title: ppGpp-dependent stationary phase induction of genes on Salmonella pathogenicity island 1.
abstract: We have examined expression of the genes on Salmonella pathogenicity island 1 (SPI1) during growth under the physiologically well defined standard growth condition of Luria-Bertani medium with aeration. We found that the central regulator hilA and the genes under its control are expressed at the onset of stationary phase. Interestingly, the two-component regulatory genes hilC/hilD, sirA/barA, and ompR, which are known to modulate expression from the hilA promoter (hilAp) under so-called "inducing conditions" (Luria-Bertani medium containing 0.3 m NaCl without aeration), acted under standard conditions at the stationary phase induction level. The induction of hilAp depended not on RpoS, the stationary phase sigma factor, but on the stringent signal molecule ppGpp. In the ppGpp null mutant background, hilAp showed absolutely no activity. The stationary phase induction of hilAp required spoT but not relA. Consistent with this requirement, hilAp was also induced by carbon source deprivation, which is known to transiently elevate ppGpp mediated by spoT function. The observation that amino acid starvation elicited by the addition of serine hydroxamate did not induce hilAp in a RelA(+) SpoT(+) strain suggested that, in addition to ppGpp, some other alteration accompanying entry into the stationary phase might be necessary for induction. It is speculated that during the course of infection Salmonella encounters various stressful environments that are sensed and translated to the intracellular signal, ppGpp, which allows expression of Salmonella virulence genes, including SPI1 genes.
authors.affiliation: Genome Research Center for Enteropathogenic Bacteria and Research Institute of Vibrio Infection, Chonnam National University Medical College, Kwangju 501-746, South Korea.
authors.forename: Miryoung
authors.initials: M
authors.lastname: Song
authors.forename: Hyun-Ju
authors.initials: HJ
authors.lastname: Kim
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Kim
authors.forename: Minsang
authors.initials: M
authors.lastname: Shin
authors.forename: Hyun Chul
authors.initials: HC
authors.lastname: Lee
authors.forename: Yeongjin
authors.initials: Y
authors.lastname: Hong
authors.forename: Joon Haeng
authors.initials: JH
authors.lastname: Rhee
authors.forename: Hyunjin
authors.initials: H
authors.lastname: Yoon
authors.forename: Sangryeol
authors.initials: S
authors.lastname: Ryu
authors.forename: Sangyong
authors.initials: S
authors.lastname: Lim
authors.forename: Hyon E
authors.initials: HE
authors.lastname: Choy
mesh_terms: D001426:Bacterial Proteins; D002455:Cell Division; D002460:Cell Line; D003470:Culture Media; D004591:Electrophoresis, Polyacrylamide Gel; D015964:Gene Expression Regulation, Bacterial; D044404:Genomic Islands; D006159:Guanosine Tetraphosphate / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012475:Salmonella / Q000378:metabolism*; D012480:Salmonella Infections / Q000378:metabolism*; D012965:Sodium Chloride / Q000737:chemistry; D013997:Time Factors; D015534:Trans-Activators / Q000235:genetics*; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; C102236:HilA protein, Salmonella; D015534:Trans-Activators; D006159:Guanosine Tetraphosphate; D012965:Sodium Chloride; D001616:beta-Galactosidase