从典型硝化细菌到全程氨氧化微生物：发现及研究进展

生物硝化过程在全球氮循环中起关键性作用,被认为由氨氮氧化成亚硝酸盐和亚硝酸盐氧化成硝酸盐两个步骤组成,分别由氨氧化微生物(Ammonia oxidizing microorganisms,AOM)和硝化细菌(Nitrite oxidizing bacteria,NOB)催化完成。AOM包括氨氧化细菌(Ammonia oxidizing bacteria,AOB)和氨氧化古菌(Ammonia oxidizing archaea,AOA),AOB与AOA分布广泛,两者的相对丰度和氨氮浓度密切相关。2015年底,3个硝化螺菌属(Nitrospira)谱系Ⅱ的NOB被证实含有AOM的特征功能酶,包括氨单加氧酶(AMO)和羟胺脱氢酶(HAO),并证明NOB同时具有氨氧化和亚硝酸盐氧化的能力,命名为全程氨氧化微生物(Complete ammonia oxidizer,Comammox)。根据AMO的α亚基基因amoA的相似性将Comammox分为两大分支clade A和clade B。它们广泛分布于自然环境和人工系统,包括土壤(稻田、森林)、淡水(湿地、河流、湖泊沉积物、蓄水层)、污水处理厂和自来水厂等。本文综述了Comammox的发现及其最新的研究进展,并展望了Comammox作为氮循环关键功能菌群的研究方向和应用前景。

From canonical nitrite oxidizing bacteria to complete ammonia oxidizer: discovery and advances

Biological nitrification plays a key role in the global nitrogen cycle, which is considered to consist of two serial steps of ammonia oxidation to nitrite biocatalyzed by ammonia oxidizing microorganisms (AOM) and nitrite to nitrate biocatalyzed by nitrite oxidizing bacteria (NOB). AOM include ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA), which are widely spread with relative abundances closely related to the concentration of ammonia. In 2015, three bacteria belonging to Nitrospira lineage II with NOB-specific functional genes were identified to carry AOM-specific functional enzymes including ammonia monooxygenase (AMO) and hydroxylamine oxidoreductase (HAO), and proved their capacity to completely oxidize ammonia to nitrate. They have been named complete ammonia oxidizer (Comammox). Comammox could be subdivided into two branches of clade A and clade B based on the sequence discrepancy of ammonia monooxygenase subunit alpha (amoA), which have been widely found in natural and engineered environments such as soil (paddy soil, forest), fresh water (wetland, river, lake sediments, aquifers), wastewater and drinking water treatment plants. This paper introduces the discovery and distribution of Comammox, focuses on reviewing the research development on Comammox and prospects its research and application as a significant functional group of nitrogen cycle.