Clustering of bacterial taxa by cognitive function. Weighted UniFrac was used to generate a matrix of pairwise distances between communities and a scatterplot was generated from the matrix of distances using Principal Coordinate Analysis in QIIME. Each symbol represents the values of all samples from one participant analyzed collectively. In the left hand panel all OTUs that occur more than 150 times are included in the analysis. In the middle panel, the OTU table is further edited to remove any OTUs assigned to the Fusobacteriaceae or Prevotellaceae. In the right hand panel, only OTUs that were identified as Fusobacteriaceae or Prevotellaceae were analyzed. (green circle) cognitively normal, (red square) cognitively impaired without dementia, and (purple triangle) dementia. OTU, Operational Taxonomic Units.