title: Prebiotic galactooligosaccharides activate mucin and pectic galactan utilization pathways in the human gut symbiont Bacteroides thetaiotaomicron.
abstract: Galactooligosaccharides (GOS) are prebiotic carbohydrates that impart changes in the gut bacterial composition of formula-fed infants to more closely resemble that of breast-fed infants. Consuming human milk oligosaccharides (HMOs) provides specific bacterial strains with an advantage for colonizing the infant intestine. These same effects are seen in infants after GOS consumption, however GOS are very complex mixtures and the underlying molecular mechanisms of how GOS mimic HMOs are relatively unknown. Here we studied the effects of GOS utilization on a prominent gut symbiont, Bacteroides thetaiotaomicron, which has been previously shown to consume HMOs via mucin O-glycan degradation pathways. We show that several pathways for targeting O-mucin glycans are activated in B. thetaiotaomicron by GOS, as well as the galactan utilization sytem. Characterization of the endo-galactanase from this system identified activity on various longer GOS substrates while a subset of GOS compounds were identified as potential activators of mucin glycan metabolism in B. thetaiotaomicron. Our results show that GOS functions as an inducer of mucin-glycan pathways while providing a nutrient source in the form of β-(1 → 4)-galactan. These metabolic features of GOS mixtures may serve to explain the beneficial effects that are seen for GOS supplemented infant formula.
authors.affiliation: Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Groningen, The Netherlands.
authors.forename: Alicia
authors.initials: A
authors.lastname: Lammerts van Bueren
authors.affiliation: Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Groningen, The Netherlands.
authors.forename: Marieke
authors.initials: M
authors.lastname: Mulder
authors.affiliation: Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Groningen, The Netherlands.
authors.forename: Sander van
authors.initials: SV
authors.lastname: Leeuwen
authors.affiliation: Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Groningen, The Netherlands.
authors.forename: Lubbert
authors.initials: L
authors.lastname: Dijkhuizen
mesh_terms: D000070077:Bacteroides thetaiotaomicron / Q000187:drug effects / Q000378:metabolism*; D005685:Galactans / Q000378:metabolism*; D000069196:Gastrointestinal Microbiome / Q000187:drug effects; D041981:Gastrointestinal Tract / Q000382:microbiology*; D006026:Glycoside Hydrolases / Q000378:metabolism; D006801:Humans; D009077:Mucins / Q000378:metabolism*; D009844:Oligosaccharides / Q000494:pharmacology*; D010368:Pectins / Q000378:metabolism*; D056692:Prebiotics / Q000382:microbiology*; D013559:Symbiosis
chemical_list: D005685:Galactans; D009077:Mucins; D009844:Oligosaccharides; D056692:Prebiotics; D010368:Pectins; D006026:Glycoside Hydrolases; C094192:arabinogalactan endo-1,4-beta-galactosidase