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Reverse gyrase is not a prerequisite for hyperthermophilic life
Haruyuki Atomi1, Rie Matsumi, Tadayuki Imanaka
1Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Journal of Bacteriology
|July 3, 2004
Summary
Reverse gyrase, essential for DNA supercoiling in hyperthermophilic archaea, was disrupted in Thermococcus kodakaraensis. Its absence hindered growth but did not prove lethal at 90°C, challenging prior assumptions.
Area of Science:
- Molecular Biology
- Genetics
- Extremophile Research
Background:
- Hyperthermophilic archaea thrive at extreme temperatures, requiring specialized molecular mechanisms for DNA maintenance.
- Reverse gyrase is an enzyme believed to be crucial for maintaining DNA structure and stability in high-temperature environments by introducing positive supercoils.
Purpose of the Study:
- To investigate the essentiality of reverse gyrase for the survival and growth of the hyperthermophilic archaeon Thermococcus kodakaraensis.
- To determine if positive supercoiling activity, mediated by reverse gyrase, is a prerequisite for hyperthermophilic life.
Main Methods:
- Gene disruption of the reverse gyrase in Thermococcus kodakaraensis KOD1.
- Phenotypic analysis of the disruptant strain, focusing on growth rates at various temperatures.
- Assay for positive supercoiling activity in both wild-type and disruptant strains.
Main Results:
- The disruptant strain lacking reverse gyrase exhibited a significant retardation in growth, particularly at elevated temperatures.
- Positive supercoiling activity observed in the host strain was absent in the reverse gyrase disruptant.
- Despite growth impairment, the disruptant strain did not display a lethal phenotype at 90°C.
Conclusions:
- Reverse gyrase is not strictly essential for the viability of Thermococcus kodakaraensis at hyperthermophilic temperatures (up to 90°C).
- While important for optimal growth, the enzyme's absence does not preclude survival in extreme heat.
- This study provides experimental evidence that challenges the long-held notion of reverse gyrase as an absolute requirement for hyperthermophilic life.