Colonic biogeography in health and ulcerative colitis.

The relevance of biogeography to the distal gut microbiota has been investigated in both health and inflammatory bowel disease (IBD), however multiple factors, including sample type and methodology, microbiota characterization and interpersonal variability make the construction of a core model of colonic biogeography challenging. In addition, how phylogenetic classification relates to immunogenicity and whether consistent alterations in the microbiota are associated with ulcerative colitis (UC) remain open questions. This addendum seeks to review the human colonic microbiota in health and UC as currently understood, in the broader context of the human microbiome.