Bifidobacterium adolescentis

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 (,^{[1]Metformin alters the gut microbiome of individuals with treatment-naive type 2 diabetes, contributing to the therapeutic effects of the drugHao Wu, Eduardo Esteve, Valentina Tremaroli et al. · 2017Open reference 1 ↓} randomized controlled trial).

Mendelian randomization studies have identified genetically predicted B. adolescentis abundance as inversely associated with autoimmune disease risk (,^{[2]Xu 2022 — Causal relationship between gut microbiota and autoimmune diseases (SLE, RA, IBD, MS, T1D, CeD): two-sample Mendelian randomizationQian Xu, Jing-Jing Ni, Bai-Xue Han et al. · 2022Open reference 2 ↓} 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 (,^{[3]Multiple Sclerosis: A Story of the Interaction Between Gut Microbiome and Components of the Immune SystemEsraa Mohsen, Hesham Haffez, Sandra Ahmed et al. · 2025Open reference 3 ↓} review).