Abundant nitrite-oxidizing metalloenzymes in the mesopelagic zone of the tropical Pacific Ocean
Abundant nitrite-oxidizing metalloenzymes in the mesopelagic zone of the tropical Pacific Ocean
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DOI：
10.1038/s41561-020-0565-6
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发表时间：
2020-05
影响因子：
18.3
通讯作者：
M. Saito;M. McIlvin;D. Moran;A. Santoro;C. Dupont;P. Rafter;Jaclyn K. Saunders;D. Kaul;C. Lamborg;Marian B. Westley;F. Valois;J. Waterbury
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作者：
M. Saito;M. McIlvin;D. Moran;A. Santoro;C. Dupont;P. Rafter;Jaclyn K. Saunders;D. Kaul;C. Lamborg;Marian B. Westley;F. Valois;J. Waterbury
许多生物地球化学反应发生在海洋的主要氧气最低区域内，但对这些区域的公海末端的关注较少。在这里，我们报告了从热带北太平洋东部到中部氧气最低区水域的测量结果，我们使用宏蛋白质组学技术进行分析，以辨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（一种来自硝化脊柱细菌的富含铁的酶）是中层区域中最丰富的微生物蛋白质之一，每升含有超过 600 亿个分子。估计的反应速率意味着这种酶是不饱和的，并且其高丰度提供了潜在的中层催化能力，可以快速氧化源自降解下沉有机物的间歇通量的亚硝酸盐。此外，考虑到这种酶对铁的强烈需求，其高丰度代表了低氧中层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有助于涉及氮和氧化还原敏感金属的其他反应。我们认为，随着海洋中持续脱氧，亚硝酸盐氧化还原酶的丰度和范围可能会增加，并导致中层对铁的需求增加以及海洋生物地球化学循环的其他潜在变化。
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 fromNitrospinabacteria—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.