Relationship between glucosyltransferase expression and ESP production by Streptococcus mutans

Objectives:To determine the ability of different strains of S mutans to produce extracellular polysaccharides (EPS) under various conditions and to investigate the relationship between glucosyltransferase (gtf) gene expression level and EPS production in specific strains.

Methods:Twenty S mutans strains from clinical isolates and laboratory strain UA159 were selected, and their ability to produce EPS in TPY medium (initial pH 7) containing 1% glucose, 1% sucrose and 2% sucrose, respectively, was tested in triplicate. Under the same solution conditions, the relative quantities of gtfA,B,C,D's mRNA of the two strains which produced the highest and the lowest amounts of EPS were examined by real-time PCR methods.

Results:all strains, the quantity of EPS was markedly enhanced by sucrose. Clinical strain 502 produced the highest amount of EPS and UA159 produced the lowest amount. The expression levels of gtfA, B, C, and D were increased in 1% sucrose for both these strains. In 1% sucrose, the expression levels of gtfB and C of clinical strain 502 were 30% and 60% higher than those of UA159, respectively. In 2% sucrose, expression of gtfB and C decreased in UA159, whereas their expression did not change much in the clinical strain. In 1% sucrose, the expression level of gtfA was 60% higher in the clinical strain than in UA159, whilst in 2% sucrose, expression of gtfD was 3x higher in the clinical strain.

Conclusion: Expression of gtfB and C appeared closely related to EPS production by S. mutans, whilst the expression of gtfA and D may enhance EPS production in different conditions. We conclude that S mutans produces gtfs in proportions that are optimum for adhesion to the tooth surface.