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ComX activity of Streptococcus mutans growing in biofilms
Marcelo B Aspiras1, Richard P Ellen, Dennis G Cvitkovitch
1Faculty of Dentistry, University of Toronto, 124 Edward Street, Toronto, Ont., Canada M5G 1G6.
FEMS Microbiology Letters
|September 1, 2004
Summary
Competence stimulating peptide (CSP) activates comX gene expression in Streptococcus mutans, enhancing natural transformation and competence development within biofilms. This quorum sensing system is crucial for bacterial adaptation and genetic exchange in oral biofilms.
Area of Science:
- Microbiology
- Bacterial genetics
- Quorum sensing
Background:
- Streptococcus mutans utilizes quorum sensing for genetic competence, influenced by competence stimulating peptide (CSP).
- The comX gene encodes a sigma factor critical for activating competence genes in Streptococcus pneumoniae.
- In S. mutans, quorum sensing links genetic competence to biofilm formation and acid tolerance.
Purpose of the Study:
- To investigate the regulatory role of CSP on comX gene expression in Streptococcus mutans.
- To correlate comX activity with natural transformation and competence development in S. mutans biofilms.
Main Methods:
- Constructed transcriptional fusions of the comX promoter (pcomX) with lacZ and green fluorescent protein (GFP) reporters.
- Transformed reporter constructs into CSP-deficient S. mutans strains.
- Measured beta-galactosidase activity and GFP fluorescence in response to CSP addition and during biofilm development.
- Assessed natural transformation frequency in biofilm-grown cells.
Main Results:
- CSP addition induced a 2-fold increase in pcomX::lacZ expression within 5-10 minutes.
- Peak pcomX activity and maximal transformation frequency in biofilms occurred at 3 hours.
- Confocal microscopy revealed high comX activity in dense cell areas within 4-hour biofilms.
- Demonstrated a positive correlation between pcomX activity, natural transformation, and competence.
Conclusions:
- ComX expression is positively regulated by CSP in Streptococcus mutans.
- ComX activation is temporally linked to natural transformation and competence development in S. mutans biofilms.
- This study elucidates a key mechanism for genetic exchange and adaptation in oral biofilms.
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