Cryo-electron microscopy of the f1 filamentous phage reveals insights into viral infection and assembly

Phages are viruses that infect bacteria and dominate every ecosystem on our planet. As well as impacting microbial ecology, physiology and evolution, phages are exploited as tools in molecular biology and biotechnology. This is particularly true for the Ff (f1, fd or M13) phages, which represent a widely distributed group of filamentous viruses. Over nearly five decades, Ffs have seen an extraordinary range of applications, yet the complete structure of the phage capsid and consequently the mechanisms of infection and assembly remain largely mysterious. In this work, we use cryo-electron microscopy and a highly efficient system for production of short Ff-derived nanorods to determine a structure of a filamentous virus including the tips. We show that structure combined with mutagenesis can identify phage domains that are important in bacterial attack and for release of new progeny, allowing new models to be proposed for the phage lifecycle. In this work, the authors report a system for production of short versions of a filamentous phage enables the structure to be determined by cryo-electron microscopy. Structure combined with mutagenesis allows the identification of phage domains that are important in bacterial attack and for release of new viral progeny.

Automated summary

Phages, viruses that infect bacteria, are prevalent in every ecosystem on Earth and have various applications in molecular biology and biotechnology. The structure and mechanisms of infection and assembly of filamentous phages, particularly the Ff phages, have been largely unknown. In this study, the researchers used cryo-electron microscopy and a highly efficient system to produce short Ff-derived nanorods, successfully determining the structure of a filamentous virus including the tips. By combining the structure with mutagenesis, they identified important phage domains involved in bacterial attack and release of new viral progeny, leading to the proposal of new models for the phage lifecycle.