Combined effects of temperature and iron on the growth and physiology of the marine diatom, Phaeodactylum tricornutum (Bacillariophyceae)
Combined effects of temperature and iron on the growth and physiology of the marine diatom, Phaeodactylum tricornutum (Bacillariophyceae)
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DOI：
10.1046/j.1529-8817.2000.99042.x
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发表时间：
2000-12-01
影响因子：
2.9
通讯作者：
Maita, Y
中科院分区：
文献类型：
--
作者：
Kudo, I;Miyamoto, M;Maita, Y
三角褐指藻（硅藻纲）在5 - 30 ℃的温度范围内，在充满铁和胁迫的条件下维持指数生长，在20 ℃观察到最大生长速率（CR（最适温度），在最适温度以下，CR下降温度逐渐降低;然而，当温度升高到最适温度以上时，生长速率急剧下降，在20 ℃时，Fe胁迫细胞的生长速率是Fe充足细胞的生长速率的一半，而在较低温度下，这种差异变得更大，代谢活动的变化除了最适温度外，还表现出与生长速率温度变化相似的模式，每个细胞的硝酸还原酶活性（NRA）和呼吸电子传递系统活性（ETS）在15至20摄氏度之间最大，而对于Fe-充满的细胞，细胞特异性光合速率（P-细胞）在20摄氏度最大，这些代谢活动受到铁缺乏的影响，这与这些活动应该具有铁依赖性的理论预测一致，但是，铁缺乏对所研究的四种代谢活动的影响程度是不同的：NRA > P-cell > ETS = GR，在相同温度下，铁胁迫细胞的NRA仅为铁胁迫细胞的10%，这些结果表明，细胞将有不同的铁需求的每一个代谢途径或铁供应的优先权，每一个代谢反应是有关的铁营养。与此相反，从最适温度开始降低温度的影响顺序为ETS > P-cell > NRA > GR。对于NRA，所观察到的温度依赖性不能用酶反应速率本身的温度依赖性来解释，酶反应速率几乎随温度而恒定，这表明酶的产生是温度依赖性的。这是首次报道铁和温度对三种重要代谢活性的联合影响（NRA，P-细胞和ETS），并确定哪些活动受铁缺乏的影响最大，细胞组成也受到铁缺乏的影响，显示在Fe-应激的细胞中较低的Chia含量。当温度从20 ° C降低到10 ° C时，在充满Fe的条件下，每细胞体积的Chi a降低了30%，但是从充满Fe的条件到受Fe胁迫的条件下，chi a降低了50%，
Phaedactylum tricornutum Bohlin (Bacillariophyceae) was maintained in exponential growth under Fe-replete and stressed conditions over a range of temperatures from 5 to 30 degrees C, The maximum growth rate (CR) was observed at 20 degrees C (optimal temperature) for Fe-replete and stressed cells, There was a gradual decrease in the CR decreasing temperatures below the optimum temperature; however, the growth rate dropped sharply as temperature increased above the optimum temperature, Fe-stressed cells grew at half the growth rate of Fe-replete cells at 20 degrees C, whereas this difference became larger at lower temperatures, The change in metabolic activities showed a similar pattern to the change in growth rate temperature aside from their optimum temperature, Nitrate reductase activity (NRA) and respiratory electron transport system activity (ETS) per cell were maximal between 15 and 20 degrees C, whereas cellspecific photosynthetic rate (P-cell) was maximal at 20 degrees C for Fe-replete cells, These metabolic activities were influenced by Fe deficiency, which is consistent with the theoretical prediction that these activities should have an Fe dependency, The degree of influence of Fe deficiency, however, was different for the four metabolic activities studied: NRA > P-cell > ETS = GR, NRA in Fe-stressed cells was only 10% of that in Fe-replete cells at the same temperature, These results suggest that cells would have different Fe requirements for each metabolic pathway or that the priority of Fe supply to each metabolic reaction is related to Fe nutrition. Tn contrast, the order of influence of decreasing the temperature from the optimum temperature was ETS > P-cell > NRA > GR, For NRA, the observed temperature dependency could not be accounted for by the temperature dependency of the enzyme reaction rate itself that was almost constant with temperature, suggesting that production of the enzyme would be temperature dependent, For ETS, both the enzyme reactivity and the amount of enzyme accounted for the dependency, This is the first report to demonstrate the combined effects of Fe and temperature on three important metabolic activities (NRA, P-cell, and ETS) and to determine which activity is affected the most by a shortage of Fe, Cellular composition was also influenced by Fe deficiency, showing lower chi a content in the Fe-stressed cells. Chi a per cell volume decreased by 30% as temperature decreased from 20 to 10 degrees C under Fe-replete conditions, but chi a decreased by 50% from Fe-replete to Fe-stressed conditions,