Nitrogen isotope effects induced by anammox bacteria
Nitrogen isotope effects induced by anammox bacteria
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DOI：
10.1073/pnas.1310488110
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发表时间：
2013-11-19
影响因子：
11.1
通讯作者：
Kuypers, Marcel M. M.
中科院分区：
文献类型：
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作者：
Brunner, Benjamin;Contreras, Sergio;Kuypers, Marcel M. M.
氮 (N) 同位素比 (N-15/N-14) 为现代海洋的氮库存提供了综合约束。厌氧氨氧化（anammox）将铵和亚硝酸盐转化为氮气（N-2）和硝酸盐，是海洋生态系统中重要的固定氮汇。我们在分批培养实验中研究了迄今为止未知的厌氧氨氧化氮同位素效应。厌氧氨氧化优先从铵池中去除 N-14，同位素效应为 +23.5% 至 +29.1%，具体取决于控制可逆性的因素。亚硝酸盐转化为 N-2 和硝酸盐期间的 N 同位素效应是 (i) 与亚硝酸盐氧化为硝酸盐 (-31.1 +/- 3.9%) 相关的逆动力学 N 同位素分馏，(ii) 亚硝酸盐还原为 N-2 (+16.0 +/- 4.5%) 期间的正常动力学 N 同位素分馏，以及 (iii) 硝酸盐和亚硝酸盐之间的平衡 N 同位素效应(-60.5 +/- 1.0%)，当厌氧氨氧化暴露于环境压力时诱导，导致氮同位素交换效应对动态氮同位素分馏的叠加。我们的研究结果表明，厌氧氨氧化可能是造成海洋含氧最低区硝酸盐和亚硝酸盐之间未解决的大氮同位素偏移的原因。无论硝酸盐和亚硝酸盐之间的 N 同位素交换程度如何，从亚硝酸盐和硝酸盐 (NOx) 合并池中去除的 N 相对于 NOx 而言在 N-15 中是贫乏的。厌氧氨氧化的净氮同位素效应叠加在低氧水域中同时发生的硝酸盐还原成亚硝酸盐的氮同位素分馏上，可能增强氧最低区氮损失的总体氮同位素效应。
Nitrogen (N) isotope ratios (N-15/N-14) provide integrative constraints on the N inventory of the modern ocean. Anaerobic ammonium oxidation (anammox), which converts ammonium and nitrite to dinitrogen gas (N-2) and nitrate, is an important fixed N sink in marine ecosystems. We studied the so far unknown N isotope effects of anammox in batch culture experiments. Anammox preferentially removes N-14 from the ammonium pool with an isotope effect of +23.5% to +29.1%, depending on factors controlling reversibility. The N isotope effects during the conversion of nitrite to N-2 and nitrate are (i) inverse kinetic N isotope fractionation associated with the oxidation of nitrite to nitrate (-31.1 +/- 3.9%), (ii) normal kinetic N isotope fractionation during the reduction of nitrite to N-2 (+16.0 +/- 4.5%), and (iii) an equilibrium N isotope effect between nitrate and nitrite (-60.5 +/- 1.0%), induced when anammox is exposed to environmental stress, leading to the superposition of N isotope exchange effects upon kinetic N isotope fractionation. Our findings indicate that anammox may be responsible for the unresolved large N isotope offsets between nitrate and nitrite in oceanic oxygen minimum zones. Irrespective of the extent of N isotope exchange between nitrate and nitrite, N removed from the combined nitrite and nitrate (NOx) pool is depleted in N-15 relative to NOx. This net N isotope effect by anammox is superimposed on the N isotope fractionation by the co-occurring reduction of nitrate to nitrite in suboxic waters, possibly enhancing the overall N isotope effect for N loss from oxygen minimum zones.