Distribution ofIn VitroFermentation Ability of Lacto-N-Biose I, a Major Building Block of Human Milk Oligosaccharides, in Bifidobacterial Strains

Abstract

This study investigated the potential utilization of lacto-N-biose I (LNB) by individual strains of bifidobacteria. LNB is a building block for the human milk oligosaccharides, which have been suggested to be a factor for selective growth of bifidobacteria. A total of 208 strains comprising 10 species and 4 subspecies were analyzed for the presence of the galacto-N-biose/lacto-N-biose I phosphorylase (GLNBP) gene (lnpA) and examined for growth when LNB was used as the sole carbohydrate source. While all strains of Bifidobacterium longum subsp. longum, B. longum subsp. infantis, B. breve, and B. bifidum were able to grow on LNB, none of the strains of B. adolescentis, B. catenulatum, B. dentium, B. angulatum, B. animalis subsp. lactis, and B. thermophilum showed any growth. In addition, some strains of B. pseudocatenulatum, B. animalis subsp. animalis, and B. pseudolongum exhibited the ability to utilize LNB. With the exception for B. pseudocatenulatum, the presence of lnpA coincided with LNB utilization in almost all strains. These results indicate that bifidobacterial species, which are the predominant species found in infant intestines, are potential utilizers of LNB. These findings support the hypothesis that GLNBP plays a key role in the colonization of bifidobacteria in the infant intestine.Bifidobacteria are gram-positive anaerobic bacteria that naturally colonize the human intestinal tract and are believed to be beneficial to human health (21,30). Breastfeeding has been shown to be associated with an infant fecal microbiota dominated by bifidobacteria, whereas the fecal microbiota of infants who are consuming alternative diets has been described as being mixed and adult-like (12, 21). It has been suggested that the selective growth of bifidobacteria observed in breast-fed newborns is related to the oligosaccharides and other factors that are contained in human milk (human milk oligosaccharides [HMOs]) (3,4,10,11,16,17,34). Kitaoka et al. (15) have recently found that bifidobacteria possess a unique metabolic pathway that is specific for lacto-N-biose I (LNB; Gal␤1-3GlcNAc) and galacto-N-biose (GNB; Gal␤1-3GalNAc). LNB is a building block for the type 1 HMOs [such as lacto-N-tetraose

Unique Sugar Metabolic Pathways of Bifidobacteria

“…The presence of the GLNBP gene in various bifidobacterial strains coincides with their LNB utilization ability. 37) Some genes in the GNB/LNB operon of B. longum LMG13197 were found to be upregulated during growth in human milk. 43) Moreover, transcriptional responses of these genes were detected in fecal samples of breast-fed infants.…”

“…Moreover, Xiao et al investigated the utilization of LNB by many strains of bifidobacteria (208 strains comprising 10 species and four subspecies). 37) All the strains that naturally and predominantly colonize the infant GIT grew when LNB was used as sole carbohydrate source. In contrast, the strains that are found in adult GIT, human dental caries, and the guts of domestic animals are not able to utilize LNB.…”

“…106) D-Galactosyl-1,4-L-rhamnose was also produced using the corresponding phosphorylase. 107) Studies of the prebiotic effects of LNB on bifidobacteria in vitro 36,37) as well as its thermal decomposition mechanism 108) became possible only when the disaccharide became abundantly available due to this technology. LNB and GNB structures are found in biologically functional glycoconjugates, such as glycoproteins (O-glycans) and glycolipids (glycosphingolipids and blood type antigens).…”

Carbohydrate metabolism in Bifidobacteria

“…longum, B. longum subsp. infantis, B. breve, and B. bifidum, strains, which are the predominant species in infant intestines [55,164]. Therefore, LNB is presumed to be a natural prebiotic for bifidobacteria [56].…”

Unraveling the Leloir Pathway of Bifidobacterium bifidum: Significance of the Uridylyltransferases

“…This operon codes for a galacto-N-biose/lacto-N-biose I phosphorylase (LNBP), an Nacetylhexosamine 1-kinase (NahK), a UDP-glucose-hexose-1-phosphate uridylyltransferase (GalT2), and a UDP-glucose 4-epimerase (GalE2) (4). Metabolic profiling and genome sequencing of various B. bifidum strains reveal that a similar GNB/LNB gene cluster is present in this species, and the corresponding locus tags are listed in Table 1 (10)(11)(12)(13). However, this cluster is organized differently, as two sugar kinases lie between the coding sequences for LNBP and NahK (Fig.…”