Streptococcus mutans genes that code for extracellular proteins in Escherichia coli K-12

Area of Science:

• Microbiology
• Molecular Biology
• Immunology

Background:

• Streptococcus mutans is a key bacterium in dental caries.
• Understanding its surface antigens is crucial for vaccine development.

Purpose of the Study:

• To clone and characterize the gene encoding the spaA surface protein antigen from Streptococcus mutans.
• To investigate the expression and antigenic properties of the spaA protein in E. coli.

Main Methods:

• Cloning of Streptococcus mutans chromosomal DNA into E. coli using cosmid vectors.
• Immunological screening of bacterial clones using specific antisera.
• Plasmid isolation, DNA fragment subcloning, and SDS-PAGE analysis.
• Characterization of expressed polypeptide localization within E. coli cells.

Main Results:

• A recombinant plasmid, pYA726, containing the spaA gene was constructed.
• The cloned gene expressed a 180,000-dalton polypeptide primarily in the periplasmic space.
• Immunological studies confirmed the identity of the expressed protein as spaA, with some differences in antigenic determinants.
• The spaA protein's antigenicity was confirmed across multiple S. mutans serotypes, excluding serotype b.

Conclusions:

• The gene for the Streptococcus mutans spaA surface protein antigen has been successfully cloned and expressed in E. coli.
• The expressed protein shares antigenic determinants with native spaA and is found in the periplasmic space.
• This research provides a foundation for further studies on spaA's role in S. mutans and potential vaccine strategies.