From protists to humans, all animals and plants are inhabited by microbial organisms. There is an increasing appreciation that these resident microbes influence fitness of their plant and animal hosts, ultimately forming a metaorganism consisting of a uni- or multicellular host and a community of associated microorganisms. Research on host-microbe interactions has become an emerging cross-disciplinary field. In both vertebrates as well as invertebrates a complex microbiome confers immunological, metabolic and behavioural benefits; its disturbance can contribute to the development of disease states. However, the molecular and cellular mechanisms controlling interactions within the metaorganisms are poorly understood and many key interactions between the associated organisms remain unknown. The CRC 1182 at Kiel University adresses theses questions particularly by investigating: ·          the specific functional consequences of the interactions, ·          the underlying regulatory principles, ·          the resulting impact on host life history and evolutionary fitness in selected host systems. ( https://www.metaorganism-research.com/ )