Structure of extracellular water-soluble polysaccharides synthesized from sucrose by oral strains of Streptococcus mutans, Streptococcus salivarius, Streptococcus sanguis and Actinomyces viscosus

Abstract

Extracellular water-soluble polysaccharides produced from sucrose by various strains of oral streptococci and one strain of Actinomyces viscosus were isolated and analysed. Methylation analysis and characterization of the cleavage products by gas-liquid chromatogra-phy-mass spectrometry were the principal methods used. Streptococcus salivarius ATCC 9759, ATCC 13419 and NCTC 8618 and A. viscosus ATCC 15987 synthesized fructans of the levan-type with (2 → 6)-linked β-fructofuranoside residues, branched in the 1-position (15–17 per cent) and of high molecular weight (2.7 × 10 6 − 21.6 × 10 6). Strep. mutans strain JC2, however, produced a fructan, 12.4 × 10 6, of the inulin-type with (1 → 2)-linked β-fructofuranoside residues and with some branching in the 6-position (6 per cent). All glucans isolated from Strep. mutans strains JC2, FA1 and Ingbritt and Strep. sanguis strain 903 were of the dextran-type, predominantly (1 → 6)-linked, or to a lesser extent (1 → 3)-linked (9–12 per cent) with branching in the 3- and 6-position (19–23 per cent). Both high (12.4 × 10 6) and low molecular weight glucans (129,000–136,000) were found.