[Construction of a low-pH-sensing system in Streptococcus mutans]

Area of Science:

• Microbiology
• Molecular Biology
• Biotechnology

Background:

• Streptococcus mutans (S. mutans) is a key bacterium in dental caries, thriving in acidic environments.
• Accurate in situ pH monitoring is crucial for understanding cariogenic processes.
• Existing methods for pH detection in biofilms can be invasive or lack real-time visualization.

Purpose of the Study:

• To engineer a functional low-pH-sensing system within S. mutans.
• To enable visual, in situ detection of pH changes.
• To validate the efficacy of a specific promoter in response to acidic conditions.

Main Methods:

• Amplification of urease I promoter (Pure I) and green fluorescence protein (GFP) DNA fragments via PCR.
• Ligation of Pure I and GFP fragments and integration into the pDL278 plasmid.
• Transformation of the recombinant plasmid (pDL278-pure I-gfp) into S. mutans UA159.
• Measurement of optical density to quantify fluorescence intensity under varying pH and time conditions.

Main Results:

• Successful amplification and verification of Pure I and GFP DNA fragments.
• Construction and confirmation of the recombinant plasmid pDL278-pure I-gfp.
• Demonstrated correlation between decreased pH, increased processing time, and enhanced fluorescence intensity.

Conclusions:

• A functional low-pH-sensing system was successfully constructed in S. mutans.
• The urease I promoter from Streptococcus salivarius effectively functions as an acid-induced promoter in S. mutans.
• This system provides a novel approach for in situ pH detection in dental plaque biofilms.