Deciphering the tail proteins involved in the adsorption of Vp4 myophage to its Bacillus cereus hosts

Details

Supervisors

Gillis, Annika

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée

Abstract

The Vp4 myophage is a virus that infects the Bacillus cereus group, whose members are known for their pathogenic potential. The antimicrobial properties of this phage make it a promising candidate for biotechnology. Adsorption is the first step in the viral process of phages. This step is initiated by the interaction between the receptor binding proteins often located at the distal part of the tail fiber proteins and the bacterial receptors. This master’s dissertation aims to decipher the tail proteins involved in the adsorption of Vp4 myophage to its B. cereus hosts. Two candidate tail proteins involved in adsorption have been identified using bioinformatic tools. The first candidate is Gp112 (895 amino acids). Bioinformatic results suggested that Gp112 is a tail fiber protein containing an intramolecular chaperone in its C-terminal part. Additionally, tail fiber proteins generally harbor receptor binding proteins in their C-terminal regions, which are less conserved than their N-terminal parts. The receptor binding proteins allow the specific interaction between the phage and the host bacterium. The second candidate is Gp119 (831 amino acids). Bioinformatic results suggested that Gp119 is a baseplate wedge protein containing two carbohydrate binding modules, which allows the specific interaction between the Gp119 and the sugars decorating the bacterial cell wall surface. In this work, Gp112 and Gp119 were expressed as recombinant proteins fused to a GFP-tag and tested on several members of the B. cereus group. The binding capacity of the twos proteins was tested using the cell wall decoration assay with the fluorescence microscope. Gp119 showed a binding capacity to a limited number of strains compared to Gp112. However, the results revealed no clear correlation between these two proteins, indicating that Gp112 and Gp119 likely use different bacterial receptors and are complementary in the adsorption process. In this work, the search for a potential bacterial receptor for the B. thuringiensis BSGC 4BA1 strain was also conducted using the cell wall decoration assays. The results suggested that the collagen-like 2 protein is the bacterial receptor of the B. thuringiensis BSGC 4BA1 strain used by Gp112.