title: Hfq and ArcA are involved in the stationary phase-dependent activation of Salmonella pathogenicity island 1 (SPI1) under shaking culture conditions.
abstract: In Salmonella enterica serovar Typhimurium, many genes encoded within Salmonella pathogenicity island 1 (SPI1) are required to induce intestinal/diarrheal disease. In this study, we compared the expression of four SPI1 genes (hilA, invF, prgH, and sipC) under shaking and standing culture conditions and found that the expression of these genes was highest during the transition from the exponential to stationary phase under shaking conditions. To identify regulators associated with the stationary phase-dependent activation of SPI1, the effects of selected regulatory genes, including relA/spoT (ppGpp), luxS, ihfB, hfq, and arcA, on the expression of hilA and invF were compared under shaking conditions. Mutations in the hfq and arcA genes caused a reduction in hilA and invF expression (more than 2-fold) in the early stationary phase only, whereas the lack of ppGpp and IHF decreased hilA and invF gene expression during the entire stationary phase. We also found that hfq and arcA mutations caused a reduction of hilD expression upon entry into the stationary phase under shaking culture conditions. Taken together, these results suggest that Hfq and ArcA regulate the hilD promoter, causing an accumulation of HilD, which can trigger a stationary phase-dependent activation of SPI1 genes under shaking culture conditions.
authors.affiliation: Department of Agricultural Biotechnology, Center for Agricultural Biomaterials, and Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea.
authors.forename: Sangyong
authors.initials: S
authors.lastname: Lim
authors.forename: Hyunjin
authors.initials: H
authors.lastname: Yoon
authors.forename: Minjeong
authors.initials: M
authors.lastname: Kim
authors.forename: Ahreum
authors.initials: A
authors.lastname: Han
authors.forename: Jihae
authors.initials: J
authors.lastname: Choi
authors.forename: Jeongjoon
authors.initials: J
authors.lastname: Choi
authors.forename: Sangryeol
authors.initials: S
authors.lastname: Ryu
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D044404:Genomic Islands; D035001:Host Factor 1 Protein / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C119660:HilD protein, Salmonella typhimurium; D035001:Host Factor 1 Protein; D012097:Repressor Proteins; D014157:Transcription Factors