Department of Biology, Middle Tennessee State University, P. O. Box 60, Murfreesboro, Tennessee 37132, USA.
J Eukaryot Microbiol. 2013 Jul-Aug;60(4):399-405. doi: 10.1111/jeu.12050. Epub 2013 Jun 4.
Sterols are a class of membrane-reinforcing, ringed lipids which have a long history of examination in algae as a means of deriving chemotaxonomic relationships and as potential lipidic biomarkers. The Raphidophyceae represent a class of harmful, bloom-forming, marine and freshwater algae. To date, there have been four published examinations of their sterol composition, focusing primarily on brown-pigmented, marine species within the genera, Chattonella, Fibrocapsa, and Heterosigma. Lacking in these examinations has been the species Gonyostomum semen Ehrenb., which is a green-pigmented, freshwater raphidophyte with a worldwide distribution. The goal of this study was to examine the sterol composition of this nuisance alga, determine the potential of using its sterol profile as a biomarker, and finally to determine if there is any intraspecific variability between isolates. We have examined 21 isolates of G. semen from a number of Scandinavian lakes, and all were found to produce two major sterols, 24-ethylcholesta-5,22E-dien-3β-ol and 24-ethylcholest-5-en-3β-ol, and 24-methylcholest-5-en-3β-ol as a minor sterol; the presence of 24-ethylcholesta-5,22E-dien-3β-ol differentiates G. semen from brown-pigmented, marine raphidophytes which generally lack it. The results of this study indicate that isolates of G. semen from geographically separate lakes across Finland and Scandinavia have the same sterol biosynthetic pathway, and that there is no evolutionary divergence between the isolates with regard to sterol composition. The sterols of G. semen are not considered to be useful biomarkers for this particular organism because they are commonly found in other algae and plants.
甾醇是一类增强膜稳定性的环状脂质，在藻类中作为一种衍生化学分类关系和潜在脂质生物标志物的手段，具有悠久的研究历史。红藻门是一类有害的、形成水华的海洋和淡水藻类。迄今为止，已经有四份关于其甾醇组成的出版物，主要集中在属中的棕色色素、海洋种，如 Chattonella、Fibrocapsa 和 Heterosigma。这些研究中缺乏的是绿色素、淡水红藻属 Gonystomum semen Ehrenb.，该种在全球范围内分布。本研究的目的是检查这种有害藻类的甾醇组成，确定其甾醇特征作为生物标志物的潜力，并最终确定分离株之间是否存在种内变异性。我们检查了来自许多斯堪的纳维亚湖泊的 21 株 G. semen，发现它们都产生两种主要甾醇，24-乙基胆甾-5,22E-二烯-3β-醇和 24-乙基胆甾-5-烯-3β-醇，以及 24-甲基胆甾-5-烯-3β-醇作为次要甾醇；24-乙基胆甾-5,22E-二烯-3β-醇的存在将 G. semen 与通常缺乏它的棕色色素、海洋红藻区分开来。本研究结果表明，来自芬兰和斯堪的纳维亚各地地理分离湖泊的 G. semen 分离株具有相同的甾醇生物合成途径，并且在甾醇组成方面，分离株之间没有进化分歧。G. semen 的甾醇不被认为是该特定生物的有用生物标志物，因为它们通常存在于其他藻类和植物中。
