Public Thesis Defense - ELI

Deciphering the molecular interactions between myophage Receptor Binding Proteins and their cognate receptors in the Bacillus cereus group by Manon NUYTTEN

Pour l'obtention du grade académique de doctorat en Sciences agronomiques et Ingénierie biologique

Phages are regaining interest in the context of the antimicrobial resistance crisis. To achieve their optimal use, understanding the fundamental mechanisms lying behind phage/host interactions is of prime importance. As the initial point of contact, the adsorption mechanism dictates the phage host spectrum through interaction between phage receptor binding proteins (RBP) and bacterial receptors. At the end of the phage life cycle, the lysis process allows the release of progeny phages through the concerted action of phage holins and endolysins. This thesis aims at bringing new insights into the adsorption and lysis mechanisms of Bacillus cereus phages, using Deep-Purple siphophage and Deep-Blue and Vp4 myophages. The first part of this work studied the biology of Vp4 myophage and characterized its endolysin. The second part focused on the viral and bacterial determinants governing the adsorption mechanism of B. cereus phages. It showed that the adsorption of B. cereus phages strongly relies on bacterial saccharidic moieties, interacting with phage proteins comprising carbohydrate binding modules. The RBPs were identified and their binding capacity to various B. cereus strains was experimentally confirmed. Then, the use of escape mutants resistant to Vp4 infection highlighted the implication of collagen-like proteins in the adsorption process of this phage. In the third part of this work, the holin and endolysin functions were investigated and revealed versatile lysis strategies. Finally, a collaborative work showcased the application of phage binding proteins under lateral flow assay format aiming at the rapid and selective detection of B. cereus.

Jury members :

• Prof. Jacques MAHILLON (UCLouvain) (Supervisor)
• Prof. Claude BRAGARD (UCLouvain) (Supervisor)
• Prof. Stephan DECLERCK (UCLouvain) (Chairperson)
• Prof. Pascal HOLS (UCLouvain)
• Prof. Rob LAVIGNE (KULeuven)
• Prof. Carlos SAO-JOSE (Lisbon Univ., Portugal)

The public defense of Manon NUYTTEN will also take place in the form of a videoconference

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