The structure of carbohydrates determines competition among bacteria and the production of fatty acids essential for protecting the human epithelium and metabolism, the website infohub.kz reports.
Scientists have synthesized biochemical and microbiological data to determine how the spatial structure and chemical complexity of dietary fibers influence bacterial communities in the human colon. The results of the scientific review were published in the journal Proceedings of the Nutrition Society. Fiber was previously often viewed as a uniform mass, but new data show that it is its molecular diversity that triggers food cooperation and competition among microorganisms.
In the colon, bacteria ferment undigested carbohydrates, producing short-chain fatty acids — acetate, propionate and butyrate. These substances regulate the body's energy metabolism and curb systemic inflammation, while butyrate serves as the main nutrient source for the cells lining the colon. The availability of plant fibers to bacterial enzymes depends on their nature: from insoluble microfibrils of crystalline cellulose to pectins and various types of resistant starch.
The researchers found that microorganisms use fundamentally different strategies to break down complex polymers. Bacteria of the genus Bacteroides have more than a hundred polysaccharide utilization loci (PUL), recognizing a wide range of carbohydrates. At the same time, bacteria of the phylum Firmicutes rely on highly specialized complexes. For example, the species Ruminococcus champanellensis uses surface multienzyme cellulosomes to bind and hydrolyze crystalline cellulose.
The species Ruminococcus bromii acts as a key degrader of resistant starch through amylosomes. During fermentation, the bacterium breaks the substrate down into simple sugars — glucose and maltose — feeding its neighbors in the microbiota. Experiments showed that in people lacking this microbe, most of the starch is excreted undigested. Other bacterial species, including Coprococcus catus, convert the lactate byproduct into propionate and butyrate, protecting the environment from acidification. The scientists emphasize that understanding these food chains is essential for creating targeted prebiotics.