October 23, 2014

AUSTIN, Texas, USA: Studies on the human microbiome have shown that shifts in oral microbiota are associated with a number of diseases, including obesity, Crohn’s disease, diabetes and periodontitis. Now, U.S. scientists have found that oral bacteria act differently in diseased patients compared with healthy individuals. They believe that the findings could be used to develop methods to prevent or even reverse diseases such as periodontal disease. Although it is known that the composition of the microbiome changes during the transition from health to disease, it is still unclear how specific activities of different members of the microbial community affect diseases. In order to understand how different bacteria act in healthy and diseased individuals, researchers at the University of Texas at Austin examined periodontal plaque samples from ten patients from Izmir in Turkey with aggressive periodontitis. Using supercomputers, the researchers compared the expression of 160,000 genes in healthy and diseased periodontal communities and found that these communities show defined differences in metabolism. “In other words, a species of bacteria that ate one thing, such as fructose, can switch to a different kind of sugar to feed on if diseased,” explained Dr. Marvin Whiteley, professor of molecular biosciences at the university. A major question concerning the mechanism underlying the changes is whether changes in composition and behavior cause diseases or are a consequence of diseases. In this respect, the present study demonstrated that differential expression of metabolic genes was associated with the periodontal disease state. For instance, the expression of butyrate production genes by the bacterium Fusobacterium nucleatum increased during disease, suggesting that F. nucleatum butyrate production promotes periodontitis. However, further studies are needed to verify this hypothesis, the researchers said. Whiteley said that the research could help determine biomarkers that predict whether a patient is at risk of developing periodontitis. As bacterial populations can be manipulated, researchers might be able to shift them back to that of a healthy microbiome . The findings may thus also benefit periodontal treatment. According to the latest figures provided by the Centers for Disease Control and Prevention, about 47 percent of adults aged 30 and over in the U.S. have periodontitis. The organization estimates that over 8 percent of adults have severe periodontitis. The study, titled “Metatranscriptomics of the Human Oral Microbiome during Health and Disease,” was published in the April issue of mBio, an open-access journal published by the American Society for Microbiology.