CryoEM Investigation of Three-Dimentional Structure of the Stx-Converting Bacteriophage ϕ24B

A modified method for culturing, concentrating, and purifying phage ϕ24B preparations was developed. In particular, a new lysogenic phage-producing strain lacking flagella was used, induction conditions were optimized, and purification in a sucrose gradient followed by concentration by deposition on a Freon 113 cushion were used. Using this method, a preparation of the Stx-converting bacteriophage ϕ24B was obtained, suitable for CryoEM direct analysis. Based on CryoEM data for this phage, the first primary three-dimensional reconstruction of its virions was performed. The structure of the phage ϕ24B tail is described. It was shown that the adsorption apparatus of this virus is represented by six thin lateral fibrils, and an axial fibril located at the end of the tail. This arrangement of the tail structure is consistent with the previously proposed hypothesis based on analysis of the receptor binding proteins (RBPs) of this bacteriophage.