Endosymbiosis between coccoid green algae and ciliates are widely distributed and occur in various phylogenetic lineages among the Ciliophora. Most mixotrophic ciliates live in symbiosis with different species and genera of the so-called Chlorella clade (Trebouxiophyceae). The mixotrophic ciliates can be differentiated into two groups: (i) obligate, which always live in symbiosis with such green algae and are rarely algae-free and (ii) facultative, which formed under certain circumstances such as in anoxic environments an association with algae. A case of the facultative endosymbiosis is found in the recently described species of Tetrahymena, T. utriculariae, which lives in the bladder traps of the carnivorous aquatic plant Utricularia reflexa. The green endosymbiont of this ciliate belonged to the genus Micractinium. We characterized the isolated algal strain using an integrative approach and compared it to all described species of this genus. The phylogenetic analyses using complex evolutionary secondary structure-based models revealed that this endosymbiont represents a new species of Micractinium, M. tetrahymenae sp. nov., which was further confirmed by the ITS2/CBC approach.

中文翻译：

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从纤毛虫中分离出的一种新的内生菌四膜膜菌（Trebouxiophyceae，Chlorophyta）

球状藻类和纤毛虫之间的内共生分布广泛，并在纤毛虫的各种系统发育谱系中发生。大多数混养的纤毛虫与不同种类和属的小球藻进化枝（Trebouxiophyceae）共生。混合营养的纤毛虫可分为两类：（i）专性的，总是与这样的绿藻共生，很少不含藻类；（ii）兼性的，在某些情况下形成的，例如在缺氧环境中与藻类结合。在最近描述的四膜虫（T. utriculariae）物种中发现了一例兼性内共生病例，该物种生活在食肉水生植物Utricularia reflexa的膀胱诱捕器中。。该纤毛虫的绿色内共生菌属于Micractinium属。我们使用整合方法对分离的藻株进行了表征，并将其与该属的所有描述种进行了比较。使用复杂的基于进化二级结构的模型进行的系统发育分析表明，这种内共生体代表了一种新的麦哲伦菌，四膜膜菌。十一月，这被ITS2 / CBC方法进一步证实。