Keeling Patrick J, Brugerolle Guy
Department of Botany, Canadian Institute for Advanced Research, University of British Columbia, 3529-6270 University Blvd., Vancouver, BC, Canada V6T 1Z4.
Protist. 2006 Jun;157(2):205-12. doi: 10.1016/j.protis.2006.01.003. Epub 2006 Apr 18.
Octomitus intestinalis is a diplomonad flagellate inhabiting the digestive tract of rodents and amphibians. Octomitus is of evolutionary interest because, based on ultrastructural characteristics, it is thought to be closely related to the morphologically derived genus Giardia, and together they have been proposed to make up the Giardiinae. In molecular trees of diplomonads, Giardia is the deepest branching lineage, so identifying a sister group to Giardia that is less derived would be informative. Octomitus is a logical candidate for this position, but unfortunately there are no molecular data from it, and it is not available in culture. To determine the position of Octomitus, and specifically test whether it is more closely related to Giardia than other diplomonads, we have isolated it directly from the caecum of wild mice and characterized its small subunit ribosomal RNA (SSU rRNA) gene. Phylogenetic analysis showed Octomitus to be the sister to Giardia with strong support, together occupying one side of the deepest split in the diplomonad tree.
肠八鞭毛虫是一种双滴虫鞭毛虫，寄生于啮齿动物和两栖动物的消化道。八鞭毛虫在进化方面具有研究价值，因为基于超微结构特征，它被认为与形态学上衍生的贾第虫属密切相关，并且有人提议它们共同构成贾第亚科。在双滴虫的分子树中，贾第虫是分支最深的谱系，因此确定一个比贾第虫衍生程度更低的姐妹群将具有重要意义。八鞭毛虫是这个位置的合理候选者，但不幸的是没有它的分子数据，并且无法在培养物中获得。为了确定八鞭毛虫的位置，特别是测试它是否比其他双滴虫与贾第虫的关系更密切，我们直接从野生小鼠的盲肠中分离出它，并对其小亚基核糖体RNA（SSU rRNA）基因进行了表征。系统发育分析显示八鞭毛虫是贾第虫的姐妹群，得到了有力支持，它们共同占据了双滴虫树中最深分裂的一侧。
