High resolution reconstruction of a Jumbo bacteriophage infecting capsulated bacteria using hyperbranched tail fibers

Abstract

SUMMARYThe Klebsiella jumbo myophage ϕKp24 displays an unusually complex arrangement of tail fibers interacting with a host cell. In this study, we combined cryo-electron microscopy methods, protein structure prediction methods, molecular simulations, and machine learning approaches to explore the capsid, tail, and tail fibers of this phage at high resolution. We determined the structure of the capsid and tail at 4.3Å and 4.1Å resolution. We observed that the tail fibers were highly branched and rearranged dramatically upon cell surface attachment. This complex configuration involves fourteen putative tail fibers with depolymerase activity that provide ϕKp24 with the ability to infect a broad panel of capsular polysaccharide (CPS) types of Klebsiella pneumoniae. Taken together, our study provides structural and functional insight into how ϕKp24 adapts to the highly variable surfaces of capsulated bacterial pathogens, which will be useful for the development of phage therapy approaches against pan-drug resistant K. pneumoniae strains.