Sucrose selectively regulates Streptococcus mutans polysaccharide by GcrR

Area of Science:

• Microbiology
• Molecular Biology
• Dental Research

Background:

• Streptococcus mutans is the primary cause of dental caries.
• Sucrose metabolism into extracellular polysaccharides (EPS) by S. mutans drives cariogenesis.
• GcrR and VicR are response regulators with opposing roles in EPS metabolism, but their interaction is unclear.

Purpose of the Study:

• To elucidate the cooperative interactions between GcrR and VicR in regulating sucrose-selective EPS metabolism.
• To investigate the role of GcrR in controlling EPS production and biofilm formation.
• To identify potential therapeutic targets for managing dental caries.

Main Methods:

• Construction and analysis of various dual-mutant strains of S. mutans (overexpression, deletion, low-expression).
• Quantification of gtfB/gtfC gene expression levels under different GcrR and VicR conditions.
• Assessment of bacterial auto-aggregation and biofilm formation.
• Analysis of dexA gene expression and GcrR binding to the dexA promoter region.

Main Results:

• GcrR modulates gtfB/gtfC expression independently of VicR.
• GcrR deletion leads to increased auto-aggregation and EPS production in the presence of sucrose.
• GcrR acts as a sucrose-inducible 'switch-off' regulator for EPS biosynthesis.
• GcrR directly binds to the dexA promoter, enhancing its expression and leading to polysaccharide digestion.

Conclusions:

• GcrR and VicR cooperate to inhibit EPS biosynthesis through sucrose-selective polysaccharide digestion mediated by DexA.
• Targeting GcrR presents a promising strategy for controlling S. mutans virulence and preventing dental caries.