sigmaS, a major player in the response to environmental stresses in Escherichia coli: role, regulation and mechanisms of promoter recognition

Abstract

Bacterial cells often face hostile environmental conditions, to which they adapt by activation of stress responses. In Escherichia coli, environmental stresses resulting in significant reduction in growth rate stimulate the expression of the rpoS gene, encoding the alternative σ factor σ(S). The σ(S) protein associates with RNA polymerase, and through transcription of genes belonging to the rpoS regulon allows the activation of a 'general stress response', which protects the bacterial cell from harmful environmental conditions. Each step of this process is finely tuned in order to cater to the needs of the bacterial cell: in particular, selective promoter recognition by σ(S) is achieved through small deviations from a common consensus DNA sequence for both σ(S) and the housekeeping σ(70). Recognition of specific DNA elements by σ(S) is integrated with the effects of environmental signals and the interaction with regulatory proteins, in what represents a fascinating example of multifactorial regulation of gene expression. In this report, we discuss the function of the rpoS gene in the general stress response, and review the current knowledge on regulation of rpoS expression and on promoter recognition by σ(S).

Repression of Flagellar Genes in Exponential Phase by CsgD and CpxR, Two Crucial Modulators of Escherichia coli Biofilm Formation

“…In addition, CsgD makes other connections with global regulators, thus diminishing the expression of FliA by alternative routes. For example, CsgD represses the transcription of DksA which, together with ppGpp, plays an important role in reorganizing gene expression in stationary phase, in particular by inducing the RpoS regulon (58). We also found that CsgD activates the transcription of ihfB (Fig.…”

The General Stress Response σS Is Regulated by a Partner Switch in the Gram-negative Bacterium Shewanella oneidensis

“…Among them, the general stress response (GSR) 3 has been deeply studied in Escherichia coli (1)(2)(3). When E. coli is submitted to stressful life conditions including nutrient starvation in stationary phase, osmolarity variations, or pH modifications, the alternative transcriptional sigma factor of the GSR, S (also called RpoS), allows a reorganization of gene expression by controlling the S regulon that contains more than 500 genes.…”

Engineering Synthetic Multistress Tolerance in Escherichia coli by Using a Deinococcal Response Regulator, DR1558

“…10), and heat (Table 2) stresses, S -dependent genes provide cross-protection against several different stresses. This cross-protection in E. coli occurs as a result of rpoS induction and S accumulation upon challenge with a specific environmental stress (40,74). Collectively, the results indicate that the multistress tolerance phenotype conferred by DR1558 is likely to be routed through RpoS in Ec-1558 cells.…”

“…This result emphasizes the fact that S levels are critically regulated in the cell, and a simple strategy, such as overexpression of the rpoS gene, cannot confer stress resistance. rpoS regulation in E. coli is highly complex and is modulated through different proteins, adaptors, and noncoding RNAs that affect the transcription, translation, and posttranslational stability of this gene (40,74). In these two studies (77,78), S accumulation was facilitated through the increased posttranslational stability of this protein in the cell.…”

“…Fifty micrograms of cell-free lysates from each strain was resolved on nondenaturing gels, and bands were stained for the detection of catalase activity. The activity band (#) was identified as KatE by nLC-MS-MS. tal conditions (40). To further examine this mechanism, Ec-1558 cells were exposed to different stress conditions, including a low pH, a high temperature, and high NaCl concentrations, and the survival of these cells was compared with that of Ec-pR cells.…”