Nitrate Storage and Dissimilatory Nitrate Reduction by Eukaryotic Microbes.
Nitrate Storage and Dissimilatory Nitrate Reduction by Eukaryotic Microbes.
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DOI：
10.3389/fmicb.2015.01492
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发表时间：
2015
影响因子：
5.2
通讯作者：
Stief P
中科院分区：
文献类型：
--
作者：
Kamp A;Høgslund S;Risgaard-Petersen N;Stief P
微生物氮循环是地球上最复杂和对环境最重要的元素循环之一，长期以来一直被认为完全由原核微生物介导。最近，人们发现某些真核微生物能够在细胞内储存硝酸盐，并在缺氧的情况下利用硝酸盐进行异化还原。这带来的范式转变在生态学上意义重大，因为所讨论的真核生物包括全球参与者，如硅藻、有孔虫和真菌。这篇综述文章提供了一个前所未有的概述硝酸盐储存和异化硝酸还原由不同的海洋真核生物置于生态生理背景下。在缺氧的栖息地中，细胞内硝酸盐储存对厌氧能量保存的优势得到了解释，并描述了这种代谢特性所带来的生活方式。首次编译了各种海洋沉积物的细胞内硝酸盐库存，表明细胞内硝酸盐池大大超过孔隙水硝酸盐池。在不同的海洋环境中，有孔虫对总沉积反硝化作用的相对贡献进行了估计，这表明真核生物在异化硝酸盐还原方面可能与原核生物相竞争。最后，本文概述了真核生物硝酸盐代谢的一些进化观点，并指出了未来研究中需要解决的开放性问题。
The microbial nitrogen cycle is one of the most complex and environmentally important element cycles on Earth and has long been thought to be mediated exclusively by prokaryotic microbes. Rather recently, it was discovered that certain eukaryotic microbes are able to store nitrate intracellularly and use it for dissimilatory nitrate reduction in the absence of oxygen. The paradigm shift that this entailed is ecologically significant because the eukaryotes in question comprise global players like diatoms, foraminifers, and fungi. This review article provides an unprecedented overview of nitrate storage and dissimilatory nitrate reduction by diverse marine eukaryotes placed into an eco-physiological context. The advantage of intracellular nitrate storage for anaerobic energy conservation in oxygen-depleted habitats is explained and the life style enabled by this metabolic trait is described. A first compilation of intracellular nitrate inventories in various marine sediments is presented, indicating that intracellular nitrate pools vastly exceed porewater nitrate pools. The relative contribution by foraminifers to total sedimentary denitrification is estimated for different marine settings, suggesting that eukaryotes may rival prokaryotes in terms of dissimilatory nitrate reduction. Finally, this review article sketches some evolutionary perspectives of eukaryotic nitrate metabolism and identifies open questions that need to be addressed in future investigations.