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Characterization of the antibiotic resistance plasmid ERL1 from Streptococcus pyogenes
Abstract:
The streptococcal plasmid ERL1 determining inducible resistance to erythromycin, lincomycin, and staphylomycin S was isolated by dye-buoyant density centrifugation and shown to have a molecular weight of about 17.5 Mdal, as revealed by sedimentation through neutral sucrose gradients. In SM60 cells entering the stationary phase its covalently closed circular form was present to the extent of 5 copies per chromosomal genome equivalent, ERL1 was subject to the DNA restriction and modification mechanism discovered in strain 56188. It did not appear to exercise restriction of phage DNA but mediated a partial release of the restricted growth of A25.
Insights
The streptococcal plasmid ERL1 confers resistance to specific antibiotics. This plasmid, present in multiple copies, is influenced by bacterial DNA modification systems.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Streptococcal plasmids can confer antibiotic resistance.
- Understanding plasmid biology is crucial for combating bacterial infections.
Purpose of the Study:
- To characterize the streptococcal plasmid ERL1.
- To investigate its role in antibiotic resistance and its interaction with host cell mechanisms.
Main Methods:
- Dye-buoyant density centrifugation for plasmid isolation.
- Neutral sucrose gradient sedimentation for molecular weight determination.
- Analysis of plasmid copy number and interaction with DNA restriction systems.
Main Results:
- Plasmid ERL1, conferring resistance to erythromycin, lincomycin, and staphylomycin S, was isolated.
- Its molecular weight is approximately 17.5 Mdal.
- ERL1 exists as 5 copies per genome equivalent in stationary phase SM60 cells and is subject to strain 56188's DNA restriction/modification system.
- It did not restrict phage DNA but partially relieved phage growth restriction.
Conclusions:
- Plasmid ERL1 is a significant determinant of inducible antibiotic resistance in streptococci.
- ERL1's interaction with host DNA modification systems warrants further investigation.
- The plasmid's influence on phage growth suggests complex regulatory interactions.