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Mutation frequency decline in a rel strain of E. coli coli B/r
Molecular & General Genetics : MGG
|April 1, 1980
Summary
Mutation frequency decline (MFD) in E. coli does not require stringent control. This study found that relaxed strains exhibit similar MFD kinetics, challenging previous hypotheses about transcription regulation at tRNA genes.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Mutation frequency decline (MFD) is a phenomenon observed in UV-irradiated E. coli.
- MFD involves the loss of potential mutants when bacteria are incubated under suboptimal protein synthesis conditions before plating.
- A prevailing hypothesis linked MFD to stringent control of transcription at tRNA genes influencing DNA repair.
Purpose of the Study:
- To investigate the role of stringent control in the MFD mechanism.
- To determine if the relaxed (rel) phenotype affects MFD kinetics in E. coli.
Main Methods:
- Construction of a rel mutant (WU3610 rel) from E. coli B/r strain WU3610.
- Verification of the relaxed phenotype, including RNA and ppGpp synthesis.
- Measurement and comparison of MFD kinetics between the wild-type and rel mutant strains.
Main Results:
- The constructed rel mutant displayed a typical relaxed phenotype.
- MFD kinetics were found to be identical in both the wild-type (WU3610) and the rel mutant (WU3610 rel) strains.
- The study demonstrated that stringent control is not essential for MFD.
Conclusions:
- Stringent control is not a prerequisite for mutation frequency decline in E. coli.
- The hypothesis that moderation of transcription at tRNA genes is integral to MFD is not supported by these findings.
- MFD likely operates through mechanisms independent of stringent transcriptional control at tRNA genes.