In vitro utilization of mucin by Bacteroides fragilis

A method for isolating pig colon mucin in a soluble high-molecular-weight form, suitable for addition to bacterial growth media, is described. This preparation was utilized as a sole carbohydrate energy source by two strains of Bacteroides fragilis. The extent of degradation was compared with that of commercial pig gastric mucin by the same strains. Gas-liquid chromatographic analysis of the mucin carbohydrates and gel chromatography of the preparations were carried out before and after in vitro degradation. The mucin carbohydrates were utilized only to a very limited extent, colon mucin being more resistant to degradation than gastric mucin. Both mucins chromatographed at or near the excluded volume on Sepharose 4B, and only in the case of ATCC 25285 grown on gastric mucin was a significant degradation peak detected. If mucins are degraded in vivo by the sequential action of several bacteria, a pure culture in vitro might be expected to degrade mucins to a limited extent only. Techniques previously used to examine mucin utilization by pure cultures may have overlooked limited mucin degradation demonstrated by the methods used in this work.