Bifidobacterium longum (B. longum)

Bifidobacterium longum is a Gram-positive, rod-shaped, non-spore-forming bacterium that is a primary commensal inhabitant of the human gastrointestinal tract, particularly dominant in breastfed infants (PMID: 28223713). It is widely utilized as a probiotic and live biotherapeutic agent due to its ability to ferment complex carbohydrates into short-chain fatty acids, which support gut health and inhibit pathogenic colonization (PMID: 29397456). While it is not a traditional molecular target like a receptor or enzyme, it is a therapeutic entity used to manage gastrointestinal disorders such as irritable bowel syndrome and diarrhea (PMID: 27126333). Research also highlights its role in the gut-brain axis, where it may alleviate symptoms of anxiety and depression through immunomodulatory and neuroactive pathways (PMID: 30248161). The organism is generally recognized as safe (GRAS), though its clinical use requires caution in vulnerable, immunocompromised populations to avoid rare systemic infections. Its therapeutic efficacy is typically monitored through changes in the gut microbiota composition and metabolic byproducts in the stool.

Other names

Bifidobacterium longum subsp. longumBifidobacterium longum subsp. infantisBifidobacterium longum subsp. suisBifidobacterium infantisActinomyces protoformis

Bifidobacterium longum exerts its effects by fermenting dietary polysaccharides into lactic and acetic acids, which lowers the intestinal pH and inhibits the growth of acid-sensitive pathogens (PMID: 29397456). It enhances the intestinal epithelial barrier by upregulating the expression of tight junction proteins such as occludin and zonula occludens-1, thereby reducing intestinal permeability (PMID: 30248161). Additionally, it modulates the host immune system by stimulating the production of anti-inflammatory cytokines like IL-10 and inducing the differentiation of regulatory T cells (PMID: 27126333). In the context of the gut-brain axis, it may influence neurotransmitter signaling and reduce systemic inflammation that contributes to mood disorders (PMID: 30248161).