Plasmid deoxyribonucleic acid in Bacillus subtilis and Bacillus pumilus

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Plasmids are extrachromosomal DNA elements found in bacteria.
• Characterizing plasmids is crucial for understanding bacterial genetics and evolution.
• Bacillus subtilis is a well-studied model organism in microbiology.

Purpose of the Study:

• To identify and characterize plasmids in Bacillus subtilis strains.
• To determine the molecular weight and copy number of identified plasmids.
• To assess the genetic relatedness of strains harboring plasmids.

Main Methods:

• Screening of eighteen Bacillus subtilis strains for covalently closed circular DNA.
• Isolation and characterization of plasmid DNA using techniques like buoyant density centrifugation.
• Estimation of plasmid molecular weights.
• Genetic, physiological, and biochemical analysis of bacterial strains.

Main Results:

• Two Bacillus subtilis strains, ATCC 15841 and ATCC 7003, were found to contain plasmids.
• Strain ATCC 15841 harbored plasmid pPL1 (approx. 4.7 x 10^6 MW, 16 copies/chromosome).
• Strain ATCC 7003 contained plasmid pPL2 (approx. 46 x 10^6 MW, 1-2 copies/chromosome).
• Bacillus pumilus ATCC 12140 contained two plasmids, pMB1 (approx. 6.8 x 10^6 MW) and pMB2 (approx. 5.3 x 10^6 MW).
• Strain ATCC 7003 showed close relation to B. subtilis 168, while ATCC 15841 was less related.

Conclusions:

• The study identified novel plasmids in Bacillus subtilis and Bacillus pumilus strains.
• Plasmid characteristics, including size and copy number, vary significantly between strains.
• The genetic relatedness of strains correlates with their plasmid content and characteristics.