ABSTRACT
Animals evolved in a world dominated by bacteria and rely on their bacterial partners in many ways. The specific dialogue of a bacterium with its animal host is a fascinating research topic of increasing importance. However, we still lack knowledge about the signals exchanged between the host and its partners, and how they influence the fitness and physiology of each other. The freshwater polyp Hydra is an ideal model metaorganism to study inter-kingdom communication. A main component of the Hydra microbiome is a bacterium of the genus Curvibacter. This bacterium colonizes the ectodermal epithelium and is vertically transmitted during Hydra reproduction. It is involved in protecting the metaorganism Hydra against fungal infection and its abundance depends on the epithelial homeostasis of its host. Interestingly, Hydra is able to specifically modify quorum sensing signals of Curvibacter. In return, Curvibacter induce the expression of small secreted peptides in Hydra that exhibit an antagonistic activity to the Wnt-pathway, an important developmental pathway in Hydra. Additional recent achievements in culturing, sequencing and transformation of Curvibacter cells turn this bacterium into an ideal model symbiont to explore the dialogue of Hydra and its bacteria on a mechanistic level.
