A new UCLA-led study provides clear evidence that cellular messengers in saliva may be able to regulate the growth of oral bacteria responsible for diseases, such as periodontitis and meningitis.
The study—which is published in the Journal for Dental Research—suggests that a body’s RNA (the cellular messengers) play an important role in managing the amount of good and bad bacteria in the mouth.
RNA acts as a messenger that transports DNA’s instructions to other parts of the cell. Small regulatory noncoding RNAs, known as sRNAs, regulate our genes. A new class of sRNAs has also been discovered called tsRNA, which is transfer RNA-derived small RNA.
The researchers began by analysing salivary sRNAs and found many of them belong to tsRNA with their sequences matching the partial transfer RNA sequences of several Gram-negative oral bacteria—bacteria that have a highly toxic outer layer that can cause periodontal disease.
These salivary tsRNAs could potentially affect bacterial tRNA, a type of RNA molecule that helps decode a messenger RNA sequence into a protein and is required for bacterial growth.
The Gram-negative bacterium used in the study to test this hypothesis was Fusobacterium nucleatum (F. nucleatum), the bacteria responsible for periodontitis.
The team showed that host cells respond to the presence of F. nucleatum by releasing specific tsRNA with sequence matching to tRNA of F. nucleatum. Furthermore, these released tsRNAs can inhibit the growth of F. nucleatum—but they have no effect on the growth of gram-positive oral bacteria, such as Streptococcus mitis, a bacterium that responds to antibiotics.
“This study establishes that there is a clear channel of communication between RNA messengers and bacteria in our mouth,” study co-author Professor David Wong said. “Furthermore, we have shown that these messengers may play an important role in mediating interactions between bacteria and their host.”
Another significant study finding was the majority of tRNA bacteria sequences that show high sequence similarity with salivary tsRNAs came from antibiotic-resistant Gram-negative bacteria.
This observation could lead to a better understanding of the mechanisms behind the growth of oral bacteria, resistance to antibiotics and, in turn, oral diseases, Wong said.