The overall goal of this proposal to characterize expression of the fimbrial adhesin (FimA) of Streptococcus parasanguis FW213 at the molecular level. This protein, which is highly conserved throughout the sanguis streptococci, has been shown to be an adhesin in members of at least two of the four genetic groups of sanguis a substrate for subsequent accretion of pathogenic species. Data from several laboratories strongly suggest that ecological succession takes place in the formation and development of dental plaque, and that the sanguis (SHA) appears to be mediated by several distinct adhesins. Little is understood of the control of expression of streptococcal adhesins or the cellular pathway of streptococcal adhesin presentation. Our laboratory has recently identified an ATP-binding membrane transport system associated with FimA. We have developed an efficient method for site-specific allelic replacement mutagenesis in S. parasanguis, which greatly facilitates generic analysis of this bacterium. With these tools, our laboratory is uniquely positioned to characterize the domains of FimA involved in adhesion to the salivary pellicle and to characterize its expression and presentation on the surface of the cell. Specifically, we propose: 1. To identify other genes in the fim locus and identify its promoter. 2. To characterize the expression of proteins encoded by the fim locus. 3. To characterize the active binding domain(s) of FimA. 4. To identify additional adhesion-related genes by complementing mutations in nonadherent mutants of S. parasanguls. Molecular and genetic characterization of the adhesion of S. parasanguis to dental surfaces is now possible, with the tools developed in this laboratory. This research will contribute to the field of bacterial adhesion in the oral environment as well as to the basic understanding of the genetics of streptococci. The role of FimA-like streptococcal proteins as bifunctional adhesins involved in both initiation and multigeneric accumulation of dental plaque needs to be further studied. Our work will also explore the possible functional and evolutionary relationship between substrate binding and transport, and adhesive binding to a substrate. Therapeutic reagents resulting from studies such as the present one could have an important role in controlling dental plaque development and the subsequent disease processes.
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