Bifidobacterium adolescentis - a beneficial microbe.

Bifidobacterium adolescentis is one of the most abundant bifidobacterial species in the human large intestine, and is prevalent in 60-80% of healthy human adults with cell densities ranging from 109-1010 cells/g of faeces. Lower abundance is found in children and in elderly individuals. The species is evolutionary adapted to fermenting plant-derived glycans and is equipped with an extensive sugar transporter and degradation enzymes repertoire. Consequently, the species is strongly affected by dietary carbohydrates and is able to utilize a wide range of prebiotic molecules. B. adolescentis is specialized in metabolizing resistant starch and is considered a primary starch degrader enabling growth of other beneficial bacteria by cross-feeding. The major metabolic output is acetate and lactate in a ratio of 3:2. Several health-beneficial properties have been demonstrated in certain strains of B. adolescentis in vitro and in rodent models, including enhancement of the intestinal barrier function, anti-inflammatory and immune-regulatory effects, and the production of neurotransmitters (GABA), and vitamins. Although causalities have not been established, reduced abundance of B. adolescentis as part of a dysbiotic colonic microbiota in human observational studies has been associated with inflammatory bowel diseases, irritable bowel syndrome, coeliac disease, cystic fibrosis, Helicobacter pylori infection, type 1 and 2 diabetes, metabolic syndrome, nonalcoholic steatohepatitis, and certain allergies. It is therefore reasonable to conceive B. adolescentis as a health-associated, or even health-promoting bacterial species in humans.