Related Experiment Videos
Streptococcus faecalis sex pheromone (cAM373) also produced by Staphylococcus aureus and identification of a
Abstract:
Streptococcus faecalis RC73 was found to harbor a conjugative plasmid (pAM373) which confers a mating response to a sex pheromone (cAM373) excreted by plasmid-free members of the same species. The pheromone was also detected in culture filtrates of all of 23 Staphylococcus aureus strains but in only 2 of 22 coagulase negative staphylococcus strains. Streptococcus sanguis Challis and G9B also produced the activity, but 10 other Streptococcus sanguis strains did not. The activity was also produced by Streptococcus faecium 9790. A tetracycline resistance (Tc) determinant present in S. faecalis RC73 was not associated with pAM373 but served as a useful marker in efforts to identify pAM373 among other plasmids present in the strain. Analyses of the Tc determinant showed that it was located on a conjugative transposon very similar to Tn916. Designated Tn918, the transposon could insert into pAM373 as well as into two other hemolysin plasmids. Whereas pAM373 derivatives transferred very well between strains of Streptococcus faecalis, the plasmid would not establish in Staphylococcus aureus or Streptococcus sanguis. However, a derivative of pAM373 carrying Tn918 proved to be a useful delivery vehicle for generating transposon insertions into multiple sites on the staphylococcal chromosome.
Insights
A conjugative plasmid, pAM373, in Streptococcus faecalis responds to sex pheromones. This plasmid, along with transposon Tn918, facilitated genetic transfer studies in staphylococcal strains.
Area of Science:
- Microbiology
- Bacterial Genetics
- Plasmid Biology
Background:
- Conjugative plasmids facilitate genetic exchange in bacteria.
- Sex pheromones are key mediators of plasmid transfer in some bacterial species.
- Understanding plasmid-plasmid and plasmid-chromosome interactions is crucial for bacterial genetics.
Purpose of the Study:
- To characterize the conjugative plasmid pAM373 from Streptococcus faecalis.
- To investigate the role of sex pheromones in plasmid conjugation.
- To explore the utility of pAM373 and associated genetic elements for manipulating staphylococcal genomes.
Main Methods:
- Plasmid isolation and characterization.
- Detection of pheromone activity in various bacterial species.
- Conjugation experiments to assess plasmid transfer and stability.
- Analysis of transposon Tn918 integration and function.
Main Results:
- Streptococcus faecalis RC73 harbors conjugative plasmid pAM373, which responds to sex pheromone cAM373.
- Pheromone activity was detected in Staphylococcus aureus and some Streptococcus species.
- A tetracycline resistance transposon, Tn918, was identified and shown to insert into pAM373 and other plasmids.
- pAM373 derivatives transferred efficiently in S. faecalis but not in S. aureus or S. sanguis.
- A pAM373 derivative carrying Tn918 served as a vehicle for generating transposon insertions in Staphylococcus.
Conclusions:
- The conjugative plasmid pAM373 plays a role in pheromone-mediated mating in Streptococcus faecalis.
- The transposon Tn918 can be mobilized by pAM373 and is useful for generating genomic mutations in staphylococci.
- pAM373 and Tn918 represent valuable tools for studying bacterial conjugation and genome manipulation.