Evolutionary adaptations and regulatory adjustments at the epithelial interface in the metaorganism Hydra

• Applicant: Professor Dr. Sebastian Fraune
• Subject Area: Evolution, Anthropology ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 536281046

Over evolutionary time, microbial communities colonizing a multicellular host evolved into integral components of host physiology and development. Investigating the underlying evolutionary processes is critical to understanding how bacteria influence the maintenance and fitness of metaorganisms. Here, we aim to answer the question of how and why bacteria form long-term associations with the ectodermal surfaces of aquatic hosts that are in constant contact with a wide variety of microbes. To this end, we will use the freshwater polyp Hydra and its main colonizer Curvibacter as a symbiosis model. The Betaproteobacteria Curvibacter is colonizing the mucus-like layer of the ectodermal epithelium of Hydra. It protects the host against fungal infection and influences key developmental processes. In preliminary recolonization experiments, we have already shown that native Curvibacter strains have a significant colonization advantage over non-native Curvibacter strains. Furthermore, meta-transcriptomic analyses show the high potential of Curvibacter to adjust its gene expression profile to host conditions, upregulating a large number of genes potentially involved in ROS mitigation. In this proposal, we will investigate the adaptation of Curvibacter to the Hydra epithelium at both the genomic and transcriptomic levels. On one hand a comparative genomic approach will be used to identify bacterial genes that diverged during Hydra and Curvibacter co-speciation and may mediate species-specific colonization. Using genetic approaches, we aim to study the function of identified genes in the context of host-bacteria interactions. On the other hand, we will use a time series of bacterial transcriptomes to examine the dynamic adjustments of Curvibacter during the establishment and maintenance of symbiosis with Hydra. Our aim is to identify and functionally characterize bacterial genes required for metabolic adaptations to the host habitat and involved in host-epithelial cross-talk. This experimental setup will reveal the adaptations of Curvibacter to the Hydra host habitat at both the genomic and transcriptomic levels, allowing us to functionally understand the intimate interaction at the molecular level. Overall, this will contribute to our understanding of how animal symbioses in the aquatic system have evolved and are maintained.

• DFG Programme: Research Grants