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Why does Staphylococcus aureus secrete an Enterococcus faecalis-specific pheromone?
A Muscholl-Silberhorn1, E Samberger, R Wirth
1Universität Regensburg, NWF III-Mikrobiologie, Germany. Albrecht.Muscholl@biologie.uni-regensburg.de
Abstract:
The long known fact that Staphylococcus aureus can secrete a peptide (staph-cAM373) which acts as a sex pheromone for strains of E. faecalis carrying the sex pheromone plasmid pAM373 was studied in detail. 85 of 100 independent isolates of S. aureus produced an activity inducing the pAM373 encoded adhesin resulting in a clumping reaction of E. faecalis (i.e. secreted staph-cAM373), but not a single one of 100 independent isolates of coagulase-negative Staphylococci possessed this activity. The production of peptides acting as sex pheromone for E. faecalis was observed only for sex pheromone plasmid pAM373, but not for sex pheromone plasmids pAD1 and pPD1. It was shown that the amount of staph-pAM373 produced during growth paralleled cell mass, therefore this peptide should not be used as a cell density indicator by S. aureus (i.e. has no quorum sensing function). The potential function of staph-cAM373 to trigger gene transfer from Escherichia faecalis to S. aureus is discussed.
Insights
Staphylococcus aureus secretes staph-cAM373, a sex pheromone for E. faecalis. This peptide production is specific to S. aureus strains with the pAM373 plasmid, not coagulase-negative staphylococci.
Area of Science:
- Microbiology
- Bacteriology
- Molecular Biology
Background:
- Staphylococcus aureus produces staph-cAM373, a peptide functioning as a sex pheromone for Enterococcus faecalis strains harboring the pAM373 plasmid.
- This interaction involves the induction of a specific adhesin encoded by the pAM373 plasmid in E. faecalis, leading to cell clumping.
Purpose of the Study:
- To investigate the prevalence and specificity of staph-cAM373 production in Staphylococcus species.
- To determine the relationship between staph-cAM373 production and bacterial growth or cell density.
- To explore the potential role of staph-cAM373 in interspecies gene transfer.
Main Methods:
- Screening of independent isolates of Staphylococcus aureus and coagulase-negative staphylococci for pheromone-inducing activity.
- Assaying for the production of staph-cAM373 by quantifying its effect on E. faecalis clumping.
- Comparing staph-cAM373 production levels with bacterial cell mass during growth.
Main Results:
- 85% of S. aureus isolates produced staph-cAM373, while none of the coagulase-negative staphylococci isolates did.
- Staph-cAM373 production was specific to the pAM373 plasmid and not observed with pAD1 or pPD1 plasmids.
- Staph-cAM373 production correlated with cell mass, indicating it does not function as a quorum sensing molecule.
Conclusions:
- Staph-cAM373 production is a characteristic of specific Staphylococcus aureus strains carrying the pAM373 plasmid.
- The peptide's production is not linked to quorum sensing in S. aureus.
- Further research is warranted to understand staph-cAM373's role in facilitating gene transfer between E. faecalis and S. aureus.