Adhesion of a bacterial pathogen to its target surface is a critical step in establishing an infection in many disease processes, including dental caries. Adhesion of oral bacteria to tooth surfaces has been proposed to occur via fimbriae-mediated interactions. Fimbrial protein preparations from Streptococcus mutans contain several proteins (55 kDa, 59 kDa, 65 kDa, 116 kDa, 210 kDa). This lab has previously shown that the 65 kDa S. mutans fimbrial protein binds to salivary amylase. Objectives: To clone and characterize the 65 kDa fimbrial protein of S. mutans. Methods: A library of S. mutans chromosomal DNA was cloned into lambda EMBL3. Positive clones were identified by probing plaque lifts with antibody to the 65 kDa S. mutans fimbrial protein. The size of the streptococcal proteins produced in E. coli was determined by PAGE electrophoresis followed by immunoblotting with anti-S. mutans antibodies. Results: We report the cloning of the DNA encoding the 65 kDa S. mutans fimbrial protein on a 15 kb SalI fragment in lambda EMBL3. The cloned DNA produces a 65 kDa protein in E. coli that reacts specifically with antibody to the 65 kDa S. mutans fimbrial protein. The 15 kb insert has been characterized by restriction mapping and is being subcloned for further characterization by sequencing and antibody reactivity. This clone produces at least three additional S. mutans proteins (40 kDa, 55 kDa, and 116 kDa) in E. coli, detectable using anti-whole cell S. mutans or anti-crude fimbrial antibodies. Conclusions: The 65 kDa S. mutans fimbrial protein has been cloned on a 15 kb DNA fragment. Multiple S. mutans fimbrial proteins are located within the same 15 kb fragment of cloned DNA. This suggests the possibility of coordinated expression of these proteins on the bacterial chromosome.

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