Structural studies of the rhamnose-glucose polysaccharide antigen from Streptococcus sobrinus B13 and 6715-T2.

The rhamnose-glucose polysaccharide antigens from the cell walls of Streptococcus sobrinus B13 and 6715-T2 (formerly Streptococcus mutans serotypes d and g, respectively) were structurally examined by using gas chromatography-mass spectroscopy. These data confirmed earlier chemical and serological studies suggesting that these polysaccharides had identical structures. The polysaccharides appeared to have a backbone of alternating 1,2- and 1,3-linked rhamnose units. Branching occurred at 1,2,3-linked rhamnose units. Side chains appeared to be composed of 1,2- and 1,6-linked glucose units with glucose as the only terminal carbohydrate.