Objective
Gut microbial microflora is composed of more than 1014 bacteria representing more than 200 species. It comprises both endogenous (resident) and exogenous (transiting) bacteria, which in healthy humans are kept under tight equilibrium. The participants 1 and 5 have developed simplified models in mice that represent a minimal resident flora capable of inhibiting implantation of C. difficile (Model 1) and C. perfringens (Model 2). In the latter model, preliminary data explaining the mechanism of inhibition have been obtained, whereas in the former model the mechanism remains to be explained.
The objectives concerning the Model 1 are twofold :
First, we shall attempt to elucidate how the barrier microbiota exert their inhibition towards C. difficile. Since no antibiotic substance has been identified that would explain this effect, we shall focus on the interactions between the three partners that are involved : the host, the barrier flora and C. difficile. We shall in particular investigate the adhesion to and degradation of mucus by mucinolytic enzymes by the barrier flora and C. difficile, and the composition of mucus at each step of implantation. This will give information concerning possible receptor structures for the barrier microbiota and may elucidate the potential role of these substances as nutrients, antimicrobial substances of chemoattractants. In addition, some of the genes coding for mucinolytic enzymes will be isolated in order to construct mutagenised barrier strains, which will shed further light on the nature of interactions between the barrier microbiota and the mucus layer that normally covers the intestine. Finally, further biochemical characterisation of the barrier strains will be attempted. Second, more information has to be gained about the target of the barrier, i.e. C. difficile. The virulence factors (adhesins, proteases) of this bacterium will be further studied at the genetic level by cloning, nucleotide sequence analysis, mutagenesis, and in vivo studies of mutant strains. Further studies elucidating regulation of toxin expression will be carried out and possible roles of surface associated structures (fimbriae, the S-layer) will be investigated.
With regard to Model 2, the antibiotic substance produced by the barrier flora will be further characterised by isolating and mutagenising the gene encoding this substance. The conditions of production of this substance will be investigated in vivo and epidemiological studies will be carried out in order to better define the ecological role of this antibiotic production.
Fields of science (EuroSciVoc)
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
- natural sciences biological sciences microbiology bacteriology
- natural sciences biological sciences genetics nucleotides
- natural sciences biological sciences biochemistry biomolecules proteins enzymes
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Coordinator
92296 CHATENAY-MALABRY CEDEX
France
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