Molecular analysis of the developmental mechanism of periodontal and oral diseases by the genome analysis of oral biofilm.

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Dental plaque has the properties of a biofilm, similar to other biofilms found in the body and the environment. Modern molecular biological techniques have identified about 1000 different bacterial species in the dental biofilm, twice as many as can be cultured. Oral biofilms are very heterogeneous in structure. However, the relationship between the genomic information and the development of oral and periodontal diseases are still ambiguous. In this study, we focused on two theme, (1) Analysis of genomic variation of oral streptococci (2) Pathogenic mechanism of Porphyromonas gingivalis against oral epithelial cells.(1) Analysis of genomic variation of oral streptococciS. mutans strains have been classified into four serotypes (c, e, f, and k). However, little is known about the S. mutans population, including the clonal relationships among strains of S. mutans. We have developed a multilocus sequence typing (MLST) scheme for S. mutans. Eight housekeeping gene fragments were sequenced … More from each of 102 S. mutans isolates. We identified 92 sequence types in these 102 isolates, indicating that S. mutans contains a diverse population. No geographic specificity was identified. However, the distribution of the collagen-binding protein gene (cnm) and direct evidence of mother-to-child transmission were clearly evident. We also performed the whole genome sequencing of the S. mutans NN2025 strain, and its genome had an extensive genomic arrangement across the replicore.(2) Pathogenic mechanism of Porphyromonas gingivalis against oral epithelial cells.Porphyromonas gingivalis is a periodontal pathogen whose fimbriae are classified into six genotypes based on the diversity of the fimA genes encoding each fimbria subunit. It was suggested that P. gingivalis strains with type II fimbriae were more virulent than type I strains. The substitution of type I fimA with type II enhanced bacterial adhesion/invasion to epithelial cells, whereas substitution with type I fimA resulted in diminished efficiency. These results suggest that type II fimbriae are a critical determinant of P. gingivalis virulence. Less