Related Experiment Video

Updated: Jul 12, 2026

Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance
09:00

Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance

Published on: May 2, 2018

Plasmid pT181 replication is decreased at high levels of RepC per plasmid copy

S Iordanescu1

  • 1Public Health Research Institute, New York, New York 10016, USA.

Molecular Microbiology
|May 1, 1995
PubMed

Insights

High RepC initiator protein levels unexpectedly decreased staphylococcal plasmid pT181 replication. This plasmid replication control, dependent on RepC/origin ratio, impacts host cell division and chromosome replication.

Area of Science:

  • Molecular Biology
  • Microbiology
  • Genetics

Background:

  • Staphylococcal plasmid pT181 replication is regulated by its initiator protein, RepC.
  • High RepC levels were predicted to cause autocatalytic plasmid replication.
  • Unexpectedly, RepC overexpression affects plasmid copy number and replication rate.

Purpose of the Study:

  • To investigate the effect of RepC protein overexpression on staphylococcal plasmid pT181 replication.
  • To determine the mechanism behind the observed decrease in plasmid replication upon RepC induction.
  • To elucidate the relationship between RepC levels, plasmid origin, and replication control.

Main Methods:

  • RepC protein overexpression in Staphylococcus strains.
  • Monitoring pT181 plasmid copy number and replication rate.
  • Comparative analysis in wild-type and mutant host strains.

Main Results:

  • RepC overexpression led to a significant decrease in pT181 copy number and replication rate.
  • The inhibitory effect was dependent on the RepC to pT181 replication origin ratio, not absolute RepC concentration.
  • Host physiology, including chromosome replication and cell division, was inhibited in wild-type hosts but did not influence pT181 replication changes.

Conclusions:

  • Staphylococcal plasmid pT181 exhibits a negative feedback mechanism where RepC initiator overexpression reduces its own replication.
  • The control of pT181 replication is sensitive to the stoichiometry of RepC and the replication origin.
  • This regulatory mechanism, observed in pT181, may be conserved in other plasmids from Gram-positive bacteria.

More Related Videos

A Simple, Rapid, and Quantitative Assay to Measure Repair of DNA-protein Crosslinks on Plasmids Transfected into Mammalian Cells11:58

A Simple, Rapid, and Quantitative Assay to Measure Repair of DNA-protein Crosslinks on Plasmids Transfected into Mammalian Cells

Published on: March 5, 2018

Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach12:32

Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach

Published on: December 14, 2019

Related Concept Videos

Replication in Prokaryotes02:35

Replication in Prokaryotes

Overview
Replication in Prokaryotes02:35

Replication in Prokaryotes

Overview
Restarting Stalled Replication Forks02:37

Restarting Stalled Replication Forks

DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart, a...
Conservative Site-specific Recombination and Phase Variation02:53

Conservative Site-specific Recombination and Phase Variation

Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic engineering technique. Flippase and Cyclization recombinases or Flp and Cre, respectively, are two members of the tyrosine recombinase family derived from bacteriophages, that are used to mediate site-specific DNA insertions, deletions, and targeted expression of proteins in mammalian cell lines.
The recognition sites for Cre recombinase called LoxP...
Replication in Prokaryotes01:32

Replication in Prokaryotes

DNA replication has three main steps: initiation, elongation, and termination. Replication in prokaryotes begins when initiator proteins bind to the single origin of replication (ori) on the cell's circular chromosome. Replication then proceeds around the entire circle of the chromosome in each direction from the two replication forks, resulting in two DNA molecules.
Many Proteins Work Together to Replicate the Chromosome
Replication is coordinated and carried out by a host of specialized...
Plasmids01:28

Plasmids

Plasmids are extrachromosomal DNA molecules found in bacteria, archaea, and some eukaryotic microbes like yeast. These small, circular DNA structures typically contain fewer than 30 genes, although some may exist linearly. Plasmids vary in their number within a cell, known as copy number. Single-copy plasmids are present in one copy per cell and multi-copy plasmids are present in multiple copies, reaching over 100 copies per cell.Plasmids usually replicate independently of the chromosomal DNA...