Anaerobic ammonium oxidation (anammox) is a relatively new pathway within the N cycle discovered in the late 1990s. This eminent discovery not only modified the classical theory of biological metabolism and matter cycling, but also profoundly influenced our understanding of the energy sources for life. A new member of chemolithoautotrophic microorganisms capable of carbon fixation was found in the vast deep dark ocean. If the discovery of the chemosynthetic ecosystems in the deep-sea hydrothermal vent environments once challenged the old dogma “all living things depend on the sun for growth,” the discovery of anammox bacteria that are widespread in anoxic environments fortifies the victory over this dogma. Anammox bacteria catalyze the oxidization of NH4+ by using NO2- as the terminal electron acceptor to produce N2. Similar to the denitrifying microorganisms, anammox bacteria play a biogeochemical role of inorganic N removal from the environment. However, unlike heterotrophic denitrifying bacteria, anammox bacteria are chemolithoautotrophs that can generate transmembrane proton motive force, synthesize ATP molecules and further carry out CO2 fixation through metabolic energy harvested from the anammox process. Although anammox bacteria and the subsequently found ammonia-oxidizing archaea (AOA), another very important group of N cycling microorganisms are both chemolithoautotrophs, AOA use ammonia rather than ammonium as the electron donor and O2 as the terminal electron acceptor in their energy metabolism. Therefore, the ecological process of AOA mainly takes place in oxic seawater and sediments, while anammox bacteria are widely distributed in anoxic water and sediments, and even in some typical extreme marine environments such as the deep-sea hydrothermal vents and methane seeps. Studies have shown that the anammox process may be responsible for 30%–70% N2 production in the ocean. In environmental engineering related to nitrogenous wastewater treatment, anammox provides a new technology with low energy consumption, low cost, and high efficiency that can achieve energy saving and emission reduction. However, the discovery of anammox bacteria is actually a hard-won achievement. Early in the 1960s, the possibility of the anammox biogeochemical process was predicted to exist according to some marine geochemical data. Then in the 1970s, the existence of anammox bacteria was further predicted via chemical reaction thermodynamic calculations. However, these microorganisms were not found in subsequent decades. What hindered the discovery of anammox bacteria, an important N cycling microbial group widespread in hypoxic and anoxic environments? What are the factors that finally led to their discovery? What are the inspirations that the analyses of these questions can bring to scientific research? This review article will analyze and elucidate the above questions by presenting the fundamental physiological and ecological characteristics of the marine anammox bacteria and the principles of scientific research.

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厌氧菌细菌科学发现的启示：科学原理如何指导发现和发展的经典例子

厌氧铵氧化（厌氧氨）是1990年代后期发现的N循环中一个相对较新的途径。这一重大发现不仅改变了生物代谢和物质循环的经典理论，而且深刻地影响了我们对生命能量来源的理解。在广阔的深海中发现了一种能够固碳的化石自养微生物的新成员。如果在深海热液喷口环境中发现化学合成生态系统曾经挑战过旧的教条“所有生物都依靠阳光来生长”，那么在缺氧环境中广泛分布的厌氧细菌的发现就证明了对这一教条的胜利。厌氧氨氧化细菌通过使用NO2-作为末端电子受体来产生N2，从而催化NH4 +的氧化。与反硝化微生物相似，厌氧氨氧化细菌在从环境中去除无机氮方面起着生物地球化学的作用。然而，与异养反硝化细菌不同，厌氧氨氧化细菌是化学自噬菌，可以产生跨膜质子原动力，合成ATP分子，并通过从厌氧氨氧化过程中收集的代谢能进一步固定CO2。尽管厌氧细菌和随后发现的氨氧化古细菌（AOA），另一组非常重要的N循环微生物都是化学自养菌，AOA在能量代谢中使用氨而不是铵作为电子供体，并使用O2作为末端电子受体。因此，AOA的生态过程主要发生在含氧海水和沉积物中，而厌氧细菌则广泛分布在缺氧的水和沉积物中，甚至在一些典型的极端海洋环境中，例如深海热液喷口和甲烷渗漏。研究表明，厌氧氨氧化过程可能导致海洋中30％–70％的N2产生。在与含氮废水处理相关的环境工程中，厌氧氨氧化技术提供了一种低能耗，低成本和高效率的新技术，可以实现节能减排。然而，厌氧氨氧化细菌的发现实际上是来之不易的成就。根据一些海洋地球化学数据，预计在1960年代初期存在厌氧氨氧化生物地球化学过程的可能性。然后在1970年代，通过化学反应热力学计算进一步预测了厌氧细菌的存在。但是，在随后的几十年中没有发现这些微生物。是什么阻碍了厌氧菌的发现，厌氧菌是在缺氧和缺氧环境中广泛分布的重要的N循环微生物群？最终导致他们发现的因素是什么？这些问题的分析可以给科学研究带来什么启示？本文将通过介绍海洋厌氧氨氧化细菌的基本生理学和生态学特征以及科学研究原理，来分析和阐明上述问题。在缺氧和缺氧环境中分布的重要的N循环微生物群吗？最终导致他们发现的因素是什么？这些问题的分析可以给科学研究带来什么启示？本文将通过介绍海洋厌氧氨氧化细菌的基本生理学和生态学特征以及科学研究原理，来分析和阐明上述问题。在缺氧和缺氧环境中分布的重要的N循环微生物群吗？最终导致他们发现的因素是什么？这些问题的分析可以给科学研究带来什么启示？本文将通过介绍海洋厌氧氨氧化细菌的基本生理学和生态学特征以及科学研究原理，来分析和阐明上述问题。