Structure of the Chimalliviridae bacteriophage Goslar reveals host recognition and infection machinery

Large-genome bacteriophages (phages) of the Chimalliviridae family have a distinctive life cycle, building compartments inside infected bacterial cells that broadly protect their genomes from host defenses. Here, we use cryo–electron microscopy to determine a structure of the Escherichia coli –infecting Chimalliviridae phage Goslar. We combine manual modeling of 25 structural proteins with AlphaFold structure predictions of an additional three proteins to generate a composite model with 2888 protein chains from 28 different structural proteins, totaling more than 1.4 million amino acid residues. Our structure reveals the architecture of the Goslar capsid, portal, tail, and baseplate, highlighting structural similarities and differences with other tailed phages. Combining our structural data with quantitative mass spectrometry of Goslar virions, we identify several high-copy virion-associated proteins that likely play key roles when injected into host cells upon infection. We also identify a Chimalliviridae -specific family of proteins that form long, flexible filaments anchored at the phage baseplate and which incorporate carbohydrate-binding domains, suggesting a key role in host recognition.