Abstract
Recent reports highlight the efficacy of engineered mycobacteriophages to treat non-tuberculosis mycobacterial disease. Molecular insights into mycobacteriophage architecture and host interactions could allow structure-guided phage engineering to increase efficacy and broaden host range, but such information is currently unavailable. We describe the cryoelectron microscopy (cryo-EM) structure of mycobacteriophage Douge, which contains 1,105 protein subunits assembled into a complete siphophage and is coated with glycan-binding domains for mycobacterial cell surface interactions. When filled with viral genome, the channel spanning the connector, tail, and baseplate is sealed by tape measure proteins, providing a genome gating system and requiring limited structural changes for genome ejection upon phage-host contact. Nanometer-resolution cryoelectron tomography (cryo-ET) snapshots of phage-host interactions show that the baseplate remains attached to the mycobacterial outer membrane during viral genome ejection. This study reveals high-resolution structural details of this mycobacteriophage and its interaction with host glycans.