We and other scientists discovered that gut bacteria contribute to the development of type 1 diabetes. The varieties of gut bacteria in diabetic children and those at high risk of developing diabetes are very different from those of healthy individuals. Using an animal model of type 1 diabetes, we recently found that some of the gut bacteria share similar molecular markers with insulin-producing beta cells in pancreas. The presence of these bacteria can stimulate the autoreactive T cells to mistakenly attack insulin-producing beta cells. One group of these diabetes-inducing bacteria is called Fusobacteria. We found more Fusobacteria in diabetic mice and the number of Fusobacteria increased as mice approached onset of diabetes. We hypothesize that Fusobacteria are associated with human type 1 diabetes. If our hypothesis is correct, we may be able to use the quantity of Fusobacteria present in the gut to predict and monitor the time of diabetes development in individuals who are prone to the disease.