Insight into the microbial and genetic response of anammox biomass to broad range concentrations of different antibiotics: Linking performance and mechanism

•The response of the anammox process to CIP and CLA was revealed for the first time.•The anammox process had higher OTC and CIP tolerance than CLA.•Candidatus Jettenia included ARGs targeted CLA.•The synergistic effect of EPSs and ARGs reduces the harmful effects of antibiotics. Antibiotics have become emerging pollutants occurring in wastewater, influencing the activity of microorganisms responsible for wastewater treatment. Moreover, the potential application of the anammox process in the treatment of antibiotic-containing wastewater has paid much attention. A common antibiotic, OTC (oxytetracycline), CIP (ciprofloxacin), and CLA (clarithromycin) are recognized to be monitored in wastewater due to their relatively high concentration and hazardous impact on the environment. However, their effect on the anammox process remains unknown. Therefore, this paper presents the study concerning the long-term effects of a successive concentration of three antibiotics (OTC, CIP, CLA) on the anammox process, with special emphasis on treatment efficiency, resistance mechanism, bacteria cell morphology, and activated sludge community structure. It is worth noting that the influence of a successive concentration of CIP and CLA has been studied for the first time. Results revealed that anammox community could adapt to CIP, OTC, and CLA at low concentrations (