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Expression of Streptococcus mutans gtf genes in Streptococcus milleri
K Fukushima1, T Ikeda, H K Kuramitsu
1Department of Microbiology, School of Dentistry at Matsudo, Nihon University, Chiba, Japan.
Infection and Immunity
|July 1, 1992
Summary
Streptococcus mutans glucosyltransferase (GTF) genes gtfB and gtfC were expressed in Streptococcus milleri. These genes produced enzymes that synthesized glucans, with gtfC transformants showing cell adhesion, suggesting a role in S. mutans cariogenicity.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Streptococcus mutans is a primary causative agent of dental caries.
- Glucosyltransferases (GTFs) produced by S. mutans synthesize glucans, contributing to biofilm formation and cariogenicity.
- The specific roles of individual GTF genes, such as gtfB and gtfC, in S. mutans virulence are not fully elucidated.
Purpose of the Study:
- To investigate the functional expression of Streptococcus mutans glucosyltransferase (GTF) genes gtfB and gtfC in a heterologous host, Streptococcus milleri.
- To characterize the enzymatic properties and biological activities of GTFs produced from gtfB and gtfC.
- To assess the potential contribution of gtfB and gtfC to S. mutans cariogenicity based on observed phenotypes.
Main Methods:
- Ligation of gtfB and gtfC genes into shuttle plasmids for transformation into Streptococcus milleri.
- Cultivation of transformants and analysis of colony morphology on mitis salivarius agar.
- Purification and biochemical characterization of extracellular GTFs, including enzyme activity assays and substrate specificity analysis.
- Assessment of cell adhesion to glass surfaces in vitro.
Main Results:
- Expression of gtfB in S. milleri resulted in rough colonies and production of extracellular and cell-bound GTF-I enzymes.
- Expression of gtfC yielded semirough colonies and primarily extracellular GTF-SI enzymes.
- Both GTF-I and GTF-SI synthesized oligosaccharides and water-insoluble glucans, with similar kinetic properties and optimal pH.
- GTF-SI-producing cells (from gtfC) exhibited adherence to glass, unlike GTF-I-producing cells (from gtfB).
Conclusions:
- The gtfB and gtfC genes encode functional glucosyltransferases capable of producing glucans and influencing cell surface properties.
- The differential cell adhesion observed between gtfB and gtfC transformants suggests distinct roles for these enzymes in S. mutans biofilm formation and virulence.
- These findings support the hypothesis that gtfB and gtfC play significant roles in the cariogenic potential of Streptococcus mutans.