Novel Genes and Metabolite Trends in Bifidobacterium longum ssp. infantis Bi-26 Involved in Metabolism of Human Milk Oligosaccharide 2'-fucosyllactose

Human milk oligosaccharides (HMOs) function as prebiotics for beneficial bacteria in the developing gut, often dominated by Bifidobacterium spp. To understand the relationship between Bifidobacterium utilizing HMOs and how the metabolites that are produced could affect the host, we analyzed the metabolism of HMO 2'-fucosyllactose (2'-FL) in Bifidobacterium longum ssp. infantis Bi-26. RNA-seq and metabolite analysis (NMR/GCMS) was performed on samples at early (A600=0.25), mid-log (0.5-0.7) and late-log phases (1.0-2.0) of growth. Transcriptomic analysis revealed many gene clusters including three novel ABC-type sugar transport clusters to be upregulated in Bi-26 involved in processing of 2'-FL along with metabolism of its monomers glucose, fucose and galactose. Metabolite data confirmed the production of formate, acetate, 1,2-propanediol, lactate and cleaving of fucose from 2'-FL. The formation of acetate, formate, and lactate showed how the cell uses metabolites during fermentation to produce higher levels of ATP (mid-log compared to other stages) or generate cofactors to balance redox. We concluded 2'-FL metabolism is a complex process involving gene clusters throughout the genome producing more metabolites compared to lactose. These results provide valuable insight on the mode-of-action of 2'-FL utilization by Bifidobacterium longum ssp. infantis Bi-26. Overall design: Bifidobacterium longum subsp. infantis strain Bi-26 was used in this study with 2'-FL as the test carbon source and lactose as the control carbon source, Samples were done in duplicate with samples taken at early phase (A600 ~0.2) mid log (0.5-1.1) and late log (1.1+)