title: RpoS impacts the lag phase of Salmonella enterica during osmotic stress.
abstract: Salmonella enterica can survive harsh environmental conditions, including hyperosmotic stress. It is well established that the alternative sigma factor, σ(s) (RpoS), is required for maximal survival of enteric pathogens, including S. enterica. Although RpoS levels are greatest during stationary phase or stress conditions, RpoS can be found in S. enterica during growth. However, its activity during growth is poorly characterized. In this study, the impact of RpoS levels on the growth of S. enterica in LB supplemented with 6% NaCl (LB-NaCl) was examined. Cells in stationary phase prior to inoculation into LB-NaCl had a shorter lag phase than did exponential-phase cells. In addition, the deletion of rpoS from S. enterica Typhimurium M-09 (M-09 ΔrpoS) increased the length of lag phase in LB-NaCl relative to the parental strain. Complementation of M-09 ΔrpoS in trans by an inducible plasmid encoding rpoS reduced the length of lag phase. The length of lag phase in both the rpoS mutant and complemented strain was independent of their growth phase prior to inoculation of LB-NaCl. The results from this study demonstrate that the level of RpoS influences the length of lag phase and the growth of S. enterica in hyperosmotic growth conditions.
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Megan
authors.initials: M
authors.lastname: Shiroda
authors.forename: Zach L
authors.initials: ZL
authors.lastname: Pratt
authors.forename: Dorte
authors.initials: D
authors.lastname: Döpfer
authors.forename: Amy C L
authors.initials: AC
authors.lastname: Wong
authors.forename: Charles W
authors.initials: CW
authors.lastname: Kaspar
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D019779:Salmonella enterica / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development*; D017422:Sequence Analysis, DNA; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D012965:Sodium Chloride / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D004269:DNA, Bacterial; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D012965:Sodium Chloride
keywords: RpoS; Salmonella; desiccation; lag phase; osmotic stress; stress response