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Cell surface polypeptide CshA mediates binding of Streptococcus gordonii to other oral bacteria and to immobilized
R McNab1, A R Holmes, J M Clarke
1Department of Oral Biology and Oral Pathology, University of Otago, Dunedin, New Zealand.
Abstract:
Isogenic mutants of Streptococcus gordonii DL1 (Challis) in which the genes encoding high-molecular-mass cell surface polypeptides CshA and/or CshB were inactivated were deficient in binding to four strains of Actinomyces naeslundii and two strains of Streptococcus oralis. Lactose-sensitive interactions of S. gordonii with A. naeslundii ATCC 12104 and PK606 were associated with expression of cshA but not of cshB. Lactose-insensitive interactions of S. gordonii with A. naeslundii T14V and WVU627, and with S. oralis C104 and 34, were dependent on expression of cshA and cshB. S. gordonii DL1 cells bound to immobilized human fibronectin (Fn), but not to soluble Fn, in a dose-dependent manner, and binding was noninhibitable by heparin. S. gordonii cshA and cshB mutants were also deficient in binding to immobilized human Fn. Antibodies to an NH2-terminal nonrepetitive region (amino acid residues 42 to 886) of recombinant CshA inhibited binding of S. gordonii DL1 cells to A. naeslundii T14V and PK606 and to immobilized Fn. Conversely, antibodies to an amino acid repeat block segment of the COOH-terminal domain (amino acid residues 2026 to 2508) were not inhibitory to adherence. Assays using CshA-specific antibodies revealed that surface expression of CshA was reduced in cshB mutants. The results suggest that CshA acts as a multifunctional adhesin in S. gordonii and that major adhesion-mediating sequences are specified within the nonrepetitive NH2-terminal region of the polypeptide.
Insights
Streptococcus gordonii uses cell surface proteins CshA and CshB to adhere to other bacteria and human fibronectin. CshA is a key adhesin, with its N-terminal region crucial for mediating these interactions.
Area of Science:
- Microbiology
- Oral Health
- Bacterial Adhesion
Background:
- Streptococcus gordonii is a key commensal bacterium in the oral cavity.
- Bacterial adhesion is crucial for colonization and biofilm formation.
- Cell surface proteins play vital roles in mediating interspecies and host-bacterial interactions.
Purpose of the Study:
- To investigate the role of high-molecular-mass cell surface polypeptides CshA and CshB in Streptococcus gordonii adhesion.
- To determine the specific domains of CshA involved in mediating interactions with Actinomyces naeslundii, Streptococcus oralis, and human fibronectin.
Main Methods:
- Construction and analysis of isogenic mutants of Streptococcus gordonii lacking CshA and/or CshB.
- Adhesion assays using various bacterial strains and immobilized human fibronectin.
- Inhibition assays using antibodies targeting specific regions of CshA.
Main Results:
- Mutants lacking CshA and/or CshB showed reduced binding to Actinomyces naeslundii and Streptococcus oralis strains.
- Lactose-sensitive binding was associated with CshA expression, while lactose-insensitive binding required both CshA and CshB.
- Streptococcus gordonii binding to immobilized fibronectin was dependent on CshA and CshB.
- Antibodies against the N-terminal region of CshA inhibited bacterial adhesion to A. naeslundii and fibronectin.
Conclusions:
- CshA functions as a multifunctional adhesin in Streptococcus gordonii.
- The N-terminal nonrepetitive region of CshA contains critical sequences for adhesion.
- CshB influences the surface expression of CshA, contributing to overall bacterial adherence.