An Infant-associated Bacterial Commensal Utilizes Breast Milk Sialyloligosaccharides

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bBifidobacteria constitute a specific group of commensal bacteria that inhabit the gastrointestinal tracts of humans and other mammals. Bifidobacterium breve UCC2003 has previously been shown to utilize several plant-derived carbohydrates that include cellodextrins, starch, and galactan. In the present study, we investigated the ability of this strain to utilize the mucin-and human milk oligosaccharide (HMO)-derived carbohydrate sialic acid. Using a combination of transcriptomic and functional genomic approaches, we identified a gene cluster dedicated to the uptake and metabolism of sialic acid. Furthermore, we demonstrate that B. breve UCC2003 can cross feed on sialic acid derived from the metabolism of 3=-sialyllactose, an abundant HMO, by another infant gut bifidobacterial strain, Bifidobacterium bifidum PRL2010.

Section: Discussionmentioning

confidence: 93%

mentioning

confidence: 90%

Metabolism of Sialic Acid by Bifidobacterium breve UCC2003

Egan

Motherway

Ventura

et al. 2014

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“…Oligosaccharides were purified from a cranberry derivative through reverse-phase C 18 and size exclusion chromatography (see Fig. S1 in the supplemental material).…”

Section: Resultsmentioning

confidence: 99%

“…In contrast, the chromosome of the phylogenetic near neighbor and infant-colonizing bacterium B. longum subsp. infantis contains genes that enable human milk oligosaccharide utilization within the nursing infant gut (15)(16)(17)(18). In general, B. longum subsp.…”

Section: Importancementioning

confidence: 99%

A Human Gut Commensal Ferments Cranberry Carbohydrates To Produce Formate

Özcan

Sun

Rowley

et al. 2017

Self Cite

Commensal bifidobacteria colonize the human gastrointestinal tract and catabolize glycans that are impervious to host digestion. Accordingly, Bifidobacterium longum typically secretes acetate and lactate as fermentative end products. This study tested the hypothesis that B. longum utilizes cranberry-derived xyloglucans in a strain-dependent manner. Interestingly, the B. longum strain that efficiently utilizes cranberry xyloglucans secretes 2.0 to 2.5 mol of acetate-lactate. The 1.5 acetate:lactate ratio theoretical yield obtained in hexose fermentations shifts during xyloglucan metabolism. Accordingly, this metabolic shift is characterized by increased acetate and formate production at the expense of lactate. α-l-Arabinofuranosidase, an arabinan endo-1,5-α-l-arabinosidase, and a β-xylosidase with a carbohydrate substrate-binding protein and carbohydrate ABC transporter membrane proteins are upregulated (>2-fold change), which suggests carbon flux through this catabolic pathway. Finally, syntrophic interactions occurred with strains that utilize carbohydrate products derived from initial degradation from heterologous bacteria. IMPORTANCE This was a study of bacterial metabolism of complex cranberry carbohydrates termed xyloglucans that are likely not digested prior to reaching the colon. This is significant, as bifidobacteria interact with this dietary compound to potentially impact human host health through energy and metabolite production by utilizing these substrates. Specific bacterial strains utilize cranberry xyloglucans as a nutritive source, indicating unknown mechanisms that are not universal in bifidobacteria. In addition, xyloglucan metabolism proceeds by using an alternative pathway that could lead to further research to investigate mechanisms underlying this interaction. Finally, we observed cross-feeding between bacteria in which one strain degrades the cranberry xyloglucan to make it available to a second strain. Similar nutritive strategies are known to occur within the gut. In aggregate, this study may lead to novel foods or supplements used to impact human health through rational manipulation of the human microbiome.

“…In addition, several different strategies are employed by groups of Bifidobacterium to utilize HMOs. B. infantis ATCC 15697 is believed to import HMOs intact and subsequently to employ intracellular glycoside hydrolases, such as ␤-galactosidases, N-acetyl-␤-D-hexosaminidases, ␣-fucosidases, and ␣-sialidases, to deconstruct HMOs (31)(32)(33)(34)(35). In contrast, other species of Bifidobacterium (e.g., B. bifidum) employ extracellular glycosidases to sequentially degrade these structures and to transport mono-, di-, or oligosaccharides rather than the complex, compositionally diverse, and often branched structures which comprise HMOs (31).…”

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confidence: 99%

Oligosaccharides Released from Milk Glycoproteins Are Selective Growth Substrates for Infant-Associated Bifidobacteria

Karav

Parc

Bell

et al. 2016

Self Cite

128

110

Milk, in addition to nourishing the neonate, provides a range of complex glycans whose construction ensures a specific enrichment of key members of the gut microbiota in the nursing infant, a consortium known as the milk-oriented microbiome. Milk glycoproteins are thought to function similarly, as specific growth substrates for bifidobacteria common to the breast-fed infant gut. Recently, a cell wall-associated endo-␤-N-acetylglucosaminidase (EndoBI-1) found in various infant-borne bifidobacteria was shown to remove a range of intact N-linked glycans. We hypothesized that these released oligosaccharide structures can serve as a sole source for the selective growth of bifidobacteria. We demonstrated that EndoBI-1 released N-glycans from concentrated bovine colostrum at the pilot scale. EndoBI-1-released N-glycans supported the rapid growth of Bifidobacterium longum subsp. infantis (B. infantis), a species that grows well on human milk oligosaccharides, but did not support growth of Bifidobacterium animalis subsp. lactis (B. lactis), a species which does not. Conversely, B. infantis ATCC 15697 did not grow on the deglycosylated milk protein fraction, clearly demonstrating that the glycan portion of milk glycoproteins provided the key substrate for growth. Mass spectrometry-based profiling revealed that B. infantis consumed 73% of neutral and 92% of sialylated N-glycans, while B. lactis degraded only 11% of neutral and virtually no (<1%) sialylated N-glycans. These results provide mechanistic support that N-linked glycoproteins from milk serve as selective substrates for the enrichment of infant-associated bifidobacteria capable of carrying out the initial deglycosylation. Moreover, released N-glycans were better growth substrates than the intact milk glycoproteins, suggesting that EndoBI-1 cleavage is a key initial step in consumption of glycoproteins. Finally, the variety of N-glycans released from bovine milk glycoproteins suggests that they may serve as novel prebiotic substrates with selective properties similar to those of human milk oligosaccharides. IMPORTANCEIt has been previously shown that glycoproteins serve as growth substrates for bifidobacteria. However, which part of a glycoprotein (glycans or polypeptides) is responsible for this function was not known. In this study, we used a novel enzyme to cleave conjugated N-glycans from milk glycoproteins and tested their consumption by various bifidobacteria. The results showed that the glycans selectively stimulated the growth of B. infantis, which is a key infant gut microbe. The selectivity of consumption of individual N-glycans was determined using advanced mass spectrometry (nano-liquid chromatography chip-quadrupole time of flight mass spectrometry [nano-LC-Chip-Q-TOF MS]) to reveal that B. infantis can consume the range of glycan structures released from whey protein concentrate. P rotein glycosylation is a common modification that adds a major dimension of complexity to protein structure and has been linked to significant roles in protein fun...