[A low copy number mutant of pUC-derived plasmid]

Area of Science:

• Molecular Biology
• Microbiology
• Genetics

Background:

• ColE1-like plasmids are crucial tools in molecular biology but can exhibit instability in host strains.
• Recombinant plasmid pPGVT3, derived from pUC4, showed instability and failed transformation at elevated temperatures in Escherichia coli DF2145.
• Plasmid instability limits their utility in genetic engineering and biotechnology.

Purpose of the Study:

• To generate a stable low copy number mutant of the ColE1-like plasmid pPGVT3.
• To investigate the effect of induced mutations on plasmid stability and copy number.
• To understand the relationship between plasmid copy number and recombinant plasmid stability in Escherichia coli.

Main Methods:

• In vitro mutagenesis of pPGVT3 plasmid DNA using hydroxylamine to induce point mutations.
• Transformation of Escherichia coli host strain DF2145 with wild-type and mutant plasmids.
• Assessment of plasmid stability and copy number in transformed host strains at different temperatures.

Main Results:

• A mutant plasmid, pPGVT3HA, was successfully generated exhibiting enhanced stability in E. coli DF2145.
• The mutation was localized within the pUC moiety of the pPGVT3HA plasmid.
• The copy number of the mutated pUC vector and its derivatives was significantly reduced.
• Plasmid stability was improved in the low copy number mutant.

Conclusions:

• Induced point mutations can create stable, low copy number plasmid mutants.
• Reducing plasmid copy number is an effective strategy to enhance recombinant plasmid stability.
• The findings provide insights into plasmid replication control and stability mechanisms in Escherichia coli.