Related Experiment Videos
Molecular basis of bacterial adhesion in the oral cavity
S E Mergenhagen1, A L Sandberg, B M Chassy
1Laboratory of Microbiology and Immunology, National Institute of Dental Research, Bethesda, Maryland 20892.
Abstract:
The two varieties of fimbriae identified on oral strains of actinomyces have distinct functional properties. The type 1 fimbriae of Actinomyces viscosus T14V mediate attachment to saliva-treated hydroxyapatite. Type 2 fimbriae--on A. viscosus and the only fimbriae detected on A. naeslundii WVU45--are associated with lectin activity. Interaction of these fimbriae with complementary receptors initiates bacterial attachment to Streptococcus sanguis 34 and sialidase-treated epithelial cells and the killing of actinomyces by polymorphonuclear leukocytes (PMNs). Galactose, N-acetylgalactosamine (GalNAc), and related oligosaccharides inhibit these processes, and mutants lacking type 2 fimbriae do not participate in them. The actinomyces lectin is similar to lectins from Ricinus communis and Bauhinia purpurea that agglutinate certain strains of oral streptococci, block attachment of actinomyces to epithelial cells, and inhibit killing of actinomyces by PMNs. The S. sanguis receptor for the actinomyces lectin comprises repeating hexasaccharide units with GalNAc termini. Used as probes, the peanut agglutinin, with specificity for Gal(beta-3)GalNAc, and the lectin from B. purpurea detect a 160-kilodalton (kdal) band in SDS-PAGE-separated epithelial cell extracts and a 100-kdal band in PMN extracts. These may be receptors for type 2 fimbriae. A. viscosus genes encoding subunits of types 1 and 2 fimbriae have been cloned in Escherichia coli; the type 1 subunit is 65 kdal and the type 2 subunit is 59 kdal. Submandibular immunization of mice with a mixture of type 1 and type 2 fimbriae evokes the production of IgA and IgG antibodies in serum and saliva that inhibit in vitro adsorption of A. viscosus to SHA. These antibodies may modulate colonization of teeth by this organism.
Insights
Oral actinomyces have two fimbriae types. Type 2 fimbriae, with lectin activity, mediate bacterial attachment and interaction with host cells and PMNs, inhibited by specific sugars.
Area of Science:
- Microbiology
- Oral Biology
- Immunology
Background:
- Oral actinomyces possess distinct fimbriae types with varying functions.
- Type 1 fimbriae mediate attachment to saliva-treated hydroxyapatite.
- Type 2 fimbriae exhibit lectin activity, crucial for bacterial interactions.
Purpose of the Study:
- To elucidate the functional roles of type 1 and type 2 fimbriae in Actinomyces.
- To identify the molecular mechanisms underlying bacterial attachment and host interactions.
- To investigate the potential of fimbriae as targets for modulating oral colonization.
Main Methods:
- Characterization of fimbriae function in bacterial attachment assays.
- Inhibition studies using specific carbohydrates (galactose, GalNAc) and lectins.
- Identification of host cell receptors using lectin probes and SDS-PAGE.
- Gene cloning of fimbriae subunits in Escherichia coli.
- Immunization studies in mice to assess antibody responses and their effects.
Main Results:
- Type 2 fimbriae mediate attachment to Streptococcus sanguis and epithelial cells, and bacterial killing by PMNs.
- Galactose and GalNAc significantly inhibit these type 2 fimbriae-mediated processes.
- Specific lectins identified potential receptors for type 2 fimbriae on epithelial cells and PMNs.
- Cloning confirmed the molecular weights of type 1 (65 kdal) and type 2 (59 kdal) fimbriae subunits.
- Fimbriae immunization in mice generated antibodies that inhibit bacterial adhesion.
Conclusions:
- Type 2 fimbriae are key virulence factors in oral actinomyces, mediating crucial host interactions.
- The actinomyces lectin and its specific carbohydrate interactions are vital for colonization.
- Fimbriae represent promising targets for developing strategies to control oral actinomyces colonization.