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The effects of Ni availability on H2 production and N2 fixation in a model unicellular diazotroph: The expression of hydrogenase and nitrogenase
Limnology and Oceanography ( IF 4.5 ) Pub Date : 2022-05-25 , DOI: 10.1002/lno.12151
Hsin-Ting Li, Sing-How Tuo, Mei-Chen Lu, Tung-Yuan Ho

We investigated the effects of Ni concentration on hydrogen (H2) net production and nitrogen (N2) fixation rates in a model unicellular diazotrophic cyanobacterium, Cyanothece. We quantified NiFe uptake hydrogenase of the diazotroph to examine how Ni deficiency affects the expression of hydrogenase and nitrogenase and N2 fixation rates. We found that Ni availability controls its H2 net production and the expression of HupL, the major subunit of the uptake hydrogenase. Low Ni availability induced low HupL expression levels while yielding high H2 net production, and vice versa. We also identified the threshold range of Ni concentrations that may differentiate low and high H2 net production patterns in the diazotroph. However, the substantial variations in Ni availability and H2 net production did not affect nitrogenase expression and N2 fixation rates in Cyanothece. From two independent studies in the Atlantic tropical and subtropical oceans, we found that dissolved Ni concentrations and H2 oversaturation percentage exhibited a statistically significant negative correlation, which is consistent with the findings of this culture study. Overall, these results indicate that Ni availability may affect H2 net production and concentrations in the euphotic zone of the oceanic regions. H2 concentrations may be used as a promising proxy to reflect N2 fixation activities in tropical and subtropical oceans only under Ni-deficient conditions.

中文翻译:

Ni可用性对模型单细胞固氮菌中H2产生和N2固定的影响:氢化酶和固氮酶的表达

我们研究了 Ni 浓度对模型单细胞固氮蓝藻Cyanothece中氢 (H 2 ) 净产量和氮 (N 2 ) 固定率的影响。我们量化了固氮菌的 NiFe 摄取氢化酶,以检查 Ni 缺乏如何影响氢化酶和固氮酶的表达以及 N 2固定率。我们发现 Ni 可用性控制其 H 2净产量和 HupL 的表达,HupL 是摄取氢化酶的主要亚基。低镍可用性导致低 HupL 表达水平,同时产生高 H 2净产量,反之亦然。我们还确定了可以区分低 H 和高 H 的 Ni 浓度的阈值范围2固氮菌的净生产模式。然而,Ni 利用率和 H 2净产量的显着变化并不影响Cyanothece中固氮酶的表达和 N 2固定率。从大西洋热带和亚热带海洋的两项独立研究中,我们发现溶解的 Ni 浓度和 H 2过饱和百分比呈现出统计学上显着的负相关,这与本培养研究的结果一致。总体而言,这些结果表明,Ni 可用性可能会影响海洋区域透光区的 H 2净产量和浓度。H 2浓度可用作仅在缺镍条件下反映热带和亚热带海洋中N 2固定活动的有希望的代理。
更新日期:2022-05-25
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