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Characterization of three plasmid deoxyribonucleic acid molecules in a strain of Streptococcus faecalis:
Abstract:
Three plasmids designated alpha, beta, and gamma, distinguishable by their molecular weights (6, 17, and 34 million, respectively) were isolated from Streptococcus faecalis strain DS-5 (ATCC 14508). Derivatives of this strain "cured" for erythromycin resistance lacked the beta-plasmid. In the parent strain the beta-plasmid was estimated to be present to the extent of one to two copies per chromosomal genome equivalent whereas the alpha- and gamma-plasmids were about nine and five copies, respectively.
Insights
Researchers identified three plasmids (alpha, beta, gamma) in Streptococcus faecalis. The beta-plasmid was linked to erythromycin resistance and present in low copy numbers.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Streptococcus faecalis is a significant bacterium with various genetic elements.
- Plasmids are extrachromosomal DNA elements that can confer traits like antibiotic resistance.
Purpose of the Study:
- To characterize plasmids present in Streptococcus faecalis strain DS-5.
- To investigate the role of plasmids in erythromycin resistance.
Main Methods:
- Isolation and characterization of plasmids based on molecular weight.
- Plasmid curing experiments to assess function.
- Estimation of plasmid copy number per genome equivalent.
Main Results:
- Three plasmids (alpha, beta, gamma) with molecular weights of 6, 17, and 34 million were isolated.
- Erythromycin-sensitive derivatives of the strain lacked the beta-plasmid.
- Plasmid copy numbers were estimated: beta (1-2 copies), alpha (9 copies), and gamma (5 copies).
Conclusions:
- The beta-plasmid is associated with erythromycin resistance in Streptococcus faecalis DS-5.
- Different plasmids exhibit distinct copy number variations within the bacterial cell.