ERP012576 PRJEB11223 ena-STUDY-STANFORD MEDICAL SCHOOL-05-10-2015-03:21:53:049-137 Survey of 16S rRNA genes for microbes inhabiting the smooth surface of teeth We studied the spatial and temporal variation of the bacterial communities inhabiting the smooth surfaces of teeth in humans. We sought to determine whether community composition and structure varies between and across teeth and tooth aspects over the course of one week. To address these questions, we collected and analyzed one of the largest oral datasets amassed to date (N=1 922). We analyzed samples taken from the buccal and lingual aspects of the molars and incisors in each of 11 individuals as well as samples of all teeth in a subset of 4 subjects. Our findings demonstrate that bacterial communities are not subject to directional selection over the course of 1 week. While inter-individual variation explained most of the observed variation, our results suggest that the molars and incisors represent opposing poles of an ecological gradient with the remaining tooth classes arrayed in a structured fashion in between. Across the observed gradient, 12 taxa were found to vary significantly as a function of the physical distance separating sites. Finally, we show that a model of the mouth that incorporated geographic covariates explains more of the variation in microbial community structure than can categorical variables, such as tooth or tooth class, alone. Taken together, these findings suggest significant habitat differentiation between and across teeth in the human mouth. We speculate that these patterns are driven by variation in the proximity of sites to the major salivary glands, and we are currently exploring this hypothesis using an experimental model of hyposalivation. Biogeography of Supragingival Plaque We studied the spatial and temporal variation of the bacterial communities inhabiting the smooth surfaces of teeth in humans. We sought to determine whether community composition and structure varies between and across teeth and tooth aspects over the course of one week. To address these questions, we collected and analyzed one of the largest oral datasets amassed to date (N=1 922). We analyzed samples taken from the buccal and lingual aspects of the molars and incisors in each of 11 individuals as well as samples of all teeth in a subset of 4 subjects. Our findings demonstrate that bacterial communities are not subject to directional selection over the course of 1 week. While inter-individual variation explained most of the observed variation, our results suggest that the molars and incisors represent opposing poles of an ecological gradient with the remaining tooth classes arrayed in a structured fashion in between. Across the observed gradient, 12 taxa were found to vary significantly as a function of the physical distance separating sites. Finally, we show that a model of the mouth that incorporated geographic covariates explains more of the variation in microbial community structure than can categorical variables, such as tooth or tooth class, alone. Taken together, these findings suggest significant habitat differentiation between and across teeth in the human mouth. We speculate that these patterns are driven by variation in the proximity of sites to the major salivary glands, and we are currently exploring this hypothesis using an experimental model of hyposalivation. 16S