Competition among marine phytoplankton for different chelated iron species
Competition among marine phytoplankton for different chelated iron species
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DOI：
10.1038/23680
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发表时间：
1999-08-26
期刊：
影响因子：
64.8
通讯作者：
Luther, GW
中科院分区：
文献类型：
--
作者：
Hutchins, DA;Witter, AE;Luther, GW
溶解铁的有效性在控制海洋浮游植物生长方面起着关键作用(1，2)。溶解的铁绝大多数(类似于99%)与与铁(3-5)有很高亲和力的有机配体结合，但这种有机络合铁的来源、化学特性和生物有效性在很大程度上是未知的(6)。强络合铁的络合物释放到海水中可能是原核生物可诱导的铁吸收系统(铁载体络合物)(7-9)或通过浮游动物介导的细胞内物质的降解和释放(卟啉络合物)等过程造成的。在这里，我们使用培养的生物体和自然组合，比较了浮游植物对铁载体和卟啉络合物Fe-55的吸收。真核浮游植物有效地吸收与卟啉结合的铁，但这种铁源对原核浮游微藻(蓝藻)是相对不可用的，相反，与各种铁载体结合的铁对蓝藻比对真核生物更有效，这表明这两类浮游生物表现出根本不同的铁吸收策略。原核生物利用与内源铁载体(7-9)或外源铁载体(9)络合的铁，而真核生物可能依赖于铁还原酶系统(10，11)，该系统优先访问由四齿卟啉而不是六齿铁载体螯合的铁。因此，原核生物和真核生物之间对有机结合铁的竞争可能取决于可用铁络合物的化学性质，从而对低铁水域的生态位分离、浮游生物群落规模结构和碳输出产生影响。
Dissolved-iron availability plays a critical role in controlling phytoplankton growth in the oceans(1,2). The dissolved iron is overwhelmingly (similar to 99%) bound to organic ligands with a very high affinity for iron(3-5), but the origin, chemical identity and biological availability of this organically complexed Fe is largely unknown(6). The release into sea water of complexes that strongly chelate iron could result from the inducible iron-uptake systems of prokaryotes (siderophore complexes)(7-9) or by processes such as zooplankton-mediated degradation and release of intracellular material (porphyrin complexes). Here we compare the uptake of siderophore- and porphyrin-complexed Fe-55 by phytoplankton, using both cultured organisms and natural assemblages. Eukaryotic phytoplankton efficiently assimilate porphyrin-complexed iron, but this iron source is relatively unavailable to prokaryotic picoplankton (cyanobacteria), In contrast, iron bound to a variety of siderophores is relatively more available to cyanobacteria than to eukaryotes, suggesting that the two plankton groups exhibit fundamentally different iron-uptake strategies. Prokaryotes utilize iron complexed to either endogenous(7-9) or exogenous siderophores(9), whereas eukaryotes may rely on a ferrireductase system(10,11) that preferentially accesses iron chelated by tetradentate porphyrins, rather than by hexadentate siderophores. Competition between prokaryotes and eukaryotes for organically-bound iron may therefore depend on the chemical nature of available iron complexes, with consequences for ecological niche separation, plankton community size-structure and carbon export in low-iron waters.