The dynamics of Bifidobacterium species in utilizing human milk oligosaccharides
in the breastfed infant gut
2The Rachel and Selim Benin School of Computer Science and Engineering, The Hebrew University of Jerusalem, Israel
The human gut microbiome colonizes, stabilizes, and matures during the first few years of life, impacted considerably by infant food source (breast milk vs. infant formula). Breast milk contains human milk oligosaccharides (HMOs) which infants are unable to digest, supporting high abundance of bacteria capable of utilizing HMOs in the infant gut, such as Bifidobacterium.
Here we have established a longitudinal cohort, consisting of 22 infants with 110 samples of infant stool. The large majority of these samples contain a high percentage of Bifidobacterium (25-100%) and are classified based on their dominant Bifidobacterium species. We found mutualistic dynamics of some Bifidobacterium species while others were mutually exclusive.
To further investigate the dynamics of Bifidobacterium species in the infant gut we isolated several Bifidobacterium strains from our samples. Bifidobacterium longum subsp. infantis (B. infantis) showed significant intra-species differences in its ability to utilize sialylated HMOs compared to the type strain (ATCC 15697). In addition, we found differences in presence of HMO utilizing genes within the strains which may be able to explain this phenotype.
Competition assay between isolated Bifidobacterium breve (B. breve) and B. infantis on a variety of carbon sources revealed that although B. breve can not utilize most sialylated and fucosylated HMOs, when inoculated together with B. infantis a high abundance of B. breve is noted.
Our research sheds light on the interactions between multiple Bifidobacterium species in the infant gut, and further emphasizes the variation between wild and type strains and the infant-to-infant variation in Bifidobacterium functionality.