Barcytė Dovilė, Hodač Ladislav, Nedbalová Linda, Elster Josef
Department of Ecology, Faculty of Science, Charles University, Viničná 7, Prague 2, 128 44, Czech Republic.
Department of Systematics, Biodiversity and Evolution of Plants (with Herbarium), Georg-August-University of Göttingen, Untere Karspüle 2, Göttingen, 37073, Germany.
Int J Syst Evol Microbiol. 2018 Mar;68(3):851-859. doi: 10.1099/ijsem.0.002595. Epub 2018 Feb 1.
With the advent of molecular phylogenetic methods, it has become possible to assess the bioversity of snow algae more accurately. In this study, we focused on a morphological, ultrastructural and taxonomic description of a new Chloromonas-like alga isolated from snow in the High Arctic (Svalbard). Light and transmission electron microscopy revealed broad ellipsoidal or ellipsoidal-cylindrical, occasionally spherical cells with a chloroplast without a pyrenoid, an inconspicuous eyespot and a papilla. The size difference and the aforementioned morphological traits clearly distinguished the alga from its closest counterparts within the genus Chloromonas. Moreover, we were able to cultivate the alga at both 5 and 20 °C, revealing the psychrotolerant nature of the strain. Phylogenetic analyses of the plastid rbcL and nuclear 18S rRNA gene showed that the alga is nested within a clade containing a number of psychrotolerant strains within the Chloromonadinia phylogroup (Chlorophyceae). In the rbcL phylogeny, the alga formed an independent lineage, sister to the freshwater species Chloromonas paraserbinowii. Comparisons of secondary structure models of a highly variable ITS2 rDNA marker showed support for a distinct species identity for the new strain. The ITS2 secondary structure of the new isolate differed from the closest matches 'Chlamydomonas' gerloffii and Choloromonas reticulata by three and five compensatory base changes, respectively. Considering the morphological and molecular differences from its closest relatives, a new psychrotolerant species from the Arctic, Choromonas arctica sp. nov., is proposed.
随着分子系统发育方法的出现，更准确地评估雪藻的生物多样性成为可能。在本研究中，我们着重对从北极地区（斯瓦尔巴群岛）雪地分离出的一种新的似绿藻属藻类进行了形态学、超微结构和分类学描述。光学显微镜和透射电子显微镜显示，该藻细胞呈宽椭圆形或椭圆 - 圆柱形，偶尔呈球形，有一个无蛋白核的叶绿体、一个不明显的眼点和一个乳头状突起。大小差异以及上述形态特征明显将该藻与其在绿藻属中最相近的种类区分开来。此外，我们能够在5℃和20℃下培养该藻，这揭示了该菌株的耐低温特性。对质体rbcL和核18S rRNA基因的系统发育分析表明，该藻嵌套在绿藻门绿藻纲绿藻目绿藻科绿藻属的一个包含许多耐低温菌株的进化枝内。在rbcL系统发育树中，该藻形成一个独立的谱系，是淡水物种副塞尔比诺绿藻的姐妹种。对高度可变的ITS2 rDNA标记二级结构模型的比较显示，支持新菌株具有独特的物种身份。新分离株的ITS2二级结构与最相近的匹配种“gerloffii衣藻”和网状绿藻分别有三个和五个补偿性碱基变化。考虑到与其最亲近亲属的形态和分子差异，我们提出了一种来自北极的新的耐低温物种——北极绿藻。
