title: RpoS regulation of gene expression during exponential growth of Escherichia coli K12.
abstract: RpoS is a major regulator of genes required for adaptation to stationary phase in E. coli. However, the exponential phase expression of some genes is affected by rpoS mutation, suggesting RpoS may also have an important physiological role in growing cells. To test this hypothesis, we examined the regulatory role of RpoS in exponential phase using both genomic and biochemical approaches. Microarray expression data revealed that, in the rpoS mutant, the expression of 268 genes was attenuated while the expression of 24 genes was enhanced. Genes responsible for carbon source transport (the mal operon for maltose), protein folding (dnaK and mopAB), and iron acquisition (fepBD, entCBA, fecI, and exbBD) were positively controlled by RpoS. The importance of RpoS-mediated control of iron acquisition was confirmed by cellular metal analysis which revealed that the intracellular iron content of wild type cells was two-fold higher than in rpoS mutant cells. Surprisingly, many previously identified RpoS stationary-phase dependent genes were not controlled by RpoS in exponential phase and several genes were RpoS-regulated only in exponential phase, suggesting the involvement of other regulators. The expression of RpoS-dependent genes osmY, tnaA and malK was controlled by Crl, a transcriptional regulator that modulates RpoS activity. In summary, the identification of a group of exponential phase genes controlled by RpoS reveals a novel aspect of RpoS function.
authors.affiliation: Department of Biology, McMaster University, Life Sciences Building, Rm. 433, 1280 Main Street West, Hamilton, ON, Canada, L8S 4K1. dongt2@mcmaster.ca
authors.forename: Tao
authors.initials: T
authors.lastname: Dong
authors.forename: Mark G
authors.initials: MG
authors.lastname: Kirchhof
authors.forename: Herb E
authors.initials: HE
authors.lastname: Schellhorn
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D048168:Escherichia coli K12 / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D018507:Gene Expression Regulation, Developmental; D005798:Genes, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D008320:Maltose / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D017510:Protein Folding; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D006360:Heat-Shock Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; C077481:Crl protein, Bacteria; D008320:Maltose; D007501:Iron