State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Siping Road, Shanghai 200092, P. R. China.
Advanced Water Management Centre (AWMC), The University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia.
Environ Sci Technol. 2020 Nov 17;54(22):14674-14685. doi: 10.1021/acs.est.0c02842. Epub 2020 Nov 4.
Understanding the recovery of anaerobic ammonium-oxidizing (anammox) bacteria after inhibition by dissolved oxygen (DO) is critical for the successful applications of anammox-based processes. Therefore, the effects of oxygen exposure (2 mg L DO for 90 min) and subsequent recovery treatments [N purging or nano zero-valent iron (nZVI) addition] on the activity and gene expression in a enrichment culture were examined. Combining the self-organizing map clustering and enrichment analysis, we proposed the oxidative stress response of anammox bacteria based on the existing concepts of oxidative stress in microbes: the DO exposure triggered a stringent response in , which downregulated the transcription levels of genes involved in the central metabolism and diverted energy to a flagellar assembly and metal transport modules; these changes possibly promoted survival during the inhibition of anammox activity. According to the cotranscription with central catabolism genes, putative reactive oxygen species (ROS) scavenger genes ( and ) were presumed to detoxify the anammox intermediates rather than ROS. In addition, both activity and mRNA profiles with appropriate amount of nZVI addition (5 and 25 mg L) were close to that of control, which proved the effectiveness of nZVI addition in anammox recovery. These results would be relevant to the physio-biochemistry development of anammox bacteria and further enhancement of nitrogen removal in wastewater treatment.
了解溶解氧（DO）抑制后厌氧氨氧化（anammox）细菌的恢复对于成功应用基于 anammox 的工艺至关重要。因此，考察了氧暴露（2 mg/L DO 持续 90 分钟）和随后的恢复处理[氮气吹扫或纳米零价铁（nZVI）添加]对富集培养物中活性和基因表达的影响。通过自组织映射聚类和富集分析相结合，我们根据微生物中现有的氧化应激概念提出了 anammox 细菌的氧化应激反应：DO 暴露触发了严格反应，下调了参与中心代谢的基因的转录水平，并将能量转移到鞭毛组装和金属转运模块；这些变化可能有助于在 anammox 活性抑制期间存活。根据与中心分解代谢基因的共转录，推测潜在的活性氧（ROS）清除剂基因（和）是为了清除 anammox 中间体而不是 ROS。此外，适量添加 nZVI（5 和 25 mg/L）时，活性和 mRNA 谱都接近对照，证明了 nZVI 添加在 anammox 恢复中的有效性。这些结果与 anammox 细菌的生理生化发展以及进一步增强废水处理中的氮去除有关。
