Surface properties and ultrastructure of Porphyromonas gingivalis W50 and pleiotropic mutants

Abstract

– Cell surface ultrastructure and other surface properties of Porphyromonas gingivalis strain W50 and pleiotropic mutants W50/BP1 (black), W50/BR1 (brown), and W50/BE1 (beige) were studied. The percentage hydrophobicity of strains W50, W50/BP1, W50/BR1, and W50/ BE1 gradually decreased from 24 to 9. Ruthenium red stained cells studied by transmission electron microscopy revealed a layer of extracellular polymeric material of varying thickness depending on the strain. The layer was thickest in W50/BP1 (15–20 nm), strains W50 and W50/ BR1 both had a layer of 12–15 nm, while strain W50/BE1 completely lacked this layer. The results clearly showed that the hydrophobicity of P. gingivalis was related not only to the thickness of the layer but also to other factors like the composition of the capsular material, such that only strain W50/BE1, for example, showed no haemagglutinating activity. The surface properties of the pleiotropic mutants appeared to be stable characteristics as cells grown on either solid or in liquid media gave comparable results. The loss of virulence of the beige strain (W50/BE1) is probably partly due to the alteration of these surface properties. Both virulent and avirulent strains, however, possessed extracellular vesicles.

Inhibition of Actinomyces viscosus – Porphyromonas gingivalis coadhesion by trypsin and other proteins

“…In substituting the use of chemically induced trypact" mutants, there is a risk that the strains might also be deficient in other adhesion-related defects. Our finding that they were less able than most P. gingivalis strains to coat hexadecatie droplets and previous reports that pleiotropic mutants were protease-deficient, less hydrophobic, and weak hemagglutinators (14,29) caution against strong conclusions based solely on the use of such mutants. However, from our experiments it seems unlikely that the inability of the two trypact" mutants to coaggregate with A. viseosus derived exclusively from their inability to degrade trypsin-sensitive substrates on the A. viscosus surface and thereby "prime" pre-viously cryptic receptors for coadhesion.…”

Phagocytosis and virulence of different strains of Porphyromonas gingivalis

“…It has been suggested that the degree of encapsulation and resistance to phagocytosis are factors which may influence the ability of strains to be invasive in induced infections (20)(21)(22). Of the nine poorly phagocytosed strains which possessed a glyeocalyx-like structure, only two were capable of producing an invasive lesion when injected subcutaneously.…”

“…However, recent results indicate that the protease and collagenolytic activities do not account for the diflferences between the invasive and non-invasive strains (18,19). It has also been suggested that differences in virulence might be due to the degree of encapsulation and resistance to phagocytosis (20)(21)(22).…”

Pathogenicity and virulence of black-pigmented Gram-negative anaerobes

“…There are also P. gingivalis strains with only a marginal electron dense layer of 15-25 nm attached to the cell surface. The degree of capsulation and resistance to phagocytosis are factors that may influence the invasiveness of strains in experimental infections [52,[98][99][100], but a clear correlation between the presence of glycocalyces on P. gingivalis strains and virulence of the bacteria in the mouse pathogenicity model has not been established [94]. The exact role of the glycocalyx for the pathogenicity of P. gingivalis is not yet clear.…”