Karpov Serguei A, Bass David, Mylnikov Alexander P, Cavalier-Smith Thomas
Department of Zoology, Herzen State Pedagogical University of Russia, Moika emb. 48, 191186 St. Petersburg, Russian Federation.
Protist. 2006 Jun;157(2):125-58. doi: 10.1016/j.protis.2006.01.001. Epub 2006 May 2.
Cercomonads are among the most abundant and widespread zooflagellates in soil and freshwater. We cultured 22 strains and report their complete 18S rRNA sequences and light microscopic morphology. Phylogenetic analysis of 51 Cercomonas rRNA genes shows in each previously identified major clade (A, B) two very robust, highly divergent, multi-species subclades (A1, A2; B1, B2). We studied kinetid ultrastructure of five clade A representatives by serial sections. All have two closely associated left ventral posterior microtubular roots, an anterior dorsal root, a microtubule-nucleating left anterior root, and a cone of microtubules passing to the nucleus. Anterior centrioles (=basal bodies, kinetosomes) of A1 have cartwheels; the posterior centriole does not, suggesting it is older, and implying flagellar transformation similar to other bikonts. Strain C-80 (subclade A2) differs greatly, having a dorsal posterior microtubule band, but lacking the A1-specific fibrillar striated root, nuclear extension to the centrioles, centriolar diaphragm, extrusomes; both mature centrioles lack cartwheels. For clade A2 we establish Eocercomonas gen. n., with type Eocercomonas ramosa sp. n., and for clade B1 Paracercomonas gen. n. (type Paracercomonas marina sp. n.). We establish Paracercomonas ekelundi sp. n. for culture SCCAP C1 and propose a Cercomonas longicauda neotype and Cercomonas (=Neocercomonas) jutlandica comb. n. and Paracercomonas (=Cercomonas) metabolica comb. n.
圆纤毛虫是土壤和淡水中数量最多、分布最广的动鞭毛虫之一。我们培养了22个菌株，并报告了它们完整的18S rRNA序列和光学显微镜形态。对51个圆纤毛虫rRNA基因的系统发育分析表明，在每个先前确定的主要进化枝（A、B）中，有两个非常稳健、高度分化的多物种亚进化枝（A1、A2；B1、B2）。我们通过连续切片研究了进化枝A的五个代表的动质体超微结构。所有样本都有两个紧密相连的左腹后微管根、一个前背根、一个微管成核的左前根，以及一个通向细胞核的微管锥。A1的前中心粒（=基体、动基体）有车轮状结构；后中心粒没有，这表明它更古老，意味着鞭毛转化与其他双鞭毛生物相似。菌株C-80（亚进化枝A2）差异很大，有一个背后微管带，但缺少A1特有的纤维状横纹根、细胞核延伸至中心粒、中心粒隔膜、射出体；两个成熟的中心粒都没有车轮状结构。对于进化枝A2，我们建立了新属Eocercomonas，模式种为Eocercomonas ramosa sp. n.，对于进化枝B1建立了新属Paracercomonas（模式种为Paracercomonas marina sp. n.）。我们为培养物SCCAP C1建立了新种Paracercomonas ekelundi sp. n.，并提出了长尾圆纤毛虫的新模式，以及圆纤毛虫（=新圆纤毛虫）jutlandica的新组合和Paracercomonas（=圆纤毛虫）metabolica的新组合。
