PROPERTIES OF A VARIANT OF STREPTOCOCCUS-MUTANS ALTERED IN ITS ABILITY TO INTERACT WITH GLUCANS

After continuous subculture of S. mutans GS-5, the resultant organism, GS-5var, was altered in its ability to undergo dextran- and sucrose-induced cell agglutination and to adhere to smooth surfaces in the presence of sucrose. GS-5 and GS-5var cells p possessed the serotype c polysaccharide antigen, displayed similar growth kinetics, appeared to have similar metabolic and biosynthetic capabilities and produced similar amounts of cell-associated and extracellular glucosyltransferase activity in chemically defined medium. GS-5 cells which bound exogenous glucosyltransferase enzymes from either cell type underwent sucrose-dependent adherence to smooth surfaces; GS-5var cells which bound comparable levels of glucosyltransferase activity were unable to adhere. In contrast to GS-5var cells, GS-5 cells were able to adhere to preformed glucan deposits. [14C]glucan binding studies demonstrated that GS-5 cells were able to bind 4-fold-greater levels of [14C]glucan relative to GS-5var cells having similar cell-associated glucosyltransferase activity. Further study of GS-5 cells suggested the existence of a glucan binding site, distinct from the cell-associated glucosyltransferase activity, which is important in dextran-induced agglutination and sucrose-dependent adherence to smooth surfaces. These results are discussed in terms of the alteration of the GS-5var cells and their possible relationship to the putative receptors for glucosyltransferase enzymes and glucans on the cell surface of S. mutans [factors which have relevance to the cariogenicity of this organism].