Bifidobacterium adolescentis is a Gram-positive, obligate anaerobic species within the phylum Actinobacteria and the dominant Bifidobacterium species in the adult human gut. It is a specialist degrader of resistant starch and dietary fiber, producing acetate and lactate that are cross-fed to butyrate-producing bacteria in the colon.
This species is consistently depleted in multiple disease states. In type 2 diabetes, metformin treatment has been shown to partially restore B. adolescentis abundance, suggesting the species is sensitive to the metabolic environment and may mediate some of metformin's gut-level therapeutic effects (wu 2017 metformin gut microbiome t2d nature medicine, randomized controlled trial). Mendelian randomization studies have identified genetically predicted B. adolescentis abundance as inversely associated with autoimmune disease risk (xu 2022 gut microbiota autoimmune diseases mendelian randomization, Mendelian randomization). The species is also depleted in multiple sclerosis, where its loss contributes to reduced short-chain fatty acid production and impaired immune regulation (mohsen 2025 ms gut microbiome immune interaction, review).
Cross-References
- actinobacteria — parent phylum
- akkermansia muciniphila — co-depleted commensal in multiple conditions
- type 2 diabetes — primary condition of depletion
- short chain fatty acids — metabolic output