| 研究開始時の研究の概要 |
My research will shed light on the interaction between corallicolids and zooxanthellae, the two most common protists associated with corals. This will also help to improve the management of coral reefs, for example, in relation to the monitoring and forecast of coral ‘bleaching’ events with zooxanthellae expulsion. These results will have a substantial impact on the knowledge of the scientific community on the evolutionary transition from free-living autotrophs to parasites. Several peer-reviewed manuscripts will be published in international journals with open-access.
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| 研究実績の概要 |
I sequenced and analyzed the symbionts of over 100 coral samples from Okinawa and 16 regions worldwide. Our results clarified their global distribution, as well as their localization in the coral tissues. For instance, Sanger sequencing of the 18S-rRNA gene region of corallicolids showed that coral species from Japan are associated with the same lineage, and this same corallicolid clade is also symbiotic with coral species from different Hawai’i and the Caribbean Sea.
Additionally, our results with amplicon sequencing (16S, 18S, and ITS2) indicated global patterns of coral-symbiont diversity. The predominant bacteria phylum associated with coral samples worldwide was Proteobacteria, such as the mutualistic Endozoicomonas and the pathogenic Vibrios. As expected, the most abundant eukaryote associated with coral colonies was Dinoflagellate, especially zooxanthellae of Cladocopium, followed by Durisdinium. A few samples were also associated with lineages of Symbiodinium, mostly restricted to the Atlantic Ocean. Other common microeukaryotes were apicomplexans of corallicolids, chromerids, and Fungi. Furthermore, our results indicated that corallicolids were more abundant in samples from the Atlantic Ocean compared to the Indo-Pacific Ocean, including Okinawa.
Our metagenomic and genomic results confirmed the high diversity of coral microbes. Moreover, we reported a potentially undescribed bacteria species of the genus Spiroplasma, and its genes indicated that this might be a mutualistic symbiont.
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