| Date |
Feb 28, 2017 |
| Speaker |
PhD student, Kazuki Izawa, Postdoctoral researcher at Department of Biological Sciences, Tokyo Institute of Technology, Japan
|
| Title |
Endomicrobium endosymbionts of termite-gut protists have functional defense systems
against bacteriophages
|
| Abstract |
The genus Endomicrobium is a dominant bacterial group in the gut of basal termite lineages, and the majority are
intracellular symbionts of gut cellulolytic protists. “Candidatus Endomicrobium trichonymphae” phylotype Rs-D17
(genomovar Ri2008) is the first genome-analysed endosymbiotic Endomicrobium. The Rs-D17 genome is small (ca. 1.1
Mb) and contains many pseudogenes; it is in the course of genome reduction (Hongoh et al., 2008, PNAS). Based on the
genome analysis, it has been suggested that the endosymbiont synthesise and provides essential nitrogen compounds to the
host protist and termite.
Here, we newly reconstructed four genomes of endosymbiotic Endomicrobium species including another genomovar of
Rs-D17 (genomovar Ti2015). Interestingly, all the Endomicrobium genomes contained apparently intact restriction-
modification (R-M) systems among numerous pseudogenized ones. In addition, the genomes possessed multiple
CRISPR/Cas systems. At least one of these CRISPR/Cas systems is most likely functional because the “spacer” sequences
were completely different between the two genomovars Ri2008 and Ti2015, while the “repeat” sequences were identical
(Izawa et al., 2016, GBE). Furthermore, the spacer sequences of CRISPR/Cas systems of another Endomicrobium
endosymbiont were identical to bacteriophage contigs obtained during our viral metagenomic analysis of the termite-gut
microbiota. Our results indicate that endosymbiotic Endomicrobium are attacked by bacteriophages in spite of their
obligately intracellular lifestyle.
|
|
アブストラクト