title: Controlled induction of the RpoS regulon in Escherichia coli, using an RpoS-expressing plasmid.
abstract: RpoS, an alternative sigma factor produced by many gram-negative bacteria, primarily controls genes that are expressed in stationary phase in response to nutrient deprivation. To test the idea that induction of RpoS in the exponential phase, when RpoS is not normally expressed, increases RpoS-dependent gene expression, we constructed a plasmid carrying the rpoS gene under the control of an IPTG (isopropyl-beta-D-thiogalactopyranoside)-inducible T7lac promoter. Northern and Western analyses revealed that levels of RpoS mRNA and protein, respectively, increased in response to the inducer IPTG. Assays of changes in RpoS-dependent functions (catalase activity and glycogen accumulation), confirmed that induced RpoS was functional in exponential phase and was sufficient for the expression of RpoS-dependent functions. Controlled expression of RpoS and RpoS-dependent genes by plasmid-encoded rpoS may thus offer a useful tool for the study of RpoS-dependent gene expression.
authors.affiliation: Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada.
authors.forename: Guozhu
authors.initials: G
authors.lastname: Chen
authors.forename: Herb E
authors.initials: HE
authors.lastname: Schellhorn
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D015152:Blotting, Northern; D015153:Blotting, Western; D002374:Catalase / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006003:Glycogen / Q000096:biosynthesis; D010957:Plasmids; D012333:RNA, Messenger / Q000032:analysis; D018085:Regulon / Q000235:genetics / Q000502:physiology; D012808:Sigma Factor / Q000032:analysis / Q000235:genetics* / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D012333:RNA, Messenger; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D006003:Glycogen; D002374:Catalase