In VitroEffects of Mucin Fermentation on the Growth of Human Colonic Sulphate-Reducing Bacteria: ECOLOGY

Abstract Mucins are endogenously produced glycoproteins that are available for fermentation by populations of human colonic bacteria. As these substrates have a relatively high sulphate content, their metabolism can potentially release this anion in a free form. Dissimilatory sulphate-reducing bacteria may then further metabolise that sulphate released to produce sulphide, which is highly toxic. Studies showed that the batch culture incubation of mucin with faecal bacteria produced an increase in sulphide that was not apparent with other fermentable carbohydrates. Chemostat enrichment experiments showed that a variety of gut micro-organisms were able to ferment mucin, or products of its hydrolysis. However, pure cultures of gut anaerobes were only partly responsible, indicating that consortia of bacteria are required for the full metabolism of mucin. Bacteroides fragilis released sulphate from mucin, indicating sulphatase activity in the organism. Co-culture experiments with B. fragilis and Desulfovibrio desulfuricans showed that the former organism was able to release sulphate from mucin, in sufficient amounts to allow efficient growth of the sulphate-reducing bacterium, which then produced sulphides.