title: UniFrac--an online tool for comparing microbial community diversity in a phylogenetic context.
abstract: BACKGROUND
  Moving beyond pairwise significance tests to compare many microbial communities simultaneously is critical for understanding large-scale trends in microbial ecology and community assembly. Techniques that allow microbial communities to be compared in a phylogenetic context are rapidly gaining acceptance, but the widespread application of these techniques has been hindered by the difficulty of performing the analyses.
  
  
  RESULTS
  We introduce UniFrac, a web application available at http://bmf.colorado.edu/unifrac, that allows several phylogenetic tests for differences among communities to be easily applied and interpreted. We demonstrate the use of UniFrac to cluster multiple environments, and to test which environments are significantly different. We show that analysis of previously published sequences from the Columbia river, its estuary, and the adjacent coastal ocean using the UniFrac interface provided insights that were not apparent from the initial data analysis, which used other commonly employed techniques to compare the communities.
  
  
  CONCLUSIONS
  UniFrac provides easy access to powerful multivariate techniques for comparing microbial communities in a phylogenetic context. We thus expect that it will provide a completely new picture of many microbial interactions and processes in both environmental and medical contexts.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA. lozupone@colorado.edu
authors.forename: Catherine
authors.initials: C
authors.lastname: Lozupone
authors.forename: Micah
authors.initials: M
authors.lastname: Hamady
authors.forename: Rob
authors.initials: R
authors.lastname: Knight
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics*; D016000:Cluster Analysis; D019295:Computational Biology / Q000379:methods*; D017753:Ecosystem; D004783:Environmental Microbiology; D014644:Genetic Variation; D020407:Internet; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D012336:RNA, Ribosomal, 16S