Researchers discover structure of Type V pili, which plays a role in gum disease

Researchers from the Molecular Cryo-Electron Microscopy Unit at the Okinawa Institute of Science and Technology (OIST) have discovered the structure of adhesive pili which attaches bacterial cells to the host, and the role they play in gum disease. In Japan, more than 75 percent of adults over the age of 35 have gum disease, which is caused primarily by the bacterial pathogen Porphyromonas gingivalis.

These pili create biofilms that cause serious problems, like gum erosion and tooth loss.

Research by OIST, with Professor Koji Nakayama at Nagasaki University and Professor Katsumi Imada at Osaka University, has been published in “Nature Microbiology.”

"Pili are vital for both the survival of the bacteria, and the creation of the biofilms," said Dr. Satoshi Shibata, first author and staff scientist in OIST's Unit, which is led by Associate Professor Matthias Wolf. "By taking a close look at these pili, our research has provided insights into how we can prevent biofilms from forming."

Within the class Bacteroidia, of which P. gingivalis is also a member, the bacteria have unique Type V pili, which are also found in bacteria that reside in the major colon.

This research has revealed that pili are constructed of protein units called pilins. The pilins in P. gingivalis are mostly FimA pilins.

To explore the structure of these pilins, Professor Imada and students from Osaka University crystalized them, and used a technique called X-ray crystallography to look at the pilins in their unassembled state, at the atomic level. Next, they looked at a fully assembled pili through electron microscopes, using a genetically engineered version of FimA pilins. From their images they then created a 3D atomic model of the assembled pilus structure.

This research could be helpful in creating new anti-bacterial drugs for diseases caused by any bacteria containing Type V pili.

"We're now trying to create an inhibitor that prevents pili from assembling," said Dr. Shibata. "This structure serves as a target to create new drugs, which are desperately needed to counter increasing antibiotic resistance. Finding novel antimicrobial compounds is a critical advantage in fighting these pathogens."