Darienko Tatyana, Rad-Menéndez Cecilia, Pröschold Thomas
Research Department for Limnology, Leopold-Franzens-University of Innsbruck, A-5310 Mondsee, Austria.
Department of Applied Bioinformatics, Institute for Microbiology and Genetics, Georg-August-University of Göttingen, D-37077 Göttingen, Germany.
Microorganisms. 2024 Aug 6;12(8):1604. doi: 10.3390/microorganisms12081604.
Traditionally, the order Ulotrichales comprised green algae of an unbranched, uniseriate, filamentous morphology. However, since the establishment of ultrastructural features, the circumscription of this order has dramatically changed. Some genera and species have been excluded from this order and others with different morphologies (sarcinoid, branched filaments or even parenchymatous taxa) have been included. Phylogenetic analyses have confirmed the monophyly of this order, but its differentiation from the Ulvales and Acrosiphoniales remains difficult because of the lack of synapomorphies at every level (morphology, molecular signatures). To demonstrate the difficulties of placement into genera and orders, we investigated two sarcinoid taxa with the absence of zoospore formation. SSU and ITS rDNA tree topology and the ITS-2/CBC approach revealed that both strains SAG 2661 and CCAP 312/1 belong to and the newly erected genus , respectively. The species conception using this approach was evaluated by sequencing the plastid-coding gene A, a commonly used barcode marker for green algae. All three molecular markers resulted in similar topologies at the generic and species levels, which is consistent with the ITS-2/CBC approach and A for barcoding. The reevaluation of the ultrastructural features revealed that the presence of organic scales on the surfaces of motile cells is characteristic for the order Ulotrichales and can be used for separation from the closely related orders. As a consequence of our study, we propose the new genus for strain CCAP 312/1.
传统上，丝藻目包含形态为不分枝、单列丝状的绿藻。然而，自超微结构特征确立以来，该目的界定发生了巨大变化。一些属和物种已被排除在该目之外，而其他具有不同形态（类球菌状、分枝丝状甚至薄壁组织类群）的属和物种被纳入其中。系统发育分析证实了该目的单系性，但由于在各个层面（形态学、分子特征）缺乏共衍征（共同衍生特征），其与石莼目和顶管藻目的区分仍然困难。为了说明分类到属和目的困难，我们研究了两个不形成游动孢子的类球菌状类群。小亚基核糖体RNA（SSU rDNA）和内转录间隔区（ITS）rDNA树的拓扑结构以及ITS - 2/ CBC方法表明，菌株SAG 2661和CCAP 312/1分别属于新建立的属 。通过对质体编码基因A进行测序来评估使用这种方法的物种概念，质体编码基因A是绿藻常用的条形码标记。所有这三个分子标记在属和种水平上都产生了相似的拓扑结构，这与ITS - 2/ CBC方法以及用于条形码分析的基因A一致。对超微结构特征的重新评估表明，运动细胞表面存在有机鳞片是丝藻目的特征，可用于与近缘目区分开来。作为我们研究的结果，我们为菌株CCAP 312/1提出了新属 。
