The alternative sigma factor, sigmaS, affects polyhydroxyalkanoate metabolism in Pseudomonas putida
Laura J Raiger-Iustman1, Jimena A Ruiz
1Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
FEMS Microbiology Letters
|May 24, 2008
Summary
The sigma(S) factor influences polyhydroxyalkanoate (PHA) metabolism in Pseudomonas putida. A mutant lacking sigma(S) showed altered PHA accumulation and degradation, with PHA enhancing stress tolerance.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Polyhydroxyalkanoates (PHAs) are biopolyesters with diverse applications.
- The stationary sigma factor, sigma(S), plays a crucial role in bacterial stress response and adaptation.
- Understanding the regulation of PHA metabolism is essential for optimizing its production and utilization.
Purpose of the Study:
- To investigate the role of the sigma(S) factor in regulating polyhydroxyalkanoate (PHA) metabolism in Pseudomonas putida KT2440.
- To assess the impact of sigma(S) on PHA accumulation, degradation, and the expression of PHA synthesis and depolymerase genes.
- To evaluate the effect of PHA accumulation on the survival and stress tolerance of Pseudomonas putida under conditions lacking sigma(S).
Main Methods:
- Construction and characterization of an rpoS-negative mutant of Pseudomonas putida KT2440.
- Measurement of PHA accumulation and degradation rates in wild-type and mutant strains.
- Analysis of the expression of phaC1 and phaZ genes using translational fusions.
- Assessment of bacterial survival and oxidative stress tolerance under varying PHA accumulation conditions.
Main Results:
- The rpoS mutant exhibited a higher PHA degradation rate compared to the wild-type strain.
- Expression of PHA synthesis (phaC1) and depolymerase (phaZ) genes was increased in the rpoS mutant during the stationary phase.
- Accumulated PHA significantly enhanced the survival and oxidative stress tolerance of the rpoS mutant.
- These findings suggest an indirect regulatory role for sigma(S) in PHA metabolism.
Conclusions:
- Sigma(S) influences polyhydroxyalkanoate metabolism in Pseudomonas putida, likely through indirect regulation of PHA synthesis and degradation genes.
- Polyhydroxyalkanoate accumulation serves as a protective mechanism, enhancing cellular fitness and stress tolerance in Pseudomonas putida strains lacking sigma(S), particularly under stationary phase conditions.
- The study highlights the interplay between sigma(S)-mediated stress responses and carbon/energy storage pathways like PHA metabolism.
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