SUCROSE-DEPENDENT ACCUMULATION OF ORAL STREPTOCOCCI AND THEIR ADHESION-DEFECTIVE MUTANTS ON SALIVA-COATED HYDROXYAPATITE

The adhesion and accumulation of oral streptococci on saliva-coated hy droxyapatite was examined in strains representing species that appear in initial plaque (Streptococcus sanguise FC1 and Streptococcus oralis C5) and in more mature plaque (Streptococcus gordonii G9B). Washed ce lls of strains FC1 and C5 did not attach better to saliva-coated hydro xyapatite than did strain G9B, suggesting that the degree of initial a dhesiveness does not alone account for the temporal appearance of thes e bacteria in dental plaque. Growing cells of each strain were also ex amined for their ability to accumulate on saliva-coated hydroxyapatite . The addition of sucrose to the medium promoted the accumulation of s train G9B more than it promoted the accumulation of strains FC1 and C5 . Sucrose also enhanced the accumulation of adhesion-defective mutants of each strain to levels similar to those of the respective parent st rains. These results suggest that sucrose-dependent accumulation may f acilitate the colonization of the tooth surface by these species of or al streptococci when adhesion is limited by reduced bacterial adhesive ness or limited pellicle-binding sites.