Identification and characterization of a collagen-binding protein, Cbm, in Streptococcus mutans

Area of Science:

• Microbiology
• Oral Health
• Infectious Diseases

Background:

• Streptococcus mutans is a key pathogen in dental caries and can cause infective endocarditis.
• Bacterial attachment to collagen in damaged endothelium is crucial for infective endocarditis onset.
• Previous research identified the Cnm protein in S. mutans with collagen-binding activity.

Purpose of the Study:

• To characterize a novel collagen-binding protein, Cbm, in S. mutans strains lacking Cnm.
• To investigate the prevalence and serotype distribution of Cbm and Cnm in clinical isolates.

Main Methods:

• Characterization of the Cbm protein and sequencing of its gene (cbm).
• Construction and complementation of Cbm-deficient isogenic mutant strains.
• Analysis of clinical S. mutans isolates from Japan, Thailand, and Finland for cbm and cnm presence.

Main Results:

• A new collagen-binding protein, Cbm, with high similarity to Cnm was identified and characterized.
• Cbm-deficient mutants lost collagen-binding ability, which was restored upon complementation.
• Cbm-positive strains were found globally and in 2% of healthy subjects, predominantly in serotype k.

Conclusions:

• Cbm is a significant cell-surface protein in S. mutans involved in type I collagen binding, alongside Cnm.
• Cbm is frequently detected in serotype k strains, contributing to S. mutans pathogenicity.