Discovery of ectosymbiotic Endomicrobium lineages associated with protists in the gut of stolotermitid termites
Discovery of ectosymbiotic Endomicrobium lineages associated with protists in the gut of stolotermitid termites
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DOI：
10.1111/1758-2229.12549
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发表时间：
2017-08-01
影响因子：
3.3
通讯作者：
Hongoh, Yuichi
中科院分区：
文献类型：
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作者：
Izawa, Kazuki;Kuwahara, Hirokazu;Hongoh, Yuichi
内微菌属是低等白蚁肠道中的优势菌群，大多数内微菌属是肠道原生生物的细胞内共生菌。在这里，我们报告的发现内微菌外共生白蚁肠道原生生物。结果发现，在维多利亚土白蚁螺菌体原生生物细胞表面附着有刚毛状的内微菌细胞。透射电子显微镜显示，一个假定的内微菌属细胞可能通过从细菌尖端的突起附着在原生生物表面。在白蚁Porotermes adamsoni肠道中的原生生物Trichonympha magna的细胞表面上也发现了一种与螺菌原生生物的Endomicrobium外共生菌具有98.9% 16S rRNA序列同一性的Escherichia型。我们提出了新的物种endatus Endomicrobium superficiale'为这些细菌。T. magna的16SrRNA序列与Ca.表面内微菌此外，在阿氏肺吸虫肠道中的螺旋毛状菌类原生生物与可能附着在宿主鞭毛上的内微菌属（Endomicrobium）相关。系统发育分析表明，这些外共生谱系已经从自由生活的内微生物谱系进化了多次，并且与内共生体相对较远。我们的研究结果提供了新的见解的生态和进化的内微菌。
The genus Endomicrobium is a dominant bacterial group in the gut of lower termites, and most phylotypes are intracellular symbionts of gut protists. Here we report the discovery of Endomicrobium ectosymbionts of termite gut protists. We found that bristle-like Endomicrobium cells attached to the surface of spirotrichosomid protist cells inhabiting the termite Stolotermes victoriensis. Transmission electron microscopy revealed that a putative Endomicrobium cell likely attached to the protist surface via a protrusion from the tip of the bacterium. A phylotype, sharing 98.9% 16S rRNA sequence identity with the Endomicrobium ectosymbionts of the spirotrichosomid protists, was also found on the cell surface of the protist Trichonympha magna in the gut of the termite Porotermes adamsoni. We propose the novel species Candidatus Endomicrobium superficiale' for these bacteria. T. magna simultaneously harboured another Endomicrobium ectosymbiont that shared 93.5-94.2% 16S rRNA sequence identities with Ca. Endomicrobium superficiale'. Furthermore, Spirotrichonympha-like protists in P. adamsoni guts were associated with an Endomicrobium phylotype that possibly attached to the host flagella. A phylogenetic analysis suggested that these ectosymbiotic lineages have evolved multiple times from free-living Endomicrobium lineages and are relatively distant from the endosymbionts. Our results provide novel insights into the ecology and evolution of the Endomicrobium.