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Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance
Published on: May 2, 2018
A "retrocidal" plasmid in Enterococcus faecalis: passage and protection.
Susan E Flannagan1, Don B Clewell, Christine M Sedgley
1Cariology, Restorative Sciences and Endodontics, School of Dentistry, 1011 N. University Avenue, Ann Arbor, MI 48109-1078, USA.
Plasmid
|February 26, 2008
Summary
A novel plasmid enables Enterococcus faecalis to produce bacteriocins against its own strain, demonstrating a unique "retrocidal" effect. This discovery offers insights into bacterial gene regulation and evolution.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Enterococcus faecalis MC4 possesses a conjugative plasmid, pAMS1, conferring antibiotic resistance.
- The plasmid contains a bacteriocin determinant (MC4-1) and immunity gene, but these were not expressed in the original host.
Purpose of the Study:
- To investigate the expression and function of the bacteriocin determinant on the conjugative plasmid pAMS1.
- To understand the "retrocidal" activity observed after plasmid transfer and the host's defense mechanisms.
Main Methods:
- Conjugative transfer of plasmid pAMS1 to different Enterococcus faecalis strains.
- Assaying bacteriocin activity against plasmid donor and other bacterial species.
- Determining the frequency of bacteriocin resistance and sensitivity switching.
Main Results:
- Plasmid pAMS1 transfer induced bacteriocin expression targeting the plasmid donor (MC4) in E. faecalis JH2-2.
- The bacteriocin exhibited a broad spectrum, including Enterococcus species and Listeria monocytogenes.
- A plasmid-independent defense mechanism involving a switch to bacteriocin resistance was observed in susceptible strains.
Conclusions:
- Conjugative plasmids can carry genes that confer "retrocidal" properties, impacting bacterial populations.
- The observed defense mechanism suggests a novel, plasmid-independent strategy for bacterial self-protection.
- These findings have implications for understanding bacterial gene regulation, plasmid evolution, and ecological dynamics.
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