogen removal, while ERY had slight impact on Anammox. Only two ARGs targeted to ERY (ermB, mphA) were detected in the two Anammox systems while those targeted to NOR (qnrA, qnrB, qnrD, and qnrS) were not detected. The relative expression of ermB to 16S rRNA increased from 2.08±0.32×10-4 to 3.53±1.18×10-4, and that of mphA increased to 5.00±0.48×10-4 from 4.48±1.32×10-5. The induced ARGs in the Anammox system help it resist the ERY shock.