ABSTRACT
The establishment of host–bacterial colonization during development is a fundamental process influencing the fitness of many organisms, but the factors controlling community membership and influencing the establishment of the microbial ecosystem during development are poorly understood. The freshwater polyp Hydra vulgaris is an excellent model for studying how symbioses operate. Our prior work has shown that the epithelial surface is densely colonized by a stable multi-species bacterial community. Each Hydra species supports long-term associations with a different set of bacteria. In the Hydra viridissima species, 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. In this chapter, we show that studying symbiotic inter-species interactions in Hydra may be a paradigmatic example of a complex symbiotic community that influences the host's health and development.
