Stolte Willem, Kraay Gijsbert W, Noordeloos Anna A M, Riegman Roel
Department of Biological Oceanography, Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, The Netherlands.
J Phycol. 2000 Jun;36(3):529-539. doi: 10.1046/j.1529-8817.2000.99158.x.
Genetic variation of pigment composition was studied in 16 different strains of Emiliania huxleyi (Lohm.) Hay et Mohler in batch culture. Distinct strain-dependent differences were found in the ratios of fucoxanthin, 19'-hexanoyloxyfucoxanthin, and 19'-butanoyloxyfucoxanthin, hampering the use of these individual pigments as a taxonomic marker at the species level. The molar ratio of total carotenoids to chl a, however, was constant for all strains tested. In addition, the pigment composition of one axenic strain (L) of E. huxleyi at different growth rates in light-, nitrate-, and phosphate-limited continuous cultures was analyzed quantitatively. The pigments fucoxanthin and 19'-hexanoyloxyfucoxanthin correlated closely under all conditions. From steady-state rate calculations, it is hypothesized that 19'-hexanoyloxyfucoxanthin is synthesized from fucoxanthin, with light as a modulating factor. The net rate of synthesis of diatoxanthin depended both on the concentration of diadinoxanthin (its partner in the xanthophyll cycle) and on light, illustrating its photoprotective function in the xanthophyll cycle. In axenic strain L, the ratio of total fucoxanthins to chl a correlated strongly with photon flux density and can potentially be used to assess the physiological status with respect to irradiance in field populations. In multispecific bloom situations, the ratio of diadinoxanthin plus diatoxanthin to total fucoxanthins could be used as an alternative indicator for the light-dependent physiological state of E. huxleyi, provided that no other chromophytes are present. Application of these correlations to mesocosm data from the literature has so far provided no evidence that E. huxleyi blooms form only at inhibiting light levels, as previously suggested.
在分批培养中，对16种不同品系的赫氏颗石藻（Emiliania huxleyi (Lohm.) Hay et Mohler）色素组成的遗传变异进行了研究。在墨角藻黄素、19'-己酰氧基墨角藻黄素和19'-丁酰氧基墨角藻黄素的比例上发现了明显的品系依赖性差异，这妨碍了将这些单个色素用作物种水平的分类标记。然而，所有测试品系的总类胡萝卜素与叶绿素a的摩尔比是恒定的。此外，还对赫氏颗石藻的一个无菌品系（L）在光、硝酸盐和磷酸盐限制的连续培养中不同生长速率下的色素组成进行了定量分析。在所有条件下，墨角藻黄素和19'-己酰氧基墨角藻黄素密切相关。根据稳态速率计算，推测19'-己酰氧基墨角藻黄素是以光作为调节因子由墨角藻黄素合成的。二异丁基甲酮黄素的净合成速率既取决于二甲基丙烯基甲酮黄素（其在叶黄素循环中的伙伴）的浓度，也取决于光，这说明了其在叶黄素循环中的光保护功能。在无菌品系L中，总墨角藻黄素与叶绿素a的比例与光子通量密度密切相关，并有可能用于评估野外种群中关于辐照度的生理状态。在多物种水华情况下，只要不存在其他色素植物，二甲基丙烯基甲酮黄素加二异丁基甲酮黄素与总墨角藻黄素的比例可作为赫氏颗石藻光依赖生理状态的替代指标。到目前为止，将这些相关性应用于文献中的中宇宙数据，没有提供证据表明赫氏颗石藻水华仅在抑制光水平下形成，如先前所建议的那样。
