Symbiotic communication of octocoral, Eleutherobia rubra responding to environmental stress

Abstract

Corals are one of the biologically diverse marine ecosystems providing important habitats for marine life. Every coral has a complex cluster of microbes including symbiotic flagellates, bacteria, archaea, and fungi. Most of coral studies are about symbiotic corals and they focused on the relationship between symbiotic algae and host corals. In this study, we selected non-symbiotic coral, Eleutherobia rubra, belonging to the phylum Cnidaria, class Anthozoa, and order Alcyonacea as the target species. This coral is an azooxanthellate octocoral and particularly found in the East, West, and South Seas around the Korean Peninsula. In this study we collected E. rubraand exposed to various seawater temperature (26, 28 and 30ºC) to compare the composition of bacterial community using the Next Generation Sequencing technique. The results showed total 88 species of bacteria were found in E. rubra in wild condition and they were classified to 72 genus, 41 family, 32 order, 16 class and 13 phylum. Soft coral, E. rubra were enriched in OTUs from the families Hahellaceae, Mycoplasmataceae, Alteromonadaceae, Anaplasmataceae, and Rhodobacteraceae. The number of bacteria species belong to following 8 families, Flavobacteriaceae, Bacillaceae, Comamonadaceae, Alteromonadaceae, Pseudoalteromonadaceae, Hahellaceae, Pseudomonadaceae and Vibrionaceae robustly increased in responses to the heat stress in 26, 28 and 30ºC groups and the species Mesoflavibacter sabulilitoris, Vibrio tubiashii, Pseudomonas azotoformans, Oceanospirillum beijerinckii, Neptuniibacter Caesariensis, and Amphritea spongicola showed proportionally increase by temperature. The number of Endozoicomonas elysicola showed an increase up to 26ºC then decrease in 28 and 30ºC groups. This study described bacterial composition changes and comparison between the thermal stressed group of E. rubra and the control group, and also the bacterial composition changes in coral habitat seawater under seasonal variation. This study was supported by KIOST PM62830 and NRF (2020R1A2B5B02001619).