A Major Fimbrilin Variant of Mfa1 Fimbriae in Porphyromonas gingivalis

Area of Science:

• Microbiology
• Oral Health
• Bacterial Pathogenesis

Background:

• Porphyromonas gingivalis, a key periodontal pathogen, possesses FimA and Mfa1 fimbriae.
• Previous observations noted fimbria-like structures in P. gingivalis strains lacking FimA or Mfa1.

Purpose of the Study:

• To identify the major protein component of previously observed fimbria-like structures in P. gingivalis.
• To characterize the genetic and functional relationship of this novel protein with known fimbrial systems.

Main Methods:

• Bacterial lysate protein analysis to identify the major component.
• DNA sequencing to determine the genetic locus of the novel protein.
• Amino acid homology and antigenicity comparisons.
• Gene knockout and complementation studies.

Main Results:

• A 53-kDa major outer membrane protein (53K protein) was identified as a major fimbrilin of a novel fimbria type.
• The gene encoding the 53K protein is located at the mfa1 locus but shows low homology and different antigenicity to Mfa1.
• The 53K protein was found in 41% of P. gingivalis strains, with no co-expression with Mfa1.
• Mutational analysis confirmed the role of the 53K protein in fimbrial structure.

Conclusions:

• The 53K protein represents a distinct major fimbrilin of Mfa1 fimbriae in P. gingivalis.
• This finding expands the known repertoire of fimbrial structures and their genetic basis in this important oral pathogen.