OCTOCORALs and their microbial symbionts
Unité de Recherche sur la Biologie des Coraux Précieux, Centre Scientifique de Monaco, Monaco
Research collaborators: Dr. Christine Ferrier-Pagès, Prof. Denis Allemand, Prof. Christian R. Voolstra (KAUST),
Dr. Howard Junca, Dr. Marzia Bo & Prof. Luigi Vezzulli (University of Genova), Laurent Ballesta
Research collaborators: Dr. Christine Ferrier-Pagès, Prof. Denis Allemand, Prof. Christian R. Voolstra (KAUST),
Dr. Howard Junca, Dr. Marzia Bo & Prof. Luigi Vezzulli (University of Genova), Laurent Ballesta
Gorgonian corals are important habitat-forming species of benthic communities from continental shelves to the deep sea. The 'animal forests' they form are true biodiversity hotspots. Unfortunately, anthropogenic pressures (e.g. climate change, pollution, fishing) cause severe degradation of coral reefs and gorgonian forests worldwide.
Symbioses with microbes are crucial for the health of the coral animal, as they provide nutrients and defense against pathogens, and increase coral's resilience to stress. While significant research effort has been dedicated to study the microbiota of tropical corals, very little is known about the microbes associated with gorgonian and scleractinian corals in temperate waters. This project investigated (1) the composition and stability of the microbiota of these corals, (2) evolutionary patterns between corals and their microbiota, and how offpsring |
Gorgonians from the Mediterranean Sea - Eunicella singularis, Leptogorgia sarmentosa and Corallium rubrum. The last is of commercial importance for the jewellery industry, but overexploitation is endangering populations significantly.
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establishes these symbioses, (3) the function of these microbes, (4) how the coral holobiont may be impacted by anthropogenic and environmental stressors, and (5) biotechnological applications related to the coral microbiota.
Results from this project have shown that the bacterial communities associated with Mediterranean gorgonians are dominated by a few bacterial species. While all soft gorgonians engage primarily in symbioses with bacteria from the genus Endozoicomonas, the red coral Corallium rubrum possesses a unique microbiome dominated by Spirochaetes. Interestingly, these gorgonian-microbe associations are highly stable on both spatial and temporal scales. This and the surprising overlap in the microbiota composition between various closely related coral species and major differences with more distantly related coral species suggested evolutionary links between octocorals and their microbiota. Currently, we are investigating (1) signals of phylosymbiosis and co-phylogeny in octocorals from the minimally impacted mesophotic zone (70-120m), and the transmission of symbionts between parent colony and offspring, (2) where the microbial symbionts are located within the coral tissues, and (3) the function of the gorgonian-associated bacteria within the holobiont and how this may be impacted by pollution and climate change using genomics, metagenomics and metatranscriptomics approaches.
Results from this project have shown that the bacterial communities associated with Mediterranean gorgonians are dominated by a few bacterial species. While all soft gorgonians engage primarily in symbioses with bacteria from the genus Endozoicomonas, the red coral Corallium rubrum possesses a unique microbiome dominated by Spirochaetes. Interestingly, these gorgonian-microbe associations are highly stable on both spatial and temporal scales. This and the surprising overlap in the microbiota composition between various closely related coral species and major differences with more distantly related coral species suggested evolutionary links between octocorals and their microbiota. Currently, we are investigating (1) signals of phylosymbiosis and co-phylogeny in octocorals from the minimally impacted mesophotic zone (70-120m), and the transmission of symbionts between parent colony and offspring, (2) where the microbial symbionts are located within the coral tissues, and (3) the function of the gorgonian-associated bacteria within the holobiont and how this may be impacted by pollution and climate change using genomics, metagenomics and metatranscriptomics approaches.
Nitrogen Cycling in The scleractinian coral holobiont
Centre Scientifique de Monaco, Monaco
Scleractinian corals form colonies with a hard calcium carbonate skeleton that together form coral reefs. Under normal conditions, the immune system of these corals is effective at regulating the microbiota and prevent disease (see Coral Immunology) and ensures that the holobiont maintains a healthy beneficial microbial community. Microbes may help the coral animal to defend against pathogens as well, but they are also involved in the nutrition of the host. Nitrogen, for example, is rare in oligotrophic waters where corals live and coral holobionts thus need to efficiently cycle and acquire nitrogen in order to grow. By combining analyses of the microbial community, stable nitrogen and carbon isotope assimilation and physiological measurements, the cycling and fixation of nitrogen in corals was
Model on the importance of endolytic diazotrophs for the survival of Oculina patagonica affected by temperature-induced bleaching
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investigated. Tropical scleractinian and soft corals in the Red Sea seemed to rely primarily on feeding on plankton or nitrogen-fixing bacteria (diazotrophs), or the assimilation of inorganic nitrogen compounds by algal symbionts for their nitrogen needs, but fixing of nitrogen by diazotroph symbionts appears to play a negligent role. In contrast, the coral Oculina patagonica benefits significantly from diazotrophs living in its skeleton. During summer, these corals may bleach, loosing their nutrition provided by the algal symbionts. However, the endolytic diazotrophs then translocate nitrogen to algae in the coral's skeleton that then proliferate and feed the coral animal, ensuring its survival under high stress conditions that may otherwise be fatal.
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