The colonic mucus gel layer is composed of mucins that may be sulphated or sialyated. Sulphated mucins predominate in health while in ulcerative colitis (UC) sulphation is reduced. These differences result directly from inflammatory events. It may also be hypothesized that they arise in part from alterations in the colonic microbiota, particularly changes in the burden of sulphated mucin‐metabolizing species, such as Desulfovibrio (DSV) bacteria. The aim of this study was to correlate colonic mucin chemotypes and inflammatory scores in health and UC and relate these changes to changes in the colonization of colonic crypts by DSV.

Paired colonic biopsies from 34 healthy controls (HC) and 19 patients with active UC were collected for the purpose of parallel histological and microbiological assessment. High‐iron diamine and Alcian blue staining and haematoxylin and eosin of mucosal biopsy specimens were used to assess histological changes within the clinical spectrum of UC. Quantitative real‐time polymerase chain reaction analysis was employed to determine the total and DSV copy number within the colonic crypts.

Compared with HC, the mucin chemotype in UC was less sulphated and inversely correlated with the degree of mucosal inflammation. A weak but significant negative correlation was found between the abundance of sulphated mucins and DSV burden.

Mucin composition strongly correlates with the degree of mucosal inflammation, and to a lesser extent with DSV burden. These data suggest that mucin chemotype and DSV burden are linked phenomena and highlight the need to consider changes in mucin chemotype in the setting of microbial dysbiosis occurring within the colitic colon.