Short Fimbriae of Porphyromonas gingivalis and Their Role in Coadhesion with Streptococcus gordonii

Abstract

Porphyromonas gingivalis, one of the causative agents of adult periodontitis, attaches and forms biofilms on substrata of Streptococcus gordonii. Coadhesion and biofilm development between these organisms requires the interaction of the short fimbriae of P. gingivalis with the SspB streptococcal surface polypeptide. In this study we investigated the structure and binding activities of the short fimbriae of P. gingivalis. Electron microscopy showed that isolated short fimbriae have an average length of 103 nm and exhibit a helical structure with a pitch of ca. 27 nm. Mfa1, the major protein subunit of the short fimbriae, bound to SspB protein, and this reaction was inhibited by purified recombinant Mfa1 and monospecifc anti-Mfa1 serum in a dose-dependent manner. Complementation of a polar Mfa1 mutant with the mfa1 gene restored the coadhesion phenotype of P. gingivalis. Hence, the Mfa1 structural fimbrial subunit does not require accessory proteins for binding to SspB. Furthermore, the interaction of Mfa1 with SspB is necessary for optimal coadhesion between P. gingivalis and S. gordonii.

Adaptation of Porphyromonas gingivalis to microaerophilic conditions involves increased consumption of formate and reduced utilization of lactate

“…However, it does possess the mfa locus (PG0178), encoding a 67 kDa fimbrillin forming short fimbria. This locus has been shown to play a role in adherence to other organisms such as Streptococcus gordonii; however, it also inhibits invasion of host cells (Capestany et al, 2008;Park et al, 2005). It is noteworthy that this locus was upregulated under aerobic conditions (1.4-fold, results not shown), which indicates that it plays a role during the early colonization stages when the organism may be present in the supragingival environment.…”

Involvement of minor components associated with the FimA fimbriae of Porphyromonas gingivalis in adhesive functions

“…Both types of fimbriae appear to be abundant in some strains and represent evolutionarily unique groups, since no homologues of FimA or Mfa1 have been found in any other bacteria. The FimA fimbriae are approximately 0.3-1.6 mm in length and 5 nm in diameter (Yoshimura et al, 1984), whereas the Mfa1 (75 kDa) fimbriae are slightly thicker (3.5-6.5 nm in width) and considerably shorter (80-120 nm in length) than the FimA fimbriae (Park et al, 2005).…”

Porphyromonas gingivalis Minor Fimbriae Are Required for Cell-Cell Interactions

“…The evident autoaggregation of FAT may result from low expression of the major fimbriae, which exposes the shorter minor fimbriae. Autoaggregation was restored in a complemented ⌬mfa1 strain (SMFC) carrying plasmid pT-MFA containing a 2.5-kb fragment of the upstream and coding region of the mfa1 gene (15), suggesting that this phenotype did not result from polar effects. These data demonstrate that the degree of P. gingivalis aggregation correlated with the expression levels of mfa1 and fimA.…”

“…The subunit of the major fimbriae is a 41-kDa protein (FimA, fimbrillin) and is encoded by the fimA gene (2). A thin, short secondary fimbrial structure, termed minor fimbriae or short fimbriae (15), is composed of a 67-kDa protein encoded by the mfa1 gene (4). Both major and minor fimbriae appear to contribute to the pathogenicity of P. gingivalis (1).…”