Effects of dextranase on the production and degradation of extracellular glucans from Streptococcus mutans and morphological changes of S. mutans cells by dextranase treatment

A dextranase (AD17) produced by a strain of Spicaria violacea degraded commercially available dextrans to liberate glucose and various oligosaccharides including isomaltose.On the other hand, AD17 hydrolyzed the extracellular glucans of some strains of Streptococcus mutans to a limited degree. Only 15 to 36 percent of the total polysaccharides were consumed by AD17 with little release of isomaltose. AD17, however, inhibited the formation of artificial dental plaques which developed in sucrose-containing broth by serial transfer of S. mutans. Changes in cell morphology due to AD17 treatment were revealed by scanning electron micrography. S. mutanscells grown in sucrose-containing broth were coated with sticky capsular materials, whereas cells grown in sucrose in the presence of AD17 or glucose-containing broth did not show such gel-like structure.These differences indicate the importance of glycosidic linkages which are susceptible to AD17 in the adherence of S. mutans cells to free surface.