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The H‐NS‐like protein StpA represses the RpoS (σ 38 ) regulon during exponential growth of Salmonella Typhimurium
Author(s) -
Lucchini Sacha,
McDermott Paul,
Thompson Arthur,
Hinton Jay C.D.
Publication year - 2009
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2009.06929.x
Subject(s) - rpos , regulon , sigma factor , biology , sigma , gene , regulator , response regulator , salmonella , escherichia coli , genetics , gene expression , promoter , bacteria , rna polymerase , bacterial protein , physics , quantum mechanics
Summary StpA is a paralogue of the nucleoid‐associated protein H‐NS that is conserved in a range of enteric bacteria and had no known function in Salmonella Typhimurium. We show that 5% of the Salmonella genome is regulated by StpA, which contrasts with the situation in Escherichia coli where deletion of stpA only had minor effects on gene expression. The StpA‐dependent genes of S. Typhimurium are a specific subset of the H‐NS regulon that are predominantly under the positive control of σ 38 (RpoS), CRP‐cAMP and PhoP. Regulation by StpA varied with growth phase; StpA controlled σ 38 levels at mid‐exponential phase by preventing inappropriate activation of σ 38 during rapid bacterial growth. In contrast, StpA only activated the CRP‐cAMP regulon during late exponential phase. ChIP‐chip analysis revealed that StpA binds to PhoP‐dependent genes but not to most genes of the CRP‐cAMP and σ 38 regulons. In fact, StpA indirectly regulates σ 38 ‐dependent genes by enhancing σ 38 turnover by repressing the anti‐adaptor protein rssC . We discovered that StpA is essential for the dynamic regulation of σ 38 in response to increased glucose levels. Our findings identify StpA as a novel growth phase‐specific regulator that plays an important physiological role by linking σ 38 levels to nutrient availability.