​Science：既耗氧又能产氧的古菌

Oxygen and nitrogen production by an ammonia-oxidizing archaeon

作者：Beate Kraft, Nico Jehmlich, Morten Larsen, Laura A. Bristow, Martin Könneke, Bo Thamdrup, Donald E. Canfield

Science：2022/01/07

Ammonia-oxidizing archaea (AOA) are one of the most abundant groups of microbes in the world’s oceans and are key players in the nitrogen cycle. Their energy metabolism—the oxidation of ammonia to nitrite—requires oxygen. Nevertheless, AOA are abundant in environments where oxygen is undetectable. By carrying out incubations for which oxygen concentrations were resolved to the nanomolar range, we show that after oxygen depletion, Nitrosopumilus maritimus produces dinitrogen and oxygen, which is used for ammonia oxidation. The pathway is not completely resolved but likely has nitric oxide and nitrous oxide as key intermediates. N. maritimus joins a handful of organisms known to produce oxygen in the dark. On the basis of this ability, we reevaluate the role of N. maritimus in oxygen-depleted marine environments.

氨氧化古菌（Ammonia-oxidizing archaea）是海洋中最丰富的一个微生物群，能促进海洋的氮循环。它们主要通过将氨氧化为亚硝酸盐来获得能量，这个过程需要氧气。然而，此前的研究发现，很多氨氧化古菌能生活在缺氧的环境中，其具体的生存方式尚不清楚。在一项发表于《科学》的新研究中，科学家研究了一种氨氧化古菌Nitrosopumilus maritimus，揭示了它能在缺氧环境中生存的原因。

他们发现，在缺氧、黑暗的环境中，这种古菌物能产生氮气和氧气（够细菌自身使用），并将氧气用于氧化氨为自身供能。目前，他们还不完全确定这条反应途径，但认为NO和N2O或是其中的中间产物。研究人员认为，Nitrosopumilus maritimus能将氧气与气态氮的生产结合起来，通过这种方式，它们能去除海洋中的生物有效氮，促进氮循环。