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Inorganic polyphosphate and the induction of rpoS expression
1Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060, Japan. shiba@moby.hokudai.ac.jp
Summary
Inorganic polyphosphate (poly(P)) is crucial for Escherichia coli
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Inorganic polyphosphate (poly(P)) is a polymer of phosphate residues.
- Poly(P) plays diverse roles in bacterial physiology, including stress resistance.
- The regulation of poly(P) metabolism and its specific functions are not fully understood.
Purpose of the Study:
- To investigate the role of poly(P) in hydrogen peroxide (H2O2) resistance in Escherichia coli.
- To elucidate the relationship between poly(P) metabolism and the expression of stress-related genes, particularly catalases and the rpoS sigma factor.
Main Methods:
- Genetic manipulation of poly(P) levels in E. coli using a yeast exopolyphosphatase.
- Assessing H2O2 resistance in engineered strains.
- Analyzing the expression of katE and rpoS genes under different conditions.
- Complementation experiments using ppk gene.
Main Results:
- Overexpression of yeast exopolyphosphatase significantly reduced intracellular poly(P) levels and H2O2 resistance.
- The reduction in H2O2 resistance was more pronounced in katG mutants, highlighting the role of KatE (HPII).
- Poly(P) depletion inhibited the induction of katE and rpoS expression.
- Restoration of poly(P) levels via ppk expression rescued H2O2 resistance and gene expression.
Conclusions:
- Poly(P) is essential for full H2O2 resistance in E. coli, particularly through the stationary-phase catalase KatE.
- Poly(P) plays a regulatory role in the induction of rpoS expression, independent of stringent response nucleotides.
- These findings reveal a novel mechanism linking poly(P) metabolism to bacterial stress response regulation.