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Intramolecular transposition and inversion in plasmid R6K.
Journal of Bacteriology
|May 1, 1980
Summary
Researchers identified duplicated transposon Tn2660 in ampicillin-resistant Escherichia coli strains. These duplications, often inverted, suggest intramolecular transposition events are common in plasmids like R6K.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- Plasmid R6K is a key genetic element in Escherichia coli.
- Transposons, such as Tn2660, confer antibiotic resistance.
- Understanding transposition mechanisms is crucial for antibiotic resistance research.
Purpose of the Study:
- To investigate the mechanism of ampicillin hyperresistance in Escherichia coli.
- To characterize the structure and orientation of duplicated transposons.
- To elucidate the role of intramolecular transposition in plasmid evolution.
Main Methods:
- Selection of ampicillin hyperresistant mutants in recA hosts.
- Electron microscopy and restriction enzyme analysis of mutant plasmids.
- Construction of hybrid plasmids (pSJC301, pSJC102) and transformation.
- Analysis of transposon duplication and orientation.
Main Results:
- Twenty-two strains showed duplicated transposon Tn2660, predominantly in inverted orientation.
- Intramolecular transposition of duplicated Tn2660 was inferred from studies with R6K and hybrid plasmids.
- Duplicated Tn2660 in pSJC301 caused temperature-sensitive ampicillin resistance, while in pSJC102 it conferred wild-type resistance.
- Inversion of DNA between transposons occurred frequently in R6K but rarely in pSJC102.
Conclusions:
- Duplication of Tn2660 is a mechanism for ampicillin hyperresistance.
- Intramolecular transposition is a significant event in the R6K plasmid system.
- Plasmid context influences the outcome of transposition, including DNA inversion.