Microbial and genetic responses of anammox process to the successive exposure of different antibiotics

The issues of antibiotics and corresponding resistance genes (ARGs) have attracted public attention due to their environmental destructiveness. Herein, the response of the anammox process to the typical antibiotics streptomycin (STM) and spiramycin (SPM) was systematically explored. In terms of process performance, the anammox system was highly resistant to STM (50 mg L-1), while 3 mg L-1 SPM led to a significant inhibition. Exposure to STM resulted in the selective cultivation of Candidatus Kuenenia, while SPM significantly reduced its abundance. In addition, the relative abundance of bacteria belonging to Chloroflexi increased significantly during the SPM feeding phase, implying its potential resistance. The intI1 and corresponding ARGs (STM resistance genes: aadA, aadB, and aph3ib; SPM resistance genes: ereA, ermF and mphA) generally increased under stress from antibiotics. Co-occurrence network analysis showed that the collaboration among multiple ARGs might be the strategy used to relieve STM stress in the anammox system. This study systematically revealed the response of the anammox process to successive exposure to STM and SPM, and provides guidance for the treatment of wastewater multiple antibiotics containing.