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• Microbial and genetic responses of anammox process to ETC and SMZ were different. • The combined effects of ETC and SMZ was more significant than that of the single. • Increase in ARGs and EPS probably relieved the selection pressures of antibiotics. • Proteins in EPS provided binding sites for two antibiotics via hydrogen bonds. The anaerobic ammonium oxidation (anammox) process is regarded as a promising approach to treat antibiotic-containing wastewater. Therefore, it is urgent to elucidate the effects of various antibiotics on the anammox process. Moreover, the mechanism of extracellular polymeric substance (EPS) as protective barriers to relieve antibiotic stress remain unclear. Therefore, the single and combined effects of erythromycin (ETC) and sulfamethoxazole (SMZ), and interactions between EPS and antibiotics were investigated in this study. Based on a 228-day continuous flow experiment, high concentrations of ETC and SMZ had significant inhibitory effects on the nitrogen removal performance of the anammox process, with the abundances of corresponding antibiotic resistance genes (ARGs) increasing. In addition, the combined inhibitory effect of the two antibiotics on the anammox process was more significant and longer-lasting than that of the single. However, the anammox process was able to quickly recover from deterioration. The tolerance of anammox granules to the stress of low-concentration antibiotics was probably attributed to the increase in ARGs and secretion of EPS. Molecular docking simulation results showed that proteins in EPS could directly bind with SMZ and ETC at the sites of GLU-307, HYS-191, ASP-318 and THR-32, respectively. These findings improved our understanding of various antibiotic effects on the anammox process and the interaction mechanism between antibiotics and proteins in EPS. [Display omitted] [ABSTRACT FROM AUTHOR]

The feasibility of using anaerobic ammonium oxidation (anammox) process to treat wastewaters containing antibiotics and heavy metals was evaluated in this study. The nitrogen removal performance and characteristic parameters were monitored during the whole experimental period of 258 d. The single and joint effects of zinc and tetracycline on the microbial community were studied in upflow anaerobic sludge blanket (UASB) reactors. The anammox performance remained at levels comparable with the initial state at the lower inhibitor concentrations (zinc, 0–2.26 mg L−1; tetracycline, 0–0.5 mg L−1). When the concentrations of zinc and tetracycline increased to 3.39 mg L−1 in R 1 and 1.0 mg L−1 in R 2 , an obvious deterioration in performance was observed. Dual inhibitors with a total concentration of ≥3 mg L−1 caused dramatic decreases in the nitrogen removal efficiency of R 3. The quantification results showed that the abundances of eight antibiotic resistance genes (ARGs), czc A and int I1 in the experimental reactors generally increased under stress from metals or/and antibiotics, with final values higher than in the control, while the functional gene abundances were lower. Moreover, most genes exhibited significant correlations. Microbial community analysis indicated that Planctomycetes (represented by Candidatus Kuenenia) was inhibited by both zinc and tetracycline, but still held the dominant position. Furthermore, Caldilinea (belonging to Chloroflexi) maintained a higher abundance during the inhibitory period, implying its potential resistance to both inhibitors. These findings suggested that anammox could be inhibited by metals and antibiotics, but it has the potential to remove nitrogen from wastewaters containing both of them within the concentration threshold. • The inhibition thresholds of zinc and tetracycline on anammox were 3.39 and 1 mg L−1, respectively. • The joint inhibition of zinc and tetracycline on anammox was stronger than the single inhibition. • Caldilinea was the potential resistance bacteria. • Anammox has the potential to treat wastewaters containing small amounts of metals and antibiotics. [ABSTRACT FROM AUTHOR]

Antibiotics and antibiotic resistance genes (ARGs) have been recognized as emerging high-risk pollutants for human and animal health. This study systematically investigated the comprehensive effects of a typical antibiotic (sulfadimidine, SDM) in livestock and poultry breeding wastewater on the anammox process, with the aim of elucidating the intracellular and extracellular protective mechanisms of the anammox consortia to the antibiotic stress. Results revealed that the high-concentration SDM significantly reduced the specific anammox activity (SAA) by 37.8%. Changes in the abundance of Candidatus Kuenenia showed a similar trend with that of SAA, while other nitrogen-related microorganisms (e.g., Nitrosomonas and Nitrospira) contributed to the nitrogen removal especially during the inhibitory period. Resistance of the anammox consortia to SDM mainly depended on the protection of ARGs and EPS. Network analysis revealed the host range of eARGs was relatively larger than that of iARGs, and int I1 was closely associated with representative denitrifiers. In addition, metaproteomic analysis and molecular docking results indicated that abundant proteins in EPS could detain SDM in the extracellular matrix through forming complex via hydrogen bond. These findings provide a guidance for the stable operation of anammox process and ARGs transfer controlling. [Display omitted] • Exogenous 20 mg L−1 sulfadimidine (SDM) affected the anammox process performance. • Intracellular and extracellular protection depended on ARGs and EPS, respectively. • The absolute abundances of iARGs and eARGs increased under the stress of SDM. • Typical denitrifiers were the poteintal host of ARGs. • Extracellular proteins detained SDM through forming complex via hydrogen bond. [ABSTRACT FROM AUTHOR]

[Display omitted] • The response of anammox process to STM was revealed for the first time. • The anammox process had higher STM tolerance than SPM. • The int I1 and corresponding ARGs generally increased under stress from antibiotics. • The collaboration of ARGs implied the multiple resistance of anammox process. 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 int I1 and corresponding ARGs (STM resistance genes: aad A, aad B, and aph 3ib; SPM resistance genes: ere A, erm F and mph A) 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. [ABSTRACT FROM AUTHOR]

Antibiotic pollution is becoming increasingly severe due to its extensive use. The potential application of the anaerobic ammonium oxidation (anammox) process in the treatment of wastewater containing antibiotics has attracted much attention. As common antibiotics, spiramycin (SPM) and streptomycin (STM) are widely used to treat human and animal diseases. However, their combined effects on the anammox process remain unknown. Therefore, this study systematically evaluated the response of the anammox process to both antibiotics. The half maximal inhibitory concentrations of SPM and STM were determined. The continuous-flow anammox system could adapt to SPM and STM at low concentrations, while antibiotics at high concentrations exhibited inhibitory effects. When the concentrations reached 5 mg L−1 SPM and 50 mg L−1 STM, the nitrogen removal efficiency dramatically decreased and then rapidly recovered within 8 days. Correspondingly, the abundances of dominant bacteria and genes also changed with antibiotic concentrations. In general, the anammox process showed a stable performance and a high resistance to SPM and STM, suggesting that acclimatization by elevating the concentrations was beneficial for the anammox process to obtain resistance to different antibiotics with high concentrations. This study provides guidance for the stable operation of anammox-based biological treatment of antibiotics containing wastewater. [Display omitted] • Combined effects of two different antibiotics on anammox process were investigated. • Spiramycin and streptomycin at high concentrations inhibited anammox activity. • Correlations between dominant bacteria and key genes were evaluated. • The mechanism of multi-antibiotic resistance was illustrated based on results. [ABSTRACT FROM AUTHOR]