Plasmid copy number and stability determination in Clostridium perfringens transformants

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Streptococcal plasmids like pAM beta 1 are crucial for genetic studies in various bacteria.
• Understanding plasmid behavior in Clostridium perfringens is important for its genetic manipulation and biotechnological applications.

Purpose of the Study:

• To determine the copy number and stability of streptococcal plasmids (pAM beta 1 and its derivatives) in Clostridium perfringens.
• To investigate the relationship between plasmid size, copy number, and stability.

Main Methods:

• Quantification of plasmid copy number using [methyl-3H]thymidine incorporation.
• Analysis of Clostridium perfringens genome size and plasmid DNA via transverse alternating field electrophoresis.
• Assessment of erythromycin resistance retention over 220 generations to measure plasmid stability.

Main Results:

• Plasmid copy numbers for pAM beta 1, pVA1, and pVA677 were 1.0, 97, and 216 copies/cell, respectively.
• Plasmid stability, measured by erythromycin resistance retention, was 10.2%, 54%, and 96% for pAM beta 1, pVA1, and pVA677, respectively.
• A clear inverse relationship was observed between plasmid size and copy number, and a direct relationship between copy number and stability.

Conclusions:

• Plasmid stability in Clostridium perfringens is dependent on both plasmid copy number and size.
• Smaller plasmids are maintained at higher copy numbers and exhibit greater stability, facilitating their use in genetic studies.