The DNA binding protein from starved cells (Dps) is a general stress protein that provides Escherichia coli protection from osmotic, oxidative, and acid stresses. While Dps production and accumulation is primarily associated with stationary phase, during log phase, this protein protects against oxidative stress in an OxyR-dependent manner. In this study, evidence is provided that expands the role of Dps in acid tolerance to both log- and stationary-phase E. coli O157:H7. The transcription of dps occurred in log-phase cells without OxyR or stress and was upregulated during entry into stationary phase. The expression in log and stationary phase involved σ70 and σs, respectively, with both sigma factors recognizing the same promoter region. Site-directed mutagenesis identified an extended - 10 region that was essential to both σ70 and σs transcription of dps. cAMP receptor protein (CRP) was found to repress dps expression as a crp mutant had a significant increase in the dps mRNA level. However, a CRP binding site was not found in the dps promoter and upregulation of dps in the crp mutant was absent in a crp rpoS double mutant. The findings from this study demonstrated that dps was expressed at a basal level during growth, both σ70- and σs-driven transcription required an extended - 10, and CRP repression is mediated through the alternative sigma factor σs (rpoS).
|Original language||English (US)|
|Number of pages||9|
|Journal||Biochimica et Biophysica Acta - Gene Structure and Expression|
|State||Published - Jan 2006|
Bibliographical noteFunding Information:
We thank Richard Burgess for antibody to σ s and Sang-Ho Choi for his assistance in the construction of the crp and rpoS mutants. The valuable discussions and critical review of the manuscript by Kia Foong Hung, Jeffery Byrd, and Stephen Barclay are greatly appreciated. This work was supported by HATCH grant WIS04530.
- - 10 region
- Acid tolerance
- E. coli O157:H7
- dps regulation