Towards understanding an ultimately simple metaorganism: impact of symbiotic microbes and algae on developmental processes of Hydra and their adaption within the host

Inter-species interactions in the freshwater polyp Hydra between symbiotic algae and host cells had been the subject of research since decades since they not only provide insights into the basic “tool kit” necessary to establish symbiotic interactions, but are also of relevance in understanding the resulting evolutionary selection processes. A long term persistence of symbiotic associations is prevalent not only in two-party interactions of Hydra and symbiotic algae, but also in more complex systems including stable associated bacteria. Studying symbiotic inter-species interactions in Hydra, therefore, may be a paradigmatic example of a complex symbiotic community that influences the host´s health and development. Starting from one of “the” classical model systems in developmental biology, we used Hydra in the last few years to explore host-microbe interactions. Our findings reveal that epithelia and components of the innate immune system play an active role in selecting the inhabitant microbiota via a complex genetic network. The work has contributed to a paradigm shift in evolutionary immunology:

Components of the innate immune system with its host-specific antimicrobial peptides appear to have evolved in early branching metazoans because of the need to control the resident beneficial microbes rather than because of invasive pathogens. Yet in spite of all these insights in an ultimately simple metaorganism we have still not been able to coherently integrate the accumulated abundance of information into a truly mechanistic understanding of host-microbe interactions. To understand common principles of symbiogenesis and their links to metaorganism evolution, we examine the impact of symbiotic microbes and algae on developmental processes in Hydra.

Elucidating these issues will not only contribute to our understanding of the genetic basis of microbial speciation and adaptation within eukaryotic hosts but will also provide conceptual insights into the impact of beneficial microbes on the host life history and the complexity of host-microbe interactions in general.


Jay Bathia

PhD Candidate
Kiel University Zoological Institute

Dr. Peter Deines

Postdoctoral Researcher, Associated Junior Researcher
Kiel University Zoological Institute

Risa Taira

PhD Candidate, Alumni
Kiel University Zoological Institute

Jinru He

PhD Candidate
Kiel University Zoological Institute



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