Modulation of covR expression in Streptococcus mutans UA159

Area of Science:

• Microbiology
• Molecular Biology
• Dental Research

Background:

• Streptococcus mutans causes dental caries.
• CovR is a key regulator for S. mutans pathogenesis and biofilm formation.
• CovR is an orphan response regulator, and its expression regulation is unknown.

Purpose of the Study:

• To investigate factors regulating covR expression in S. mutans UA159.
• To elucidate the autoregulation mechanism of CovR.
• To understand the role of environmental factors in covR expression.

Main Methods:

• Southern hybridization and PCR analysis to identify CovR as an orphan regulator.
• Site-directed mutagenesis to confirm the TATAAT box.
• Semiquantitative reverse transcriptase PCR and transcriptional-fusion reporter assays.
• Electrophoretic mobility shift assays and DNase I protection assays for binding analysis.

Main Results:

• CovR expression is growth phase-dependent, peaking during exponential growth.
• Increased pH and Mg(2+) concentration enhance covR expression.
• CovR directly binds to its promoter region, confirming autoregulation.
• Mg(2+) regulation and autoregulation are independent processes.

Conclusions:

• CovR autoregulates its own expression in S. mutans.
• CovR expression is modulated by growth phase, pH, and Mg(2+) levels.
• Further study of CovR regulation can inform strategies for preventing dental caries.