The use of lectins in monitoring degradation of oligosaccharide chains in mucin by oral streptococci.

The ability of utilize mucin oligosaccharides as sources of carbohydrate and energy is believed to be an important mechanism in the ecology of oral streptococci. In this study we have used digoxigenin-labelled lectins of various specificities to monitor changes in the nonreducing end groups of oligosaccharide chains following their degradation by Streptococcus oralis Ny 586 and Streptococcus sanguis Ny 584. The reaction of degraded mucin with peanut lectin, that recognizes the core disaccharide Gal (1,3)GalNAc in O-glycans, revealed a more extensive degradation of oligosaccharide by S. oralis than by S. sanguis. This corresponds to better growth of S. oralis on the mucin. Analyses with Datura stramonium lectin showed that terminal Gal (1,4)GlcNAc, or GlcNAc (1,4)GlcNAc moieties, in the oligosaccharides are attacked by both strains. Reaction patterns with alpha-L-fucose-specific lectins indicated that terminal fucose was released by S. oralis but not by S. sanguis. This was in accordance with sugar analyses which showed that approximately 40% of the fucose units were released. The results extend previously observed losses of sugars from oligosaccharide chains during growth of these organisms on mucin.