The individual as metaorganism
Multicellular organisms exist as metaorganisms comprised of the macroscopic host and synergistic interdependence 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 (e.g.skin, 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.
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.
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