title: Immune-directed support of rich microbial communities in the gut has ancient roots.
abstract: The animal gut serves as a primary location for the complex host-microbe interplay that is essential for homeostasis and may also reflect the types of ancient selective pressures that spawned the emergence of immunity in metazoans. In this review, we present a phylogenetic survey of gut host-microbe interactions and suggest that host defense systems arose not only to protect tissue directly from pathogenic attack but also to actively support growth of specific communities of mutualists. This functional dichotomy resulted in the evolution of immune systems much more tuned for harmonious existence with microbes than previously thought, existing as dynamic but primarily cooperative entities in the present day. We further present the protochordate Ciona intestinalis as a promising model for studying gut host-bacterial dialogue. The taxonomic position, gut physiology and experimental tractability of Ciona offer unique advantages in dissecting host-microbe interplay and can complement studies in other model systems.
authors.affiliation: Department of Pediatrics, University of South Florida Morsani College of Medicine, USF/ACH Children's Research Institute, 140 7th Avenue South, St. Petersburg, FL 33701, USA. Electronic address: ldishaw@health.usf.edu.
authors.forename: Larry J
authors.initials: LJ
authors.lastname: Dishaw
authors.affiliation: Department of Pediatrics, University of South Florida Morsani College of Medicine, USF/ACH Children's Research Institute, 140 7th Avenue South, St. Petersburg, FL 33701, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Cannon
authors.affiliation: Department of Pediatrics, University of South Florida Morsani College of Medicine, USF/ACH Children's Research Institute, 140 7th Avenue South, St. Petersburg, FL 33701, USA; Department of Molecular Genetics, All Children's Hospital-Johns Hopkins Medicine, 501 6th Avenue South, St. Petersburg, FL 33701, USA.
authors.forename: Gary W
authors.initials: GW
authors.lastname: Litman
authors.affiliation: Department of Surgery, Duke University Medical Center, Box 2605, Durham, NC 27710, USA.
authors.forename: William
authors.initials: W
authors.lastname: Parker
mesh_terms: D000818:Animals; D005075:Biological Evolution; D043344:Chordata / Q000276:immunology / Q000382:microbiology; D002938:Ciona intestinalis / Q000254:growth & development / Q000382:microbiology*; D003063:Cnidaria / Q000276:immunology / Q000382:microbiology; D041981:Gastrointestinal Tract / Q000382:microbiology*; D006801:Humans; D008322:Mammals / Q000382:microbiology; D023421:Models, Animal
keywords: Ciona intestinalis; Gut biofilms; Gut host–microbe interactions; Gut immune effectors; Gut immune evolution; Mutualism