Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 26, 2008
Publication Date: September 26, 2008
Citation: Price, N.P., Adeuya, A., Whitehead, T.R. 2008. Carbohydrate Metabolism in Bifidobacteria: Human Symbiotic Bacteria [abstract]. 11th Bratislava Symposium on Saccharides, Bratislava, Slovakia. p. 45. Technical Abstract: Bifidobacterium ssp. constitute up to 90% of microbial gut flora in the infant colon, but considerably less in adults. Carbohydrate metabolism in these bacteria is highly unusual. Data from four Bifidobacterium genomes indicates genes missing from glycolysis, gluconeogenesis, and the TCA cycle, including that for the key regulatory enzyme phosphofructokinase (PFK). A unique metabolic pathway, the "bifid shunt", is involved in a phospholytic cleavage of fructose-6-phosphate to erythrose-4-phosphate and acetyl phosphate, catalyzed by the enzyme fructose-6 phosphate phosphoketolase (F6PPK). Isotopic labeling experiments with **13C-fructose and several other labeled sugars indicate that the bifid shunt is the predominant pathway for the degradation of carbohydrates by Bifidobacterium ssp., by-passing glycolysis. The fractional distribution of **13C into carbohydrate and fatty acid metabolites was analyzed by GC-EI-MS. 2-Carbon units derived the bifid shunt are both secreted and incorporated into the Bifidobacterium de novo sugars and lipids. Moreover, several metabolic "chase" experiments have been undertaken using probiotic oligosaccharides, sialic acid, and human milk oligosaccharides, and differential pathways are reported for B. longum and B. infantis strains. These findings are consistent with the genome data for these strains, and suggest ways by which B. infantis has adapted to the environment of the infant human gut.