title: Dissection of Francisella-Host Cell Interactions in Dictyostelium discoideum.
abstract: Francisella bacteria cause severe disease in both vertebrates and invertebrates and include one of the most infectious human pathogens. Mammalian cell lines have mainly been used to study the mechanisms by which Francisella manipulates its host to replicate within a large variety of hosts and cell types, including macrophages. Here, we describe the establishment of a genetically and biochemically tractable infection model: the amoeba Dictyostelium discoideum combined with the fish pathogen Francisella noatunensis subsp. noatunensis. Phagocytosed F. noatunensis subsp. noatunensis interacts with the endosomal pathway and escapes further phagosomal maturation by translocating into the host cell cytosol. F. noatunensis subsp. noatunensis lacking IglC, a known virulence determinant required for Francisella intracellular replication, follows the normal phagosomal maturation and does not grow in Dictyostelium. The attenuation of the F. noatunensis subsp. noatunensis ΔiglC mutant was confirmed in a zebrafish embryo model, where growth of F. noatunensis subsp. noatunensis ΔiglC was restricted. In Dictyostelium, F. noatunensis subsp. noatunensis interacts with the autophagic machinery. The intracellular bacteria colocalize with autophagic markers, and when autophagy is impaired (Dictyostelium Δatg1), F. noatunensis subsp. noatunensis accumulates within Dictyostelium cells. Altogether, the Dictyostelium-F. noatunensis subsp. noatunensis infection model recapitulates the course of infection described in other host systems. The genetic and biochemical tractability of the system allows new approaches to elucidate the dynamic interactions between pathogenic Francisella and its host organism.
authors.affiliation: Centre for Integrative Microbial Evolution (CIME), University of Oslo, Oslo, Norway.|Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway.
authors.forename: Elisabeth O
authors.initials: EO
authors.lastname: Lampe
authors.affiliation: Section of Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Brenz
authors.affiliation: Section of Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
authors.forename: Lydia
authors.initials: L
authors.lastname: Herrmann
authors.affiliation: Department of Biosciences, University of Oslo, Oslo, Norway.
authors.forename: Urska
authors.initials: U
authors.lastname: Repnik
authors.affiliation: Department of Biosciences, University of Oslo, Oslo, Norway.
authors.forename: Gareth
authors.initials: G
authors.lastname: Griffiths
authors.affiliation: Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden.
authors.forename: Carl
authors.initials: C
authors.lastname: Zingmark
authors.affiliation: Department of Clinical Microbiology, Clinical Bacteriology, and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Sjöstedt
authors.affiliation: Centre for Integrative Microbial Evolution (CIME), University of Oslo, Oslo, Norway.|Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway.
authors.forename: Hanne C
authors.initials: HC
authors.lastname: Winther-Larsen
authors.affiliation: Section of Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany hagedorn@bnitm.de.
authors.forename: Monica
authors.initials: M
authors.lastname: Hagedorn
mesh_terms: D003600:Cytosol / Q000382:microbiology; D004023:Dictyostelium / Q000382:microbiology*; D011992:Endosomes / Q000382:microbiology; D005603:Francisella / Q000254:growth & development*; D054884:Host-Pathogen Interactions; D008954:Models, Biological; D010587:Phagocytosis