Periodontal disease is caused by bacteria and is one of the most prevalent diseases worldwide. Porphyromonas gingivalis (P. gingivalis). In Japan alone, approximately 80% of adults over the age of 30 are affected or considered to be at risk.
Published in communication biologyA joint study by Okinawa Institute of Science and Technology Graduate University (OIST), Tottori University, Hiroshima University, and Nagasaki University has provided new insights into how this bacterium causes plaque formation. The researchers used cryo-electron (cryo-EM) microscopy to reveal the 3D structure of Mfa pili, the arm-shaped filaments that allow bacteria to attach to host tissues and other microorganisms.
Lead author Dr. Satoshi Shibata, a former researcher at OIST’s Molecular Cryo-EM Unit and currently a lecturer at Tottori University, said: P. gingivalis By adhering to host tissues, establishing infection, and participating in biofilm formation, they can inform the development of future therapeutic strategies. Our detailed structural information could serve as a drug design template to identify compounds that block adhesion and infection. ”
how P. gingivalis form a plaque
To attach to the host or other microorganisms, P. gingivalis uses two different types of filaments (piles): Fim and Mfa. Both are made up of multiple protein subunits that combine to form long arm-like structures that can bind to different types of bacteria and human tissues. In Mfa, most of these subunits are Mfa1 proteins.
The authors have previously described the structure of FimA, a key component of Fim pili, and have long been interested in the structure and function of these filaments. In this new publication, they elucidate the structure of the Mfa1 chain, which is the core of Mfa pili, and explain how these assemble and bind to other bacteria, providing a more complete picture.
To understand filament formation, the researchers first polymerized the Mfa1 protein in vitro and analyzed it with cryo-EM to determine its structure at near-atomic resolution of 3.0 Å.
By modifying the protein, the research team investigated the role and importance of specific sites on filament assembly. They demonstrated how the Mfa protein binds in a process called strand exchange, relying on interactions within a specific region of the protein (the C-terminus) for structural stability.
Cryo-EM mapping revealed metal ions within the Mfa filament, which further analysis identified as calcium. “Our tests suggest that this calcium binding may help bacteria evade immune recognition,” Shibata emphasizes.
The researchers were also able to visualize the interactions of the Mfa filaments using computer simulations. Streptococcus gordoniicommonly associated with another bacterium P. gingivalis In the dental plaque. By determining how these bacteria interact, scientists may be able to more easily identify compounds that block these interactions and inhibit plaque formation.
In addition to periodontal disease, P. gingivalis It is thought to be involved in a wide range of diseases, including pneumonia, diabetes, Alzheimer’s disease, rheumatoid arthritis, stroke, cardiovascular disease, and adverse pregnancy outcomes. By providing detailed structural information, the researchers hope to help scientists develop treatments. P. gingivalis-Related diseases.
sauce:
Okinawa Institute of Science and Technology (OIST) Graduate School
Reference magazines:
Shinji Shibata others. (2026). Cryo-EM structure of naturally assembled Mfa type V fimbriae from the periodontal pathogen Porphyromonas gingivalis. Communication biology. DOI: 10.1038/s42003-026-10515-2. https://www.nature.com/articles/s42003-026-10515-2
