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Hemolysin plasmid coding for the virulence of a nephropathogenic Escherichia coli strain
Abstract:
The nephropathogenic Escherichia coli strain P673 was shown to harbor two plasmids with molecular sizes of 70 and 41 megadaltons, respectively. The 70-megadalton plasmid, pCW1, coded for tetracycline resistance, whereas hemolysin production was coded by the 41-megadalton plasmid, pCW2. Plasmid pCW1 proved to be self-transmissible, in contrast to pCW2. Transfer of the hemolysin character was associated with the appearance of a 110-megadalton plasmid, pCW3. The incompatibility of pCW3 with both native plasmids and restriction enzyme analysis led to the conclusion that pCW3 is a cointegrate of pCW1 and pCW2, pCW2, carrying the hemolytic determinant, is involved in the nephropathogenic character of strain P673, because (i) elimination of pCW2 from P673 was associated with a loss of virulence and (ii) the nephropathogenicity of the avirulent mutant could be restored by reintroduction of pCW2 DNA as part of a cointegrate structure.
Insights
Nephropathogenic Escherichia coli strain P673 harbors two plasmids. Plasmid pCW2, responsible for hemolysin production, is crucial for virulence in this E. coli strain.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Nephropathogenic Escherichia coli (E. coli) strains cause significant kidney infections.
- Plasmids are extrachromosomal DNA elements that often carry virulence factors and antibiotic resistance genes.
- Understanding the genetic basis of pathogenicity in E. coli is crucial for developing effective treatments.
Purpose of the Study:
- To characterize the plasmids harbored by the nephropathogenic E. coli strain P673.
- To determine the role of specific plasmids in hemolysin production and virulence.
- To investigate the genetic mechanisms underlying the nephropathogenic nature of E. coli P673.
Main Methods:
- Plasmid isolation and molecular size determination.
- Analysis of plasmid-encoded traits, including tetracycline resistance and hemolysin production.
- Plasmid transfer experiments and incompatibility studies.
- Restriction enzyme analysis of plasmid DNA.
- Virulence assays in an appropriate model system.
Main Results:
- Strain P673 contains two plasmids: pCW1 (70 megadaltons) conferring tetracycline resistance and pCW2 (41 megadaltons) encoding hemolysin production.
- Plasmid pCW1 is self-transmissible, while pCW2 is not.
- Transfer of hemolysin production resulted in a cointegrate plasmid, pCW3 (110 megadaltons), formed from pCW1 and pCW2.
- Elimination of pCW2 led to a loss of virulence, which could be restored by reintroducing pCW2 DNA.
Conclusions:
- Plasmid pCW2, carrying the hemolytic determinant, is directly involved in the nephropathogenic character of E. coli strain P673.
- The hemolysin produced by pCW2 is a key virulence factor contributing to kidney infections.
- Cointegrate formation involving pCW1 and pCW2 facilitates the maintenance and transfer of virulence traits.