title: Role of DNA supercoiling and rpoS sigma factor in the osmotic and growth phase-dependent induction of the gene osmE of Escherichia coli K12.
abstract: Transcription of the gene osmE of Escherichia coli is osmotically inducible and regulated by the growth phase. In a medium of low osmotic pressure, expression of osmE is induced at the onset of stationary phase. At elevated osmotic pressure, a biphasic induction pattern is observed. The first step occurs during exponential phase, and this is followed by a strong induction at the onset of stationary phase. Both steps appear to result from stimulation of transcription at the same promoter, osmEp. In the absence of sigma s, the stationary phase sigma factor encoded by rpoS, osmEp stationary phase induction is abolished, while the osmotic effect is still observed. Mutations that compensate for the absence of sigma s mapped to the gene topA. The effect of such mutation and of novobiocin, an inhibitor of DNA gyrase, suggest that changes in DNA supercoiling are involved in the osmotic induction of osmEp. In addition, modulation of the supercoiling level of a reporter plasmid was observed during growth in rich media. The kinetics of osmEp transcription are discussed in light of the variations of DNA supercoiling.
authors.affiliation: Laboratoire de Microbiologie et Génétique Moléculaire, UPR 9007 du CNRS, Toulouse, France.
authors.forename: A
authors.initials: A
authors.lastname: Conter
authors.forename: C
authors.initials: C
authors.lastname: Menchon
authors.forename: C
authors.initials: C
authors.lastname: Gutierrez
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D004278:DNA, Superhelical / Q000737:chemistry* / Q000378:metabolism; D004587:Electrophoresis, Agar Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter / Q000235:genetics; D008565:Membrane Proteins; D009154:Mutation / Q000235:genetics; D009675:Novobiocin / Q000494:pharmacology; D009690:Nucleic Acid Conformation; D009997:Osmotic Pressure; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012329:RNA, Bacterial / Q000032:analysis / Q000235:genetics; D012808:Sigma Factor / Q000378:metabolism*; D015719:Single-Strand Specific DNA and RNA Endonucleases / Q000378:metabolism; D059005:Topoisomerase II Inhibitors; D014158:Transcription, Genetic / Q000235:genetics; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004278:DNA, Superhelical; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C095975:OsmE protein, E coli; D012329:RNA, Bacterial; D012808:Sigma Factor; D059005:Topoisomerase II Inhibitors; C069567:sigma factor KatF protein, Bacteria; D009675:Novobiocin; D015719:Single-Strand Specific DNA and RNA Endonucleases; D001616:beta-Galactosidase