Murakami Takumi, Segawa Takahiro, Dial Roman, Takeuchi Nozomu, Kohshima Shiro, Hongoh Yuichi
Department of Biological Sciences, Tokyo Institute of Technology.
Microbes Environ. 2017 Mar 31;32(1):32-39. doi: 10.1264/jsme2.ME16158. Epub 2017 Mar 9.
The community structure of bacteria associated with the glacier ice worm Mesenchytraeus solifugus was analyzed by amplicon sequencing of 16S rRNA genes and their transcripts. Ice worms were collected from two distinct glaciers in Alaska, Harding Icefield and Byron Glacier, and glacier surfaces were also sampled for comparison. Marked differences were observed in bacterial community structures between the ice worm and glacier surface samples. Several bacterial phylotypes were detected almost exclusively in the ice worms, and these bacteria were phylogenetically affiliated with either animal-associated lineages or, interestingly, clades mostly consisting of glacier-indigenous species. The former included bacteria that belong to Mollicutes, Chlamydiae, Rickettsiales, and Lachnospiraceae, while the latter included Arcicella and Herminiimonas phylotypes. Among these bacteria enriched in ice worm samples, Mollicutes, Arcicella, and Herminiimonas phylotypes were abundantly and consistently detected in the ice worm samples; these phylotypes constituted the core microbiota associated with the ice worm. A fluorescence in situ hybridization analysis showed that Arcicella cells specifically colonized the epidermis of the ice worms. Other bacterial phylotypes detected in the ice worm samples were also abundantly recovered from the respective habitat glaciers; these bacteria may be food for ice worms to digest or temporary residents. Nevertheless, some were overrepresented in the ice worm RNA samples; they may also function as facultative gut bacteria. Our results indicate that the community structure of bacteria associated with ice worms is distinct from that in the associated glacier and includes worm-specific and facultative, glacier-indigenous lineages.
通过对16S rRNA基因及其转录本进行扩增子测序，分析了与冰川冰虫（Mesenchytraeus solifugus）相关的细菌群落结构。从阿拉斯加的两个不同冰川——哈丁冰原和拜伦冰川采集了冰虫，并对冰川表面进行了采样以作比较。在冰虫样本和冰川表面样本的细菌群落结构中观察到了显著差异。几乎仅在冰虫中检测到了几种细菌系统型，这些细菌在系统发育上隶属于与动物相关的谱系，或者有趣的是，隶属于主要由冰川本土物种组成的进化枝。前者包括属于柔膜菌纲、衣原体纲、立克次氏体目和毛螺菌科的细菌，而后者包括Arcticella和Herminiimonas系统型。在冰虫样本中富集的这些细菌中，柔膜菌纲、Arcticella和Herminiimonas系统型在冰虫样本中被大量且持续地检测到；这些系统型构成了与冰虫相关的核心微生物群。荧光原位杂交分析表明，Arcticella细胞特异性地定殖在冰虫的表皮上。在冰虫样本中检测到的其他细菌系统型也从各自的栖息地冰川中大量回收；这些细菌可能是冰虫消化的食物或临时居民。然而，有些在冰虫RNA样本中占比过高；它们也可能作为兼性肠道细菌发挥作用。我们的结果表明，与冰虫相关的细菌群落结构与相关冰川中的不同，包括特定于冰虫的和兼性的、冰川本土的谱系。
