CRASSOBIOM: "The function and interactions between the Pacific oyster and its microbiota in relation to oyster performance in extreme habitats"

Supervisor: Prof. Dr. Inna Sokolova (URO); Prof. Dr. Matthias Labrenz (IOW); Dr. Mathias Wegner (AWI)

Deutsche Forschungsgemeinschaft (DFG)

Laufzeit: 01.06.2020 - 31.05.2023

Extreme environments can select for mutualistic interactions between animals and their microbiota which are beneficial and often vital for the survival of the holobionts (i.e. the organized biological units composed of the host and associated microbes). The intertidal zone is an extremely stressful environment with frequent fluctuations in abiotic factors including temperature, salinity, oxygen and desiccation stress. Survival under these harsh environmental conditions requires a high degree of adaptability and stress tolerance. The Pacific oyster, Crassostrea gigas, has successfully colonized intertidal habitats worldwide often outperforming native species. The reasons for this remarkable ecological success of C. gigas under the extreme conditions of the intertidal zone are not yet fully understood.

The proposed study will test the hypothesis that the interaction of C. gigas with its microbiota may facilitate the survival of oysters under the extremely variable and stressful conditions of the intertidal zone of the German Wadden Sea, where oysters invaded in the early 1990ies and established dense populations of >3000 individual per m2. Laboratory studies will be used to assess the role of oyster microbiome in the hosts’ stress tolerance by determining the effects of temperature, salinity and hypoxic stress on the physiology, immune functions and molecular stress responses in the hosts with intact and depleted microbiomes. Microbial diversity will be assessed using 16S metabarcoding, and the holobionts’ samples that show the strongest correlated change in the host response and microbiome composition will be used in metatranscriptomic analysis to identify the potential microbial pathways contributing to the host fitness under stress conditions. A long-term field transplant experiment in the German Wadden Sea will be conducted to determine whether the molecular stress signatures of the host-microbiome interactions can be tracked in the natural habitats with the different degree of abiotic stress. We will analyse physiological stress (using bioenergetics and immune biomarkers and stress-induced transcriptome profiles) in oysters that remained in their native habitats and those transplanted for a year between the intertidal and subtidal zones. Simultaneously, the shifts in the taxonomic and functional diversity of oyster-associated microbiota will be assessed in the native and transplanted oysters to test for potential coordinated functional responses of the microbiota and the hosts during acclimation to novel habitats. Integration of the data from the laboratory and field studies would provide mechanistic insights into the links between host physiology and microbiome diversity and function, and the potential role of host-microbiome interplay in the holobiont’s ecological success in the stressful intertidal environments of the Wadden Sea.