Phylogenetic architecture and abundance of OTUs with ≥97% similarity in five human subjects. The left axis is a neighbor-joining tree composed of representative sequences from each of the 113 OTUs identified in the subjects. Abundance of OTUs in each subject is indicated by a grayscale value in the heat plot to the right. Each column of the heat plot corresponds to each arm of the five subjects (L is left arm; R is right arm). The heat plot is color-coded according to the major bacterial divisions observed: Proteobacteria (red), Bacteroidetes (blue), Firmicutes (yellow), and Actinobacteria (green).