Nickel limitation and zinc toxicity in a urea-grown diatom
Nickel limitation and zinc toxicity in a urea-grown diatom
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DOI：
10.4319/lo.2008.53.6.2462
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发表时间：
2008-11-01
影响因子：
4.5
通讯作者：
Morel, Francois M. M.
中科院分区：
文献类型：
--
作者：
Egleston, Eric S.;Morel, Francois M. M.
当以尿素为氮源生长时，硅藻必须积累镍（Ni），镍是水解尿素的尿素酶中的辅因子。鉴于Ni（2+）离子与吸收配体的反应速率缓慢，在低环境浓度下吸收Ni特别具有挑战性。正如预期的那样，模式硅藻海链藻和海链藻的培养物在非常低的镍浓度下变得受限，当生长在尿素上而不是硝酸盐或铵作为氮源时。在高镍浓度下，尿素培养的T. weissflocculus表现出类似的积累各种其他金属硝酸盐生长的文化和相同的敏感性，锌和铜（Zn和Cu）的浓度。但在低Ni浓度下，T.在尿素上生长的Weissflorescence细胞积累过量的Zn，并表现出对Zn毒性的极端敏感性。看来，锌积累在低镍浓度下生长的细胞通过摄取通过上调的镍运输系统。由此产生的敏感性的镍有限的细胞锌（或其他金属，可以采取通过镍运输系统）可能会限制使用尿素作为氮的来源，在海洋中的一些浮游植物物种。
When growing on urea as a nitrogen source, diatoms must accumulate nickel (Ni), a cofactor in the urease enzyme, which hydrolyzes urea. The uptake of Ni at low ambient concentrations is particularly challenging in view of the slow rate of reaction of the Ni(2+) ion with uptake ligands. As expected, cultures of the model diatoms Thalassiosira weissflogii and Thalassiosira pseudonana become limited at very low Ni concentrations when growing on urea but not on nitrate or ammonium as a nitrogen source. At high Ni concentrations, urea-grown cultures of T. weissflogii exhibit similar accumulation of various other metals to nitrate-grown cultures and the same sensitivity to zinc and copper (Zn and Cu) concentrations. But at low Ni concentrations, T. weissflogii cells growing on urea accumulate excess Zn and exhibit extreme sensitivity to Zn toxicity. It appears that Zn accumulates in cells growing at low Ni concentrations by uptake through the up-regulated Ni transport system. The resulting sensitivity of Ni-limited cells to Zn (or to other metals that may be taken up via the Ni transport system) may limit the use of urea as a source of nitrogen in the oceans by some phytoplankton species.