Cryo-EM study of the glycan-specific 9NA siphophage infecting a Gram-negative host.

Bacteriophages are killers of bacteria, currently under investigation as alternative treatment against multi-resistant bacteria. Despite their growing use, little is known on their infection molecular mechanism. Our recent elucidation of siphophage T5 interaction with its bacterial protein receptor and consequent DNA ejection is a major landmark in this field (Linares et al, 2023), but our current knowledge does not cover the wide diversity of signals and interactions phages encounter at the bacterial envelop, even though siphophages represent the majority (60%) of all phages. We thus want to unravel the prototype structure of 9NA phage infecting Salmonella. It interacts with the LPS O-antigen motif exhibited by the bacteria. We aim at solving the structure of the whole phage prior interaction with the LPS, to characterize the stoichiometry and assembly of the proteins within the entire vision. Preliminary reconstructions are promising, we require new data to reach atomic resolution.