According to research published in the August issue of the International Journal of Systematic and Evolutionary Microbiology, scientists have discovered a new species of bacteria in the human mouth. The finding could help scientists understand tooth decay and gum disease, which may lead to better treatments.

"The healthy human mouth is home to a tremendous variety of microbes including viruses, fungi, protozoa, and bacteria," said William Wade, professor at King’s College London Dental Institute. "The bacteria are the most numerous. There are 100 million in every milliliter of saliva and more than 600 different species in the mouth. Around half of these have yet to be named, and we are trying to describe and name the new species."

Scientists studied healthy tissue as well as tumors in the mouth and found three strains of bacteria called Prevotella that could not be identified. Prevotella species are part of the normal microbial flora in humans and are associated with various oral diseases and infections in other parts of the body. The researchers named the new species Prevotella histicola; “histicola” means inhabitant of tissue.

"Interestingly, this species was isolated from within the oral tissues, both in oral cancers and normal, healthy tissue," Wade said. "This confirms other work showing that oral bacteria can invade both tissues and individual cells."

Tooth decay and gum disease are caused by changes in the microbes normally present in the mouth. To understand these diseases better, scientists first need to know which bacteria are present in human mouths. Understanding the composition of the oral microbiota will also help scientists devise new prevention measures and treatments for oral diseases.