Discovery of proteins involved in the interaction between prebiotics carbohydrates and probiotics & whole proteome analysis of the probiotic strain Bifidobacterium animalis susp. lactis BB-12

Ofir Gilad

    Research output: Book/ReportPh.D. thesis

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    Probiotic bacteria, which primarily belong to the genera Lactobascillus and Bifidobacterium, are live
    microorganisms that have been related to a variety of health-promoting effects. Prebiotics are indigestible
    food components that specifically stimulate the growth of probiotic organisms in the human
    gastrointestinal tract. Despite an increased scientific focus within this field, the mechanisms behind the
    beneficial effects exerted by pre- and probiotics are still far from fully understood.
    The purpose of the present industrial-PhD project was to identify proteins involved in
    interactions between the widely-used, extensively-studied probiotic strain Bifidobacterium animalis
    subsp. lactis BB-12 and potentially-prebiotic carbohydrates. The project was initiated with a screening
    phase in which more than 40 carbohydrates were tested for their ability to promote the growth of the
    bacterium. The results showed that BB-12 can utilise a wide range of oligosaccharides like galacto-, isomalto
    malto-, soybean-, xylo- and possibly also fructo-oligosaccharides.
    Xylo-oligosaccharides (XOS) have been selected for further studies with respect to the proteins
    that play a role in their catabolism in BB-12. These studies included comparative transcriptome and
    proteome analysis of samples obtained from BB-12 cultures grown on XOS (with glucose as a
    reference). These analyses indicated that the expression of a putative gene cluster with relevance for XOS
    catabolism is increased during growth on XOS. Based on these results and on chromatographic analysis
    of XOS consumption in BB-12 cultures, a model for XOS utilisation in BB-12 was established.
    The subsequent phase of the PhD project included extracellular proteome analysis, giving rise to
    the identification of 86 unique proteins. Of these proteins, 33 are potentially related to interactions
    between the bacterium and host intestinal cells. These interactions consist of adhesion, recruitment of
    human plasminogen and immunomodulation. In addition, proteins related to nutrient uptake and cell wall
    turnover were also found to be secreted by the bacterium.
    The final part of the project included the identification of 250 proteins (86 of them contain
    transmembrane segments) from the bacterial membrane fractions, including 61 proteins associated with
    transport systems with various predicted substrates such as oligosaccharides, amino acids and inorganic
    ions. In addition, 7 of the 8 subunits of the H+-ATPase enzyme complex and the majority of the proteins
    that embody the translocation machinery were identified.
    The results obtained in the present study may have an impact at both the scientific and the
    industrial levels. In addition to knowledge acquired regarding XOS catabolism in BB-12 and the
    implications on the design of a synbiotic preparation based on the two, the proteins identified in this
    study that are predicted to be involved in molecular mechanisms underlying probiotic effects or other
    essential physiological processes can serve as promising targets for detailed investigations, whose results
    may be of great relevance from both the applicable and scientific perspective.
    Original languageEnglish
    Place of PublicationKgs. Lyngby, Denmark
    PublisherTechnical University of Denmark
    Number of pages138
    Publication statusPublished - Oct 2010


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