Lysine gingipain (kgp) biovars of Porphyromonas gingivalis exhibit differential distribution on oral mucosal sites

The profile of Porphyromonas gingivalis kgp biotype and fimA genotype mosaic in subgingival plaque samples

Combined analysis of allelic variation of the virulence-associated, strain-specific lys-gingipain gene (kgp) and major fimbrial gene (fimA) of Porphyromonas gingivalis was undertaken in 116 subgingival plaque samples to understand the kgp biotype and fimA genotype profile in a subject-specific manner. Allelic variation in the polyadhesin domain of kgp from P. gingivalis strains 381 (ATCC 33277), HG66 and W83 generated four isoforms corresponding to four biotypes of P. gingivalis. Similarly, variation in the fimA subunit of the fimA gene cluster of P. gingivalis resulted in six fimA genotypes. Strain-specific differential PCR was performed for kgp and fimA using DNA isolated from subgingival plaque samples. Our findings demonstrate that all of the P. gingivalis kgp biotypes detected in this study were predominantly associated with the fimA II genotype. Dominance of kgp biotypes 381 or HG66 combined with fimA II fimbriae could imply an adaptive strategy by P. gingivalis to generate the fittest strains for survival in the host environment.

Genetic diversity in the oral pathogen Porphyromonas gingivalis: molecular mechanisms and biological consequences

Porphyromonas gingivalis is a Gram-negative anaerobic bacterium that colonizes the human oral cavity. It is implicated in the development of periodontitis, a chronic periodontal disease affecting half of the adult population in the USA. To survive in the oral cavity, these bacteria must colonize dental plaque biofilms in competition with other bacterial species. Long-term survival requires P. gingivalis to evade host immune responses, while simultaneously adapting to the changing physiology of the host and to alterations in the plaque biofilm. In reflection of this highly variable niche, P. gingivalis is a genetically diverse species and in this review the authors summarize genetic diversity as it relates to pathogenicity in P. gingivalis. Recent studies revealing a variety of mechanisms by which adaptive changes in genetic content can occur are also reviewed. Understanding the genetic plasticity of P. gingivalis will provide a better framework for understanding the host-microbe interactions associated with periodontal disease.