SPECIFIC AND CHARGE INTERACTIONS MEDIATE COLLAGEN RECOGNITION BY ORALLACTOBACILLI

The mechanisms by which oral lactobacilli, one of the three major gene ra of cariogenic bacteria, attach to tooth surfaces are unknown. We hy pothesize that recognition of collagen, the major component of dentin, may be a mechanism which localizes these bacteria to exposed root sur faces as well as to carious lesions which have penetrated the dentin. We found that the majority of oral Lactobacillus spp, strains recogniz e and bind collagen type I. Binding of I-125-labeled collagen type I t o two strains of L. casei rhamnosus has been characterized in some det ail. These strains were previously characterized with respect to their attachment to dentin (Switalski and Butcher, 1994). The process of I- 125-collagen binding was mediated via specific as well as charge inter actions. The putative adhesin-mediated (specific) interaction involved a limited number of bacterial surface components (2 x 10(3)/cell). Un der conditions conducive for non-specific interactions (low ionic stre ngth), the binding was higher by an order of magnitude. Collagen bindi ng strains were found to adhere to collagen-coated surfaces, while str ains unable to bind collagen adhered to a much lesser extent. Adherenc e of bacteria to collagen-coated surfaces could be competitively inhib ited with collagen. These interactions may target collagen-binding str ains of lactobacilli to dentin collagen in the oral cavity and thus pl ay a role in the pathogenesis of root surface and/or coronal caries. I nterference with this collagen-mediated attachment of lactobacilli may provide effective means of caries control, particularly in view of th e fact that other oral acidogenic microbiota also interact with collag en.