Metabolite and Transcriptomic Differences of 2′-Fucosyllactose, 3-Fucosyllactose, and Difucosyllactose Assimilation by Bifidobacterium infantis Bi-26 and ATCC15697

The third most abundant solid in human milk is made up of unique, non-digestible, human milk oligosaccharides (HMOs) that provide an array of health benefits to the infant. They reach the colon intact and are fermented by the infant gut microbiota. HMOs can function as prebiotics for beneficial bacteria helping to shape the intestinal microbiota of breast-fed infants. Many infant formulas contain 2’Fucosyllactose (2’FL) to better mimic the health benefits observed from breast milk. However, research is needed to understand the mechanisms of recognition, uptake, and breakdown of individual monosaccharide moieties by bacteria. Research is also needed to determine if strains within the same species respond similarly to HMOs. To address these questions, we used a combination of metabolite testing and transcriptomics to compare gene transcription and metabolite secretion of Bifidobacterium longum subsp. infantis strain Bi-26 (Bi-26) and strain ATCC 15697 when grown on 2’-FL, 3-Fucosyllactose (3FL), and difucosyllactose (diFL) as the sole carbon source. Using transcriptomics we were able to identify 22 signature genes required for 2’FL, 3-FL, and diFL utilization. Additionally, we observed differences in growth between the two strains in the presence of glucose, lactose, diFL and 3FL. These growth differences led to the identification of unique gene signatures between the two strains and differences in metabolite secretion. These results indicate that not all strains within the same subspecies have the same response to HMOs. Comparisons between 2’FL, 3-FL, and diFL revealed similar growth, metabolite secretion, and transcription profiles for 2’-FL and 3-FL but not diFL. Both strains had significantly slower growth in the presence of diFL and induced additional pathways leading to secretion of different metabolites than 2’-FL or 3FL. These results provide valuable insight on the mode-of-action of 2’-FL, 3FL and diFL utilization by Bi-26 in the developing gut. All Funded through DuPont Nutrition and Biosciences.