In the past 20 years, there has been a major stride in understanding the core mechanism of anaerobic ammonium-oxidizing (anammox) bacteria, but there are still several discussion points on their survival strategies. Here, we discovered a new genus of anammox bacteria in a full-scale wastewater-treating biofilm system, tentatively named “Candidatus Loosdrechtia aerotolerans”. Next to genes of all core anammox metabolisms, it encoded and transcribed genes involved in the dissimilatory nitrate reduction to ammonium (DNRA), which coupled to oxidation of small organic acids, could be used to replenish ammonium and sustain their metabolism. Surprisingly, it uniquely harbored a new ferredoxin-dependent nitrate reductase, which has not yet been found in any other anammox genome and might confer a selective advantage to it in nitrate assimilation. Similar to many other microorganisms, superoxide dismutase and catalase related to oxidative stress resistance were encoded and transcribed by “Ca. Loosdrechtia aerotolerans”. Interestingly, bilirubin oxidase (BOD), likely involved in oxygen resistance of anammox bacteria under fluctuating oxygen concentrations, was identified in “Ca. Loosdrechtia aerotolerans” and four Ca. Brocadia genomes, and its activity was demonstrated using purified heterologously expressed proteins. A following survey of oxygen-active proteins in anammox bacteria revealed the presence of other previously undetected oxygen defense systems. The novel cbb3-type cytochrome c oxidase and bifunctional catalase-peroxidase may confer a selective advantage to Ca. Kuenenia and Ca. Scalindua that face frequent changes in oxygen concentrations. The discovery of this new genus significantly broadens our understanding of the ecophysiology of anammox bacteria. Furthermore, the diverse oxygen tolerance strategies employed by distinct anammox bacteria advance our understanding of their niche adaptability and provide valuable insight for the operation of anammox-based wastewater treatment systems.

在过去的 20 年里，对厌氧氨氧化 (anammox) 细菌的核心机制的理解有了重大进展，但关于它们的生存策略仍有几个讨论点。在这里，我们在全规模废水处理生物膜系统中发现了一种新的厌氧氨氧化菌属，暂定名为“ Candidatus ”Loosdrechtia aerotolerans”。除了所有核心厌氧氨氧化代谢的基因外，它还编码和转录参与硝酸盐异化还原为铵 (DNRA) 的基因，该过程与小有机酸的氧化相结合，可用于补充铵并维持其代谢。令人惊讶的是，它独特地含有一种新的铁氧还蛋白依赖性硝酸盐还原酶，该酶尚未在任何其他厌氧氨氧化基因组中发现，并且可能赋予它在硝酸盐同化中的选择性优势。与许多其他微生物类似，与抗氧化应激相关的超氧化物歧化酶和过氧化氢酶由“ Ca. Loosdrechtia aerotolerans”。有趣的是，在“ Ca. Loosdrechtia aerotolerans”和四个Ca。Brocadia 基因组及其活性使用纯化的异源表达蛋白进行了证明。随后对厌氧氨氧化细菌中氧活性蛋白的调查揭示了其他以前未检测到的氧气防御系统的存在。新型cbb3型细胞色素 c 氧化酶和双功能过氧化氢酶-过氧化物酶可能赋予Ca选择性优势。Kuenenia 和Ca. 面临氧气浓度频繁变化的 Scalindua。这一新属的发现显着拓宽了我们对厌氧氨氧化细菌生态生理学的理解。此外，不同厌氧氨氧化细菌采用的多种耐氧策略促进了我们对其生态位适应性的理解，并为基于厌氧氨氧化的废水处理系统的运行提供了宝贵的见解。