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Isolation and characterization of a minor fimbria from Porphyromonas gingivalis
1Department of Oral Biology, School of Dental Medicine, State University of New York at Buffalo, 14214, USA.
Abstract:
We have discovered two distinctly different fimbriae expressed by the same Porphyromonas gingivalis strain. The construction of a fimA mutant of P. gingivalis ATCC 33277 has previously been reported by N. Hamada et al. (Infect. Immun. 62:1696-1704, 1994). Expression of fimbriae on the surface of the fimA mutant and the wild-type strain, ATCC 33277, were investigated by electron microscopy. The wild-type strain produced long fimbrial structures extending from the cell surface, whereas those structures were not observed on the fimA mutant. However, short fimbrial structures were seen on the surface of the fimA mutant. The short fimbrial protein was purified from the fimA mutant by selective protein precipitation and chromatography on DEAE Sepharose CL-6B. We have found that the second fimbrial structure of P. gingivalis ATCC 33277 is distinct from the 41-kDa (43-kDa) major fimbrial protein (FimA). We provisionally call this protein minor fimbriae. The molecular mass of the minor fimbriae is 67 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions after boiling at 100 degrees C. The component shows a ladder-like pattern at 80 degrees C under nonreducing conditions, suggesting a tendency to aggregate or polymerize. In immunoblotting analysis, anti-minor fimbria serum reacted with both the 100 degrees C- and the 80 degrees C-treated minor fimbriae. The anti-minor fimbria serum also reacts with the same-molecular-size fimbrial preparation from the wild-type strain. Immunogold electron microscopy showed that the anti-minor fimbria serum bound to the minor fimbria on the cell surface of the wild-type strain. This is the first report on the identification of the minor fimbria produced by P. gingivalis. These results suggest that the minor fimbriae appearing on the fimA mutant strain are produced together with numerous long major fimbriae on the wild-type strain. Moreover, the minor fimbriae are different in size and antigenicity from the earlier-reported FimA, a major 41-kDa fimbrial component of P. gingivalis.
Insights
Porphyromonas gingivalis produces two distinct fimbriae. Researchers identified a novel minor fimbriae distinct from the major FimA protein, aiding in understanding P. gingivalis virulence factors.
Area of Science:
- Microbiology
- Bacteriology
- Molecular Biology
Background:
- Porphyromonas gingivalis is a key pathogen in periodontitis.
- Fimbriae are crucial virulence factors in many bacteria, including P. gingivalis.
- Previous research identified the major fimbrial protein (FimA) in P. gingivalis.
Purpose of the Study:
- To identify and characterize novel fimbrial structures in P. gingivalis.
- To differentiate newly discovered fimbriae from the known major FimA protein.
- To investigate the expression and properties of these fimbriae.
Main Methods:
- Electron microscopy to visualize fimbriae on wild-type and fimA mutant strains.
- Purification of the novel fimbrial protein using selective precipitation and chromatography.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to determine molecular mass.
- Immunoblotting and immunogold electron microscopy for serological analysis.
Main Results:
- P. gingivalis ATCC 33277 expresses two distinct fimbriae: long major fimbriae and short minor fimbriae.
- A fimA mutant strain lacked the long fimbriae but still produced short fimbrial structures.
- The purified minor fimbriae have an estimated molecular mass of 67 kDa and exhibit aggregation properties.
- Anti-minor fimbria serum cross-reacted with the wild-type strain, confirming its presence on the cell surface.
Conclusions:
- This study reports the first identification of minor fimbriae in P. gingivalis.
- Minor fimbriae are distinct from the major FimA protein in size and antigenicity.
- The presence of both major and minor fimbriae contributes to the surface characteristics of P. gingivalis.