title: Salmonella typhimurium is pathogenic for Dictyostelium cells and subverts the starvation response.
abstract: In unicellular amoebae, such as Dictyostelium discoideum, bacterial phagocytosis is a food hunting device, while in higher organisms it is the first defence barrier against microbial infection. In both cases, pathogenic bacteria exploit phagocytosis to enter the cell and multiply intracellularly. Salmonella typhimurium, the agent of food-borne gastroenteritis, is phagocytosed by both macrophages and Dictyostelium cells. By using cell biological assays and global transcriptional analysis with DNA microarrays covering the Dictyostelium genome, we show here that S. typhimurium is pathogenic for Dictyostelium cells. Depending on the degree of virulence, which in turn depended on bacterial growth conditions, Salmonella could kill Dictyostelium cells or inhibit their growth and development. In the early phase of infection in non-nutrient buffer, the ingested bacteria escaped degradation, induced a starvation-like transcriptional response but inhibited selectively genes required for chemotaxis and aggregation. This way differentiation of the host cells into spore and stalk cells was blocked or delayed, which in turn is likely to be favourable for the establishment of a replicative niche for Salmonella. Inhibition of the aggregation competence and chemotactic streaming of aggregation-competent cells in the presence of Salmonella suggests interference with cAMP signalling.
authors.affiliation: Department of Clinical and Biological Sciences, University of Turin, AOU S. Luigi, 10043 Orbassano (Torino), Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Sillo
authors.forename: Jan
authors.initials: J
authors.lastname: Matthias
authors.forename: Roman
authors.initials: R
authors.lastname: Konertz
authors.forename: Salvatore
authors.initials: S
authors.lastname: Bozzaro
authors.forename: Ludwig
authors.initials: L
authors.lastname: Eichinger
mesh_terms: D002470:Cell Survival; D000242:Cyclic AMP / Q000378:metabolism; D004023:Dictyostelium / Q000254:growth & development / Q000382:microbiology* / Q000502:physiology*; D020869:Gene Expression Profiling; D046228:Microarray Analysis; D010587:Phagocytosis; D012486:Salmonella typhimurium / Q000254:growth & development / Q000472:pathogenicity*; D015398:Signal Transduction
chemical_list: D000242:Cyclic AMP