Department of Biology, and Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada.
Department of Biochemistry, and Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada.
J Eukaryot Microbiol. 2024 Nov-Dec;71(6):e13048. doi: 10.1111/jeu.13048. Epub 2024 Sep 3.
Metamonads are a large and exclusively anaerobic group of protists. Additionally, they are one of the three clades proposed to ancestrally possess an "excavate" cell morphology, with a conspicuous ventral groove accompanied by a posterior flagellum with a vane. Here, we cultivate and characterize four anaerobic bacterivorous flagellates from hypersaline and alkaline soda lake environments, which represent a novel clade. Small subunit ribosomal RNA (SSU rRNA) gene phylogenies support recent phylogenomic analyses in placing them as the sister of barthelonids, a group that is itself sister to or deeply branching within Fornicata (Metamonada). The new isolates have a distinctive morphology: the hunchbacked cell body is traversed by a narrow ventral groove ending in a large opening to a conspicuous recurrent cytopharynx. The right margin of the groove is defined by a thin "lip." The posterior flagellum bears a wide ventral-facing vane. The narrow ventral groove and elongate cytopharynx are shared with barthelonids. We describe one isolate as Skoliomonas litria, gen. et sp. nov. Further investigation of their mitochondrial-related organelles (MROs) and detailed ultrastructural studies would be important to understanding the adaptation to anaerobic conditions in Metamonads-especially fornicates-as well as the evolution of the "excavate" cell architecture.
变形体是一类大型且专性厌氧的原生生物。此外，它们是被提议的三个祖先具有“挖掘”细胞形态的进化枝之一，具有明显的腹侧沟和带有叶片的后鞭毛。在这里，我们从高盐和碱性苏打湖环境中培养和描述了四种厌氧食细菌鞭毛虫，它们代表了一个新的进化枝。小亚基核糖体 RNA（SSU rRNA）基因系统发育支持最近的基因组分析，将它们置于 barthelonids 的姐妹进化枝中，而 barthelonids 本身又是 Fornicata（变形体）的姐妹进化枝或深分支。新的分离株具有独特的形态：驼背的细胞体被一条狭窄的腹侧沟穿过，该沟在一个大开口处终止于一个明显的反复出现的胞咽。沟的右边缘由一个薄的“唇”定义。后鞭毛带有一个宽大的面向腹侧的叶片。狭窄的腹侧沟和细长的胞咽与 barthelonids 共享。我们将一个分离株描述为 Skoliomonas litria，gen. et sp. nov. 进一步研究它们的线粒体相关细胞器（MRO）和详细的超微结构研究对于理解变形体（尤其是 fornicates）在厌氧条件下的适应以及“挖掘”细胞结构的进化将非常重要。
