Strain-specific strategies of 2′-fucosyllactose, 3-fucosyllactose, and difucosyllactose assimilation by Bifidobacterium longum subsp. infantis Bi-26 and ATCC 15697

Abstract

Human milk provides essential nutrients for infant nutrition. A large proportion of human milk is composed of human milk oligosaccharides (HMOs), which are resistant to digestion by the infant. Instead, HMOs act as a bioactive and prebiotic enriching HMO-utilizing bacteria and cause systematic changes in the host. Several species of Bifidobacterium have been shown to utilize HMOs by conserved, as well as species-specific pathways, but less work has been done to study variation within species or sub-species. B. longum subsp. infantis is a prevalent species in the breast-fed infant gut and the molecular mechanisms of HMO utilization for the type strain B. longum subsp. infantis ATCC 15697 (type strain) have been well characterized. We used growth, transcriptomic, and metabolite analysis to characterize key differences in the utilization of 2′FL, 3FL and DFL (FLs) between B. longum subsp. infantis Bi-26 (Bi-26) and the type strain. Bi-26 grows faster, produces unique metabolites, and has a distinct global gene transcription response to FLs compared to the type strain. Taken together the findings demonstrate major strain specific adaptations in Bi-26 to efficient utilization of FLs.

The genus Bifidobacterium: from genomics to functionality of an important component of the mammalian gut microbiota

“…suis and B. longum subsp. longum strains [68] , [159] , [160] , [161] , [162] , [163] , [164] , [165] , [166] , [167] . Not by chance, in silico investigations have revealed conserved gene clusters encoding ABC transporters with high affinity binding proteins, upstream regulatory elements and one or multiple GHs that, as a whole, represent the genetic arsenal through which the abovementioned bifidobacterial species degrade and internalize HMOs [9] , [11] .…”

“…Specifically, the B. longum subsp. infantis genome possesses a contiguous genomic segment encoding GHs active on the four HMO glycosidic linkages, represented by α-fucosidase, α-sialidase, β-galactosidase and β- N -hexosaminidase activities, and flanked by a cluster specifying an ABC transporter system composed of extracellular solute binding proteins and permeases, presumed to be required for HMO internalization [9] , [162] , [168] , [169] , [170] . However, due to the lack of identifiable secretion signals in the glycosidases produced by B. longum subsp.…”

Exploring the Ecology of Bifidobacteria and Their Genetic Adaptation to the Mammalian Gut

“…Recently, comparative genome analysis involving two strains of B. longum subsp. infantis (i.e., ATCC15697 and Bi-26) revealed that the metabolic enzymes involved in HMOs utilization appear to be conserved in this bifidobacterial taxon [ 85 ]. This comparative analysis was confirmed by metabolite analysis as well as transcriptomics assays suggesting that B. longum subsp.…”

“…infantis ATCC15697 is able to consume various HMOs simultaneously, whereas B. longum subsp. infantis Bi-26 is adapted to internalize relatively short and predominantly fucosylated HMOs [ 85 ]. In conclusion, these findings show that even though HMOs consumption is characteristic of B. longum subsp.…”

Architecture Insight of Bifidobacterial α-L-Fucosidases

“…On the other hand, there are several FMHGs investigated, and contrary to FHMOs, appear at lower concentration but showing a higher number of different forms including lactoferrin (17%), immunoglobulins IgG (<1%), IgM (<1%), and secretory IgA (11%) [9,10,11]. Both FHMOs and FHMGs stand out for their ability to stimulate the growth of bifidobacteria [7,12], whose metabolism transforms fucosylated oligosaccharides into short-chain fatty acids (SCFAs) such as acetate, formate, lactate, pyruvate [13], which in turn stimulate the immune system by inducing the differentiation of T-regulatory cells via inhibition of histone deacetylase [14].…”