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Decrease in cell viability due to the accumulation of spermidine in spermidine acetyltransferase-deficient mutant of
J Fukuchi1, K Kashiwagi, M Yamagishi
1Faculty of Pharmaceutical Sciences, Chiba University, Japan.
The Journal of Biological Chemistry
|August 11, 1995
Summary
In Escherichia coli, excess spermidine accumulation during the stationary phase impairs cell viability by inhibiting protein synthesis, particularly ribosome modulation factor. This highlights spermidine acetyltransferase's (speG) crucial role in maintaining cell health.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Spermidine is a polyamine involved in various cellular processes.
- The role of spermidine acetyltransferase (speG) in Escherichia coli physiology remains incompletely understood.
- Cellular accumulation of spermidine can impact growth and viability.
Purpose of the Study:
- To investigate the physiological functions of spermidine acetyltransferase (speG) in Escherichia coli.
- To determine the effects of spermidine accumulation on cell growth, viability, and macromolecular synthesis.
- To elucidate the molecular mechanisms underlying spermidine-induced toxicity in E. coli.
Main Methods:
- Utilized a speG gene-deficient mutant (CAG2242) and a cloned speG gene for complementation studies.
- Assessed bacterial growth and cell viability under varying spermidine concentrations.
- Analyzed DNA, RNA, and protein synthesis rates at different growth phases.
- Investigated the impact of spermidine on specific protein levels, including ribosome modulation factor and OmpC protein.
Main Results:
- E. coli CAG2242 showed normal growth but decreased viability at 48 hours with 0.5 mM spermidine addition.
- Spermidine accumulation was approximately 3-fold higher in the mutant with added spermidine.
- Complementation with the cloned speG gene restored cell viability.
- Spermidine accumulation at the late stationary phase inhibited protein synthesis, but not DNA or RNA synthesis.
- Levels of ribosome modulation factor and OmpC protein were significantly reduced, with translational regulation implicated.
Conclusions:
- Accumulated spermidine exerts toxicity during the late stationary phase of E. coli growth.
- Inhibition of protein synthesis, particularly ribosome modulation factor, is a key factor contributing to spermidine-induced cell death.
- The speG gene product plays a vital role in mitigating spermidine toxicity and maintaining cell viability in E. coli.