Molecular Basis of the Ecology of Oral Streptococci

Rosan, Burton

Abstract

The exquisite specificity of the oral streptococci for different ecological niches within the oral cavity appears to be directly related to differences in their surfaces. Some of the differences may be directly observed at the ultrastructural level which indicates that the """"""""fuzzy"""""""" coats (fimbriae) of Streptococcus salivarius which colonize epithelial cell surfaces are much longer than the fimbriae of S. sanguis, S. mitis or S. mutans which colonize tooth surfaces. Although the exact role of these fimbriae on surface structures in determining the particular ecological niche is not known, it is clear that these surfaces are involved in interactions with salivary pellicle resulting in plaque formation, saliva mediated bacterial aggregation, attachment to opithelial cells and interactions with other oral bacteria, e.g., corn cob formation. Thus, differences in the macromolecular composition of surfaces of the oral streptococci can be utilized as a model for the expression of differences in their ability to attach to different tissues. The attachment of bacteria to tissues appears to be the primary event in the initiation of many infectious diseases, including dental caries and periodontal disease. The objectives of the proposed studies are to develop a profile of the polysaccharide, teichoic acid and protein components of the surfaces of the oral streptococci using a combination of isotopic labeling techniques and analytical electro- phoretic methods. Using these profiles or """"""""maps"""""""" as a guide, an investigation of the molecular basis of specificity for adherence will be undertaken employing strains of species which have different adherence properties, isogenic mutants and phenotypically altered cells. Extracts of these strains should give altered macromolecular profiles of their surfaces and thus provide the clues as to which molecules are associated with adherence. These molecules will be isolated, characterized chemically and immunochemically and studies of the cellular localization using immunohistochemistry will be undertaken. Finally, monospecific antiserum will be used to determine if adherence to oral tissues can be inhibited. These studies will provide a molecular taxonomy for the surfaces of oral streptococci which could be used as a basis for monitoring the effects of environment, antibody interaction, mutation and genetic transfer on the surfaces of oral streptococci.