A new species of bacteria has been discovered in human mouth. Scientists feel that this discovery can help them to comprehend tooth decay and gum disease and to device a better treatment for it. Human mouth is the dwelling place for wide varieties of microbes such as viruses, fungi, protozoa and bacteria. They studied healthy tissue as well as the tumors in the mouth found three strains of bacteria called Prevotella that could not be identified. They are associated with various oral diseases and infections in other parts of the human body. Their name means inhabitant of tissue.