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Abundant nitrite-oxidizing metalloenzymes in the mesopelagic zone of the tropical Pacific Ocean
Nature Geoscience ( IF 18.3 ) Pub Date : 2020-05-04 , DOI: 10.1038/s41561-020-0565-6
Mak A. Saito , Matthew R. McIlvin , Dawn M. Moran , Alyson E. Santoro , Chris L. Dupont , Patrick A. Rafter , Jaclyn K. Saunders , Drishti Kaul , Carl H. Lamborg , Marian Westley , Frederica Valois , John B. Waterbury

Numerous biogeochemical reactions occur within the oceans’ major oxygen minimum zones, but less attention has been paid to the open ocean extremities of these zones. Here we report measurements on oxygen minimum zone waters from the Eastern to the Central Tropical North Pacific, which we analysed using metaproteomic techniques to discern the microbial functions present and their influence on biogeochemical cycling. We found nitrite oxidoreductase—an iron-rich enzyme from Nitrospina bacteria—to be one of the most abundant microbial proteins present in the mesopelagic zone, with over 60 billion molecules per litre. Estimated reaction rates imply that this enzyme is undersaturated and that its high abundance provides a latent mesopelagic catalytic capacity to rapidly oxidize nitrite derived from episodic fluxes of degrading sinking organic matter. In addition, given the enzyme’s intensive iron demand, its high abundance represents a previously unrecognized microbial reservoir within suboxic mesopelagic zones. Nitrite oxidoreductase may also contribute to other reactions involving nitrogen and redox-sensitive metals. We suggest that the abundance and extent of nitrite oxidoreductase may increase with continued deoxygenation in the oceans, and result in increased mesopelagic demand for iron and other potential changes to marine biogeochemical cycles.



中文翻译:

热带太平洋近中生带中大量的亚硝酸盐氧化金属酶

在海洋的主要氧气最低限度区域内发生了许多生物地球化学反应,但对这些区域的开放海洋末端的关注较少。在这里,我们报告了从东部到中部热带北太平洋的最低氧带水域的测量值,我们使用元蛋白质组学技术对其进行了分析,以识别存在的微生物功能及其对生物地球化学循环的影响。我们发现亚硝酸盐氧化还原酶(一种来自亚硝基螺菌的富铁酶)细菌-是中生骨区中最丰富的微生物蛋白之一,每升分子超过600亿个分子。估计的反应速率表明该酶不饱和,并且其高丰度提供了潜在的中弹性催化能力,可以迅速氧化源自降解沉没有机物的情节性通量的亚硝酸盐。此外,考虑到该酶对铁的强烈需求,其高丰度代表了亚氧中膜弹性带区域内以前未被识别的微生物库。亚硝酸盐氧化还原酶也可能参与涉及氮和氧化还原敏感金属的其他反应。我们建议,随着海洋中持续脱氧,亚硝酸盐氧化还原酶的丰度和程度可能会增加,

更新日期:2020-05-04
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