A large strain of viruses beat diseases with their Aztec-like shield

They called it ‘chimallin’

According to Assoc. Prof. Elizabeth Villa recent discoveries introduce a whole era of phage biology, and the shell outside the phage acts as a growing shield. Because of this growing shield, it was called “chimallin” to honor Aztec warriors.

As reported by phys.com, the study’s co-author Joe Pogliano, a professor in the Dapartment of Molecular Biology, has been studying these phages for more than 10 years. He believes nucleus-forming phages could be better for phage therapies against bacterial infections because they evolved to be naturally resistant to many types of bacterial defense systems.

“As we move toward the development of phage therapies, we’ll need to learn more about this newly discovered phage nucleus since it appears to make them better at attacking bacteria,” said Pogliano. The researchers, including Pogliano and Villa, also plan to collaborate with experts at UC San Diego’s Center for Innovative Phage Applications and Treatments, the first dedicated phage therapy center in North America.

Study abstract

“Bacteria encode myriad defences that target the genomes of infecting bacteriophage, including restriction–modification and CRISPR–Cas systems1. In response, one family of large bacteriophages uses a nucleus-like compartment to protect its replicating genomes by excluding host defence factors2,3,4. However, the principal composition and structure of this compartment remain unknown. Here we find that the bacteriophage nuclear shell assembles primarily from one protein, which we name chimallin (ChmA). Combining cryo-electron tomography of nuclear shells in bacteriophage-infected cells and cryo-electron microscopy of a minimal chimallin compartment in vitro, we show that chimallin self-assembles as a flexible sheet into closed micrometre-scale compartments. The architecture and assembly dynamics of the chimallin shell suggest mechanisms for its nucleation and growth, and its role as a scaffold for phage-encoded factors mediating macromolecular transport, cytoskeletal interactions, and viral maturation.”

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