In a new study published inmSystems, researchers led by Osaka University have revealed the role ofF. nucleatumin the development of periodontitis, also known as gum disease. Periodontitis is marked by inflammation of the gums and can lead to gum damage and tooth loss. One important microbe involved in periodontitis is a pathogen known asPorphyromonas gingivalis(P. gingivalis).

Within the oral microbiome, a process called metabolic cross-feeding occurs, wherein bacteria secrete products -- often as nutritional wastes -- that are consumed by other bacteria, thereby promoting the survival of those bacteria. The research group previously showed thatF. nucleatum, a common component of the oral microbiome in both healthy and disease states, participates in a cross-feeding relationship with another oral bacteria. However, the mechanisms underlying the involvement ofF. nucleatumin the progression of periodontitis had not yet been determined, prompting the research team to further examine the interactions ofF. nucleatumand other oral bacteria.

"To better understand how the metabolic interactions ofF. nucleatummay contribute to the development of gum disease, we analyzed co-cultures ofF. nucleatumwith other commensal bacteria found in the mouth," says lead author Akito Sakanaka. Commensals are microbes (including bacteria) that reside on the surface of the body and within the oral cavity and digestive tract without causing harm.

The researchers found that co-culture ofF. nucleatumwith other commensal bacteria resulted in an increase in the availability of certain amino acids thatF. nucleatumthen used to produce polyamines such as putrescine and cadaverine.

"We found thatF. nucleatum产生多胺如腐胺和尸体ine through metabolic cross-feeding with other commensal bacteria," says corresponding author Masae Kuboniwa, DDS, PhD. "These polyamines then create favorable conditions that allow the periodontal pathogenP. gingivalisto grow and spread, thus promoting the development of periodontitis."

Analysis of plaque samples from human subjects showed that the presence ofP. gingivaliscoincided with the presence of the genetic information required for the production of putrescine found withinF. nucleatumand other commensal bacteria. These findings suggest thatF. nucleatumintegrates a metabolic network within the oral microbiome which may promote the development of periodontal disease.

"In other words, neglect of toothbrushing may provide ample cross-feeding opportunities where oral bacteria spontaneously start exchanging metabolites viaF. nucleatum, ultimately leading to an increase in periodontal pathogens." says senior author Atsuo Amano, DDS, PhD. "Considering thatF. nucleatumis also strongly linked to serious systemic conditions such as colorectal cancer, more work is needed to focus the metabolic properties ofF. nucleatumwithin polymicrobial communities, which might open new therapeutic opportunities forF. nucleatum-mediated diseases."

It is not clear why polyamines induce drastic changes in behaviors ofP. gingivalis. Far more work is needed to uncover the molecular mechanisms underlying the consequences of polyamines on the physiology ofP. gingivalis.