Structural basis of multimodal adsorption and infection initiation by Vibrio phage Peru-2

Abstract

Phage Peru-2, isolated during the 1993 cholera outbreaks in Peru, is distinct from the three ICP phage lineages typically associated with epidemic Vibrio cholerae. The molecular basis of Peru-2 adsorption and infection initiation has remained unknown. Here, we combine single-particle cryo-electron microscopy (cryo-EM) and cryo-electron tomography (cryo-ET) to define the architecture and infection mechanisms of Peru-2 at high resolution. The mature virion comprises an icosahedral capsid decorated with minor capsid proteins and a short tail apparatus surrounded by six structurally flexible tailspikes. These tailspikes are enzymatically active in mediating phage attachment to the Vibrio polysaccharide (VPS), a key component of biofilms. Three internal core proteins form a disordered core adjacent to the portal, positioning them for release before genome ejection during infection initiation. Structural analyses further resolve pre-ejection, genome-ejection, and post-ejection intermediates of the tail apparatus, while cryo-ET imaging of infected cells reveals a multimodal adsorption strategy during infection initiation. SignificanceVibrio phages play important ecological and evolutionary roles, yet the structural basis underlying their host recognition and adsorption strategies has remained poorly understood. Here, we determine the overall architecture of Vibrio phage Peru-2 at near-atomic resolution, showing that it shares a conserved molecular organization with T7-like podophages but possesses additional minor capsid proteins and a distinct tailspike. In addition, Peru-2 interacts extensively with both the bacterial cell surface and sheathed flagella, revealing multiple modes of adsorption strategy distinct from those of classic T7 infection. Our structural analyses and functional evidence that Vibrio polysaccharide is required for Peru-2 adsorption and infection provide a mechanistic framework for understanding host recognition and infection strategies among Vibrio phages.