title: Bacteria-bacteria interactions within the microbiota of the ancestral metazoan Hydra contribute to fungal resistance.
abstract: Epithelial surfaces of most animals are colonized by diverse microbial communities. Although it is generally agreed that commensal bacteria can serve beneficial functions, the processes involved are poorly understood. Here we report that in the basal metazoan Hydra, ectodermal epithelial cells are covered with a multilayered glycocalyx that provides a habitat for a distinctive microbial community. Removing this epithelial microbiota results in lethal infection by the filamentous fungus Fusarium sp. Restoring the complex microbiota in gnotobiotic polyps prevents pathogen infection. Although mono-associations with distinct members of the microbiota fail to provide full protection, additive and synergistic interactions of commensal bacteria are contributing to full fungal resistance. Our results highlight the importance of resident microbiota diversity as a protective factor against pathogen infections. Besides revealing insights into the in vivo function of commensal microbes in Hydra, our findings indicate that interactions among commensal bacteria are essential to inhibit pathogen infection.
authors.affiliation: Zoological Institute, Christian-Albrechts University Kiel, Kiel, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Fraune
authors.affiliation: Zoological Institute, Christian-Albrechts University Kiel, Kiel, Germany.
authors.forename: Friederike
authors.initials: F
authors.lastname: Anton-Erxleben
authors.affiliation: Zoological Institute, Christian-Albrechts University Kiel, Kiel, Germany.
authors.forename: René
authors.initials: R
authors.lastname: Augustin
authors.affiliation: Zoological Institute, Christian-Albrechts University Kiel, Kiel, Germany.
authors.forename: Sören
authors.initials: S
authors.lastname: Franzenburg
authors.affiliation: Zoological Institute, Christian-Albrechts University Kiel, Kiel, Germany.
authors.forename: Mirjam
authors.initials: M
authors.lastname: Knop
authors.affiliation: Zoological Institute, Christian-Albrechts University Kiel, Kiel, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Schröder
authors.affiliation: Zoological Institute, Christian-Albrechts University Kiel, Kiel, Germany.
authors.forename: Doris
authors.initials: D
authors.lastname: Willoweit-Ohl
authors.affiliation: Zoological Institute, Christian-Albrechts University Kiel, Kiel, Germany.
authors.forename: Thomas C G
authors.initials: TC
authors.lastname: Bosch
mesh_terms: D000818:Animals; D001419:Bacteria / Q000145:classification*; D004847:Epithelial Cells; D005658:Fungi / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006829:Hydra / Q000382:microbiology*; D013559:Symbiosis