Comprehensive characterization of sortase A-dependent surface proteins in Streptococcus mutans.

Area of Science:

• Microbiology
• Oral Health
• Bacterial Pathogenesis

Background:

• Streptococcus mutans causes tooth decay by forming biofilms.
• Bacterial cell surface proteins are key for adherence.
• Sortase A (SrtA) anchors surface proteins via covalent binding to peptidoglycan.

Purpose of the Study:

• To comprehensively analyze the roles of six SrtA-dependent proteins (SpaP, WapA, WapE, DexA, FruA, GbpC) in Streptococcus mutans.
• To investigate the impact of SrtA deficiency and individual SrtA-dependent protein deficiencies on bacterial phenotypes.

Main Methods:

• Construction of SrtA-deficient and individual SrtA-dependent protein-deficient mutants of S. mutans UA159.
• Phenotypic analysis including salivary component binding, biofilm formation, coaggregation, hydrophobicity, and matrix binding.
• Comparative genomic analysis of surface protein sequences across 125 S. mutans strains.

Main Results:

• SrtA-deficient mutants exhibited severely reduced salivary binding, biofilm formation, coaggregation, hydrophobicity, and matrix binding.
• SpaP-deficient mutants showed reduced salivary binding, decreased hydrophobicity, and altered coaggregation.
• Most individual SrtA-dependent protein mutants, except SpaP, showed minimal changes in salivary binding, suggesting coordinated function.

Conclusions:

• The six SrtA-dependent proteins likely work together to mediate S. mutans adherence and biofilm formation.
• Variations in surface protein sequences across different S. mutans strains may influence their functional phenotypes.