Diversity and Milk Oligosaccharide Consumption of Bifidobacterium pseudocatenulatum

Guy Shani, Dept. of Food Science and Technology and Foods for Health Institute,
University of California, Davis, USA

Guy Shani1,2, Jasmine Davis2,3, Josh Cohen1,2, Sadaf Nagshbandi4, Steve Ho1 Santiago Ruiz-Moyano2, Zac Lewis1,2, Mina Popovic2,5, Steven Frese2, Juliana DeMoura Bell1,2, Daniela Barile1,2, Carlito Lebrilla2,3, David Mills1,2
1:Department of food Science and Technology, University of California, Davis
2:Foods for Health Institute, University of California, Davis
3:Department of Chemistry, University of California, Davis
4: Department of Biochemistry and Molecular Biology, University of California, Davis
5:Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy

Human milk has been shown to enrich certain members of the genus Bifidobacterium in the infant gut. One species of this genus, Bifidobacterium pseudocatenulatum, has been found in multiple environments, including the gastrointestinal tracts of both human infants and adults. While this species has been frequently observed in breast fed infants, little work has been done to analyze the diversity of this organism with regard to possible genetic or physiological adaptations to the infant gut environment. To better understand this diversity, 62 members of the B. pseudocatenulatum species were isolated from various sources and analyzed for their phylogenetic relatedness by multilocus sequence analysis. Eleven unique isolates were then compared in their ability to utilize individual and pooled human milk oligosaccharides in an attempt to determine whether members isolated from breast-fed infants were capable of metabolizing these sugars. Four strains grew strongly on these human milk oligosaccharides and the specific sugar, 2-fucosyllactose and genomic sequencing indicated they possessed genes coding for fucosidases not present in the poor HMO consumers. Only one isolate possessed two distinct fucosidases, members of different glycosyl hydrolase families. These fucosidases were arranged as part of a cluster of genes with functions associated with consumption of fucosylated HMOs. The two fucosidases were expressed at higher levels during growth on HMOs and showed complementary in-vitro activity on different fucosylated HMO structures. The same strain also exhibited an ability to consume both lacto-N-tetraose and lacto-N-neotetraose, though at different rates, suggesting a preference for the former isomer. The unique ability to grow well on human milk oligosaccharides may partly explain some differences between infant- and adult-associated isolates, and will inform future synbiotic (prebiotic + probiotic) strategies for beneficially manipulating the infant gut microbiome.

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