Project description:This work aimed to investigate the ability of two human-derived bifidobacterial strains, i.e. Bifidobacterium breve UCC2003 and Bifidobacterium longum NCIMB 8809, to utilize various oligosaccharides (i.e., 4-galactosyl-kojibiose, lactulosucrose, lactosyl-oligofructosides, raffinosyl-oligofructosides and lactulose-derived galacto-oligosaccharides) synthesized by means of microbial glycoside hydrolases. With the exception of raffinosyl-oligofructosides, these biosynthetic oligosaccharides were shown to support growth of at least one of the two studied strains. Short-chain fatty acid (SCFA) analysis by HPLC corroborated the suitability of most of the studied novel oligosaccharides as growth substrates for the two bifidobacterial strains, showing that acetate is the main metabolic end product followed by lactic and formic acids. Transcriptomic and functional genomic approaches carried out for B. breve UCC2003 allowed the identification of key genes encoding glycoside hydrolases and protein transport systems involved in the metabolism of 4-galactosyl-kojibiose and lactulosucrose. In particular, the role of β-galactosidases in the hydrolysis of these particular trisaccharides was demonstrated, highlighting their importance in oligosaccharide metabolism by human bifidobacterial strains.
Project description:It is increasingly recognised that the gastrointestinal microbiota plays a critical role in human health and promising evidence is accumulating that with dietary strategies, of prebiotic intervention, microbiota imbalances can be corrected and host health improved. Several prebiotics are widely used commercially in foods including inulin, fructo-oligosaccharides, galacto-oligosaccharides and resistant starches and there is convincing evidence, in particular for galacto-oligosaccharides, that prebiotics can modulate the microbiota and promote the growth of bifidobacteria in the intestinal tract of infants and adults. In this study we describe the identification and functional characterisation of the genetic loci responsible for the transport and metabolism of purified galacto-oligosaccharides (PGOS) by our model bifidobacterial strain, B. breve UCC2003. We further demonstrate that the extracellular endogalactanase specified by several B. breve strains, including B. breve UCC2003, is essential for metabolism of PGOS components with a long retention time and high degree of polymerisation. These PGOS components are transported into the bifidobacterial cell via various ABC transport systems and sugar permeases where they are further metabolised to galactose and glucose monomers that feed into the bifid shunt. This research described here advances our understanding of GOS metabolism by bifidobacteria and for the future there is great potential for exploiting bifidobacterial beta-galactosidase to create targeted prebiotics that can enrich for selected Bifiobacteria sp. and other beneficial microbes among the gut microbiota.
Project description:The global transcriptome of the Bifidobacterium animalis subsp. lactis Bl-04 was analyzed during exponential growth on 11 prebiotic carbohydrates and glucose to identify the specific gene cluster differentially upregulated in response to each carbohydrate.
Project description:Transcriptional and Functional Characterization of genetic elements involved in galacto-oligosaccharide utilisation by Bifidobacterium breve UCC2003
