title: What hydra has to say about the role and origin of symbiotic interactions.
abstract: The Hydra holobiont involves at least three types of organisms that all share a long coevolutionary history and appear to depend on each other. Here I review how symbiotic algae and stably associated bacteria interact with the Hydra host and where in the tissue they are located. In particular I discuss the role of Toll-like receptor (TLR) signaling in maintaining Hydra's species-specific microbiota. I also discuss studies in Hydra viridis and its symbiotic Chlorella algae which indicate that the symbiotic algae are critically involved in the control of sexual differentiation in green Hydra. Finally, I review the state of "omics" in this tripartite association and the fact that the functioning of this holobiont is also a tale of several genomes.
authors.affiliation: Zoologisches Institut der Christian-Albrechts-Universität zu Kiel, Germany. tbosch@zoologie.uni-kiel.de
authors.forename: Thomas C G
authors.initials: TC
authors.lastname: Bosch
mesh_terms: D000818:Animals; D001419:Bacteria / Q000254:growth & development; D018407:Bacterial Physiological Phenomena; D002708:Chlorella / Q000254:growth & development / Q000502:physiology*; D023281:Genomics / Q000379:methods; D006829:Hydra / Q000382:microbiology* / Q000502:physiology*; D055432:Metabolomics / Q000379:methods; D040901:Proteomics / Q000379:methods; D013559:Symbiosis; D051193:Toll-Like Receptors / Q000378:metabolism
chemical_list: D051193:Toll-Like Receptors