title: Intracellular growth of Legionella pneumophila in Dictyostelium discoideum, a system for genetic analysis of host-pathogen interactions.
abstract: Conditions were established in which Legionella pneumophila, an intracellular bacterial pathogen, could replicate within the unicellular organism Dictyostelium discoideum. By several criteria, L. pneumophila grew by the same mechanism within D. discoideum as it does in amoebae and macrophages. Bacteria grew within membrane-bound vesicles associated with rough endoplasmic reticulum, and L. pneumophila dot/icm mutants, blocked for growth in macrophages and amoebae, also did not grow in D. discoideum. Internalized L. pneumophila avoided degradation by D. discoideum and showed evidence of reduced fusion with endocytic compartments. The ability of L. pneumophila to grow within D. discoideum depended on the growth state of the cells. D. discoideum grown as adherent monolayers was susceptible to L. pneumophila infection and to contact-dependent cytotoxicity during high-multiplicity infections, whereas D. discoideum grown in suspension was relatively resistant to cytotoxicity and did not support intracellular growth. Some known D. discoideum mutants were examined for their effect on growth of L. pneumophila. The coronin mutant and the myoA/B double myosin I mutant were more permissive than wild-type strains for intracellular growth. Growth of L. pneumophila in a G(beta) mutant was slightly reduced compared to the parent strain. This work demonstrates the usefulness of the L. pneumophila-D. discoideum system for genetic analysis of host-pathogen interactions.
authors.affiliation: Howard Hughes Medical Institute, Department of Molecular Biology and Microbiology, Tufts University Medical School, Boston, Massachusetts 02111, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Solomon
authors.forename: A
authors.initials: A
authors.lastname: Rupper
authors.forename: J A
authors.initials: JA
authors.lastname: Cardelli
authors.forename: R R
authors.initials: RR
authors.lastname: Isberg
mesh_terms: D000818:Animals; D003470:Culture Media; D004023:Dictyostelium / Q000235:genetics / Q000382:microbiology*; D005798:Genes, Bacterial; D007424:Intracellular Fluid / Q000382:microbiology; D007425:Intracellular Membranes; D016952:Legionella pneumophila / Q000235:genetics / Q000254:growth & development*; D008247:Lysosomes; D008565:Membrane Proteins
chemical_list: D003470:Culture Media; D008565:Membrane Proteins