Correlation between cell-adherent activity and surface structure in Porphyromonas gingivalis

The cell-adherent ability of 6 strains of Porphyromonas gingivalis (381, ATCC 33277, SU63, KD1, W50 and W83) was compared by using radiolabeled bacterial cells and human gingival fibroblasts (Gin 1), human periodontal ligament fibroblasts (HPLF) and human epithelial cells (Ca9-22) that had been grown on collagen beads. The cell-adherent activity of these organisms varied among strains; P. gingivalis strains 381, ATCC 33277 and SU63 bound to the target cells at a range of 14% to 72%, but the other 3 strains (KD1, W50 and W83) were scarcely bound (0.6% to 3.5%). On the other hand, whole bacterial cells and culture supernatants of all strains showed distinct hemagglutinating activity. The 3 strains showing high cell-adherent activity were hydrophobic and the other strains showing less activity were relatively hydrophilic. Furthermore, a number of peritrichous fimbriae were found on the surface of P. gingivalis strains 381, ATCC 33277 and SU63, which showed high adherent activity, whereas, fimbriae on the other 3 strains showing low adherent ability were barely apparent. Therefore, it was assumed that the cell-adherent activity of P. gingivalis was related to the hydrophobicity of the cell surface, which was related to the number of fimbriae.