Surface structures, co-aggregation and adherence phenomena of Streptococcus oralis and related species.

Seven strains of Streptococcus oralis were found to possess surface structures. Four strains possessed long fimbriae which ranged in length from 266-366 nm, while the remaining three strains possessed shorter peritrichously distributed fibrils which ranged in length from 80-197 nm. The fibrillar strains were morphologically similar to strains of Streptococcus sanguis I and II and Streptococcus mitis. No strain of S. oralis produced tufts of fibrils like certain strains of S. sanguis I. Strains of Streptococcus milleri produced peritrichously distributed fimbriae which were morphologically dissimilar to the fimbriae produced by S. oralis strains. S. oralis strains were moderately to highly hydrophobic, but hydrophobicity could not be related to adhesion parameters or type or length or density of surface structures. Furthermore, there appeared to be no correlation between type of surface structures and adhesion parameters. Two of the three fibrillar strains of S. oralis and the peritrichously fibrillar strains of S. sanguis, together with one strain of S. milleri, were able to co-aggregate with actinomycetes.