title: DNA topology and adaptation of Salmonella typhimurium to an intracellular environment.
abstract: The expression of genes coding for determinants of DNA topology in the facultative intracellular pathogen Salmonella typhimurium was studied during adaptation by the bacteria to the intracellular environment of J774A.1 macrophage-like cells. A reporter plasmid was used to monitor changes in DNA supercoiling during intracellular growth. Induction of the dps and spv genes, previously shown to be induced in the macrophage, was detected, as was expression of genes coding for DNA gyrase, integration host factor and the nucleoid-associated protein H-NS. The topA gene, coding for the DNA relaxing enzyme topoisomerase I, was not induced. Reporter plasmid data showed that bacterial DNA became relaxed following uptake of S. typhimurium cells by the macrophage. These data indicate that DNA topology in S. typhimurium undergoes significant changes during adaptation to the intracellular environment. A model describing how this process may operate is discussed.
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, University of Dublin, Trinity College, Republic of Ireland.
authors.forename: D G
authors.initials: DG
authors.lastname: Marshall
authors.forename: F
authors.initials: F
authors.lastname: Bowe
authors.forename: C
authors.initials: C
authors.lastname: Hale
authors.forename: G
authors.initials: G
authors.lastname: Dougan
authors.forename: C J
authors.initials: CJ
authors.lastname: Dorman
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D002460:Cell Line; D004264:DNA Topoisomerases, Type I / Q000235:genetics; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins / Q000235:genetics; D005798:Genes, Bacterial; D034982:Integration Host Factors; D007424:Intracellular Fluid / Q000382:microbiology; D012486:Salmonella typhimurium / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C083911:DPS protein, Bacteria; C031908:H-NS protein, bacteria; D034982:Integration Host Factors; C440508:integration host factor, Salmonella; D004264:DNA Topoisomerases, Type I