Lineage variability in surface components expression within Porphyromonas gingivalis

The periodontopathogen Porphyromonas gingivalis is represented by a spectrum of phenotypes ranging from commensals to pathogenic lineages. Capsule and fimbriae are considered key virulence factors in this specie, involved in colonization and host defenses evasion. Since these virulence traits may not be expressed by certain strains, we aimed to test the hypothesis that certain clusters or genotypes of P. gingivalis correlate with the production of capsule and fimbriae. Sixteen P. gingivalis isolates were evaluated. Capsule (K) was detected by optical microscopy of negatively stained cells. The presence of fimbriae (F) was determined by TEM. Genotypes were determined by NotI macrorestriction fragments analysis through Pulsed-Field Gel Electrophoresis (PFGE) and Multi-locus sequence typing (MLST) based on seven house-keeping genes. The phenotypes included F(+)K(+) (n = 4), F(-)K(+) (n = 5), F(+)K(-) (n = 5) and F(-)K(-) (n = 2). The analysis of whole genome macrorestriction fragments revealed 14 different clusters. MLST data also revealed extensive genetic diversity; however, PFGE and MLST profiles showed evident differences. There was no association between P. gingivalis clusters and encapsulated and/or fimbriated phenotypes. Genotyping methods were not able to discriminate isolates according to the production of virulence factors such as capsule and major fimbriae, indicating that recombination played a key role in the expression of capsule and fimbriae in P. gingivalis.