The individual as metaorganism

Multicellular organisms exist as metaorganisms comprised of the macroscopic host and synergistic inteholobiontrdependence with numerous microbial and eukaryotic species. Health is fundamental multi-organismal. The Bosch lab studies the intricate interactions within metaorganisms in a simple model system, the cnidarian Hydra.

Cnidarians represent a key transition in the evolution of animal complexity, and are therefore critical to understand not only the origins of developmental mechanisms and their role in more complex organisms including humans but also the impact of environmental factors such as microbial interactions on host performance.

To gain an understanding of the evolution of immunity, we study the innate immune system in Hydra and the molecular interactions between microbes and host (Hydra) cells that promote normal development and homeostasis. We hypothesize that components of the innate immune system with its host specific antimicrobial peptides and a rich repertoire of pattern recognition receptors evolved in early branching metazoans because of the need to control the resident beneficial microbes rather than because of invasive pathogens.

Based on observations in transgenic Hydra with altered expression levels of stem cell transcription factors, we also propose a mutual intertwining between the stem cell regulatory machinery of the host and the resident microbiota composition, such that disturbances in either trigger a restructuring and resetting of the other.

Finally, we recognize evolution as a basic science for medicine. Diseases which affect barrier organs (, intestine) often develop from the interaction between microbes and individual genetic susceptibility. Health is fundamental multi-organismal. Using a combined bioinformatics and high throughput genomics approach, we investigate the evolution and function of orthologs to human disease genes for barrier dysfunction in Hydra.


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Video: A Brief introduction to the lab and our recent research

Why we chose the biologically immortal Hydra as organism of study, and how clues from its genes could help to unravel the mechanisms behind human ageing


The increasing realization that animals exist only within a partnership with symbionts has led to three important realizations.

  • First, it is becoming increasingly clear that to understand the physiology, evolution and development of a given species, we cannot study the species in isolation.
  • Second, the health and fitness of animals, including humans, appears to be fundamentally multi-organismal. Disturbance within the complex community can have drastic consequences for the well-being of the members.
  • Finally, the holobiont may be an important unit of evolutionary selection, a selection of “teams” containing many genomes and species.

Recent news

We communicate all our observations and results directly to the public in our news section.

Recent publications


Satiety controls behavior in Hydra through an interplay of pre-enteric and central nervous system-like neuron populations

Giez C, Noack C , Sakib E, Hofacker L-M , Repnik U, Bramkamp M , Bosch TCG (2024)  Satiety controls behavior in Hydra through an interplay of pre-enteric and central nervous system-like neuron populations. Cell Reports, 43, June 25, 2024 DOI:10.1016/j.celrep.2024.114210



The potential importance of the built-environment microbiome and its impact on human health

Thomas C.G. Bosch, Mark Wigley, Beatriz Colomina, Brendan Bohannan, Forrest Meggers, Katherine R. Amato Meghan B. Azad , Martin J. Blaser, Kate Brown, Maria Gloria Dominguez-Bello, Stanislav Dusko Ehrlich, Eran Elinav, B. Brett Finlay, Kate Geddie, Naama Geva-Zatorsky, Tamara Giles-Vernick, Philippe Gros, Karen Guillemin, Louis-Patrick Haraoui, Elizabeth Johnson, Frédéric Keck, Jamie Lorimer, Margaret J. McFall-Ngai, Mark Nichter, Sven Petterson, Hendrik Poinar, Tobias Rees, Carolina Tropini, Eduardo A. Undurraga, Liping Zhao, Melissa K. Melby (2024): The potential importance of the built-environment microbiome and its impact on human health. Proceedings of the National Academy of Sciences (PNAS)
First published: 25. April 2024 DOI: 10.1073/pnas.2313971121

Our research field and previous discoveries

Molecularization of Hydra

Novel computational tools and genomic resources have brought a molecular perspective on the Hydra stem cell system. A major breakthrough in research on cnidarian development came with the generation of stably transgenic Hydra by

Tumours have deep roots in evolution

Stem cells emerged in evolution at the point of transition to stable multicellularity. This increase in hierarchical complexity requires robust mechanisms to maintain tissue homeostasis and organism integrity, and to stably interact with the