Photosynthesis and calcification by Emiliania huxleyi (Prymnesiophyceae) as a function of inorganic carbon species
Photosynthesis and calcification by Emiliania huxleyi (Prymnesiophyceae) as a function of inorganic carbon species
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DOI：
10.1046/j.1529-8817.1999.3550949.x
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发表时间：
1999-10-01
影响因子：
2.9
通讯作者：
Veldhuis, MJW
中科院分区：
文献类型：
--
作者：
Buitenhuis, ET;de Baar, HJW;Veldhuis, MJW
为了测试海洋单细胞藻草草和莫勒对无机碳限制的可能性，测定了不同化学形态的无机碳对海洋单细胞藻类的碳摄取。由于这些不同的物种在任何改变物种形成的实验中都是相互依赖和相互变化的，因此进行了一系列实验，以产生用于光合作用和钙化的多维碳吸收方案。这一方案表明，用于光合作用的二氧化碳来自两个来源。海水中的二氧化碳支持适度的光合作用。HCO3-是光合作用的主要底物，胞内产生CO2(HCO3-+H+-->；CO2+H2O-->；CH2O+O-2)。HCO3-的这种使用是可能的，因为同时使用第二个HCO3-进行钙化，该第二个HCO3-提供所需的质子(HCO3-+Ca2+-->；CaCO3+H+)。HCO3-是钙化的唯一底物。通过对用于光合作用的两种CO_2来源的区分，表明湖北龙须草对外部CO_2的K-1/2仅为1.9+/-0.5亩M(V-max为2.4+/-0.1pmol.cell(-1)·d(-1))。因此，在与大气平衡的海水中([CO2]=14亩M，[HCO3-]=1920亩M，FCO(2)=360亩大气压，pH=8，T=15℃)，光合作用90%被外部CO2饱和。在相同条件下，CO2供应的钙化途径(从2.1 pmol.cell(-1)·d(-1))使光合作用速率加倍。然而，光合作用并不是完全饱和的，因为钙化作用的HCO3-的K-1/2为3256+/-1402亩M，V-max为6.4+/-1.8 pmol.cell(-1)·d(-1)。钙化过程中产生的H+的使用效率为0.97+/-0.08，得出的结论是它是在细胞内使用的。可以预期的最大效率为0.88，因为NO3-吸收会为细胞产生一个H+汇(OH-源)。湖北龙须草的成功可能与钙化过程中H+的产生和光合作用中CO2固定之间的有效耦合有关。
To test the possibility of inorganic carbon limitation of the marine unicellular alga Emiliania huxleyi (Lohmann) Hay and Mohler, its carbon acquisition was measured as a function of the different chemical species of inorganic carbon present in the medium. Because these different species are interdependent and covary in any experiment in which the speciation is changed, a set of experiments was performed to produce a multidimensional carbon uptake scheme for photosynthesis and calcification. This scheme shows that CO2 that is used for photosynthesis comes from two sources. The CO2 in seawater supports a modest rate of photosynthesis. The HCO3- is the major substrate for photosynthesis by intracellular production of CO2 (HCO3- + H+ --> CO2 + H2O --> CH2O + O-2). This use of HCO3- is possible because of the simultaneous calcification using a second HCO3-, which provides the required proton (HCO3- + Ca2+ --> CaCO3 + H+). The HCO3- is the only substrate for calcification. By distinguishing the two sources of CO2 used in photosynthesis, it was shown that E. huxleyi has a K-1/2 for external CO2 of "only" 1.9 +/- 0.5 mu M (and a V-max of 2.4 +/- 0.1 pmol.cell(-1).d(-1)). Thus, in seawater that is in equilibrium with the atmosphere ([CO2] = 14 mu M, [HCO3-] = 1920 mu M, at fCO(2) = 360 mu atm, pH = 8, T = 15 degrees C), photosynthesis is 90% saturated with external CO2. Under the same conditions, the rate of photosynthesis is doubled by the calcification route of CO2 supply (from 2.1 to 4.5 pmol.cell(-1).d(-1)). However, photosynthesis is not fully saturated, as calcification has a K-1/2 for HCO3- of 3256 +/- 1402 mu M and a V-max of 6.4 +/- 1.8 pmol.cell(-1).d(-1). The H+ that is produced during calcification is used with an efficiency of 0.97 +/- 0.08, leading to the conclusion that it is used intracellularly. A maximum efficiency of 0.88 can be expected, as NO3- uptake generates a H+ sink (OH- source) for the cell. The success of E. huxleyi as a coccolithophorid may be related to the efficient coupling between H+ generation in calcification and CO2 fixation in photosynthesis.