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CARACTERISATION BIOCHIMIQUE ET STRUCTURALE DE BACTERIOCINES CIBLANT LE METABOLISME DU PEPTIDOGLYCANE BACTERIEN, ALTERNATIVE POTENTIELLE AUX ANTIBIOTIQUES.

Abstract : The misuse of antibiotics during the last decades led to the emergence of multidrug resistant pathogenic bacteria. This phenomenon constitutes a major public health issue. Given that urgency, the finding of new antibacterials in the short term is crucial.Colicins, due to their antimicrobials properties, constitute good candidates. They are protein toxins produced by E. coli to kill competitors belonging to the same or related species. In most cases, they exhibit their cytotoxic activity through an ionophoric or nucleasic activity. Among the twenty colicins known to date, colicin M (ColM) is the only one known to interfere with peptidoglycan biosynthesis. It develops its lethal activity in the E. coli periplasm, in three steps deeply linked to its structural organization in three domains. Once in the periplasm, ColM degrades the lipid II, i.e. the last precursor in the peptidoglycan biosynthesis pathway, in two products that cannot be reused, thereby leading to cell lysis. Several ColM homologues have been identified in other bacterial genera, such as Pseudomonas, Pectobacterium and Burkholderia, but no cross activity has been shown to date, explaining the narrow antibacterial spectrum displayed by the members of this new family of antibacterial enzymes.This work deals with the structural and biochemical study of ColM and some of its homologues. Structural studies on several variants of PaeM, the ColM homologue from P. aeruginosa, led to identify a conserved water molecule in the active site, probably playing a central role in the catalytic mechanism of this enzyme family. Moreover, expression of ColM homologues from Pseudomonas or Pectobacterium species directly in the E. coli periplasm showed that all these homologues were able to induce E. coli cell lysis, thus demonstrating the great potential of these bacteriocins as an alternative to antibiotics. Following these results, several chimera colicins were created between ColM and its homologues, which were shown to degrade lipid II in vitro and to induce E. coli cell lysis after their periplasmic expression, opening the way to future new therapeutic options.
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https://tel.archives-ouvertes.fr/tel-01828072
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Submitted on : Tuesday, July 3, 2018 - 1:03:00 AM
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Dimitri Cherier. CARACTERISATION BIOCHIMIQUE ET STRUCTURALE DE BACTERIOCINES CIBLANT LE METABOLISME DU PEPTIDOGLYCANE BACTERIEN, ALTERNATIVE POTENTIELLE AUX ANTIBIOTIQUES.. Biochimie, Biologie Moléculaire. Université Paris-Saclay, 2017. Français. ⟨NNT : 2017SACLS529⟩. ⟨tel-01828072⟩

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