Processes regulating cellular metal accumulation and physiological effects: Phytoplankton as model systems
Processes regulating cellular metal accumulation and physiological effects: Phytoplankton as model systems
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DOI：
10.1016/s0048-9697(98)00226-5
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发表时间：
1998-08-28
影响因子：
9.8
通讯作者：
Huntsman, SA
中科院分区：
文献类型：
--
作者：
Sunda, WG;Huntsman, SA
微量金属存在多种氧化还原态和配位态，这对其地球化学行为和生物有效性有显著影响。大多数以金属阳离子的形式存在于天然水中，与无机和有机配体有不同程度的络合。金属离子通常通过细胞膜运输蛋白进入细胞，这些蛋白被设计用于获取营养金属（Mg, Fe, Mn, Zn, Co, Cu, Mo）。有机配体与这些运输蛋白竞争结合金属离子，因此，有机络合大大降低了金属的摄取速率。通常，螯合金属不能直接用于细胞摄取，金属的摄取由自由水合离子的浓度或动力学上不稳定的无机物质的浓度控制。然而，运输蛋白的配位位点并不完全针对预期的营养金属，因此会与非营养或有毒金属结合并运输。对膜运输位点和细胞内代谢结合位点的竞争可以极大地影响营养和有毒金属的吸收，并由此对生长速度产生影响。这种生长速率效应对细胞内的金属浓度提供反馈，因为细胞内积累的金属量代表了金属吸收率与细胞生长速率（有效生物稀释率）之间的平衡。浮游植物为研究调节细胞金属积累及其生理效应的过程和相关的化学和生物因素提供了有用的模型系统。(C) 1998 Elsevier Science B.V.版权所有
Trace metals exist in a variety of redox states and coordination species which markedly influences their geochemical behavior and biological availability. Most exist in natural waters as metal cations that are complexed to varying degrees by inorganic and organic ligands. Metal ions are generally taken up into cells by membrane transport proteins designed for acquisition of nutrient metals (Mg, Fe, Mn, Zn, Co, Cu, Mo). Organic ligands compete with these transport proteins for binding metal ions, and consequently, organic complexation substantially decreases metal uptake rates. Typically, the chelated metal is not directly available for cellular uptake, and metal uptake is controlled by either the concentration of free aquo ions or that of kinetically labile inorganic species. The coordination sites of transport proteins, however, are not entirely specific for intended nutrient metals, and consequently will bind with and transport non-nutritive or toxic metals. Competition for membrane transport sites and for intracellular metabolic binding sites can substantially influence the uptake of both nutrient and toxic metals and resultant effects on growth rate. Such growth rate effects provide feedback on cellular metal concentrations since the amount of metal accumulated within cells represents a balance between the rate of metal uptake and the cellular growth rate, the effective biodilution rate. Phytoplankton have provided useful model systems for investigating the processes and associated chemical and biological factors regulating cellular metal accumulation and resultant physiological effects. (C) 1998 Elsevier Science B.V. All rights reserved.