Biology subjects

Armbruster, E.

Publications and source records attributed to Armbruster, E..

3 recordsLinked to original sources

bioRxiv2022

Architecture and self-assembly of the jumbo bacteriophage nuclear shell

Bacteria encode myriad defenses that target the genomes of infecting bacteriophage, including restriction-modification and CRISPR/Cas systems. In response, one family of large bacteriophage employs a nucleus-like compartment to protect their replicating genomes by excluding host defense factors. However, the principle composition and structure of this compartment remain unknown. Here, we find that the bacteriophage nuclear shell assembles primarily from one protein, termed chimallin. 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 cooperatively self-assembles as a flexible sheet into closed micron-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.

biophysics↗

bioRxiv2021

A Cytoskeletal Vortex Drives Phage Nucleus Rotation During Jumbo Phage Replication inE. coli

Vortex-like arrays of cytoskeletal filaments that drive cytoplasmic streaming and nucleus rotation have been identified in eukaryotes, but similar structures have not been described in prokaryotes. The only known example of a rotating intracellular body in prokaryotic cells occurs when nucleus-forming jumbo phages infect Pseudomonas. During infection, a bipolar spindle of PhuZ filaments drives intracellular rotation of the phage nucleus, a key aspect of the replication cycle. Here we show the E. coli jumbo phage Goslar assembles a phage nucleus surrounded by an array of PhuZ filaments resembling a vortex instead of a bipolar spindle. Expression of mutant PhuZ strongly reduces Goslar phage nucleus rotation, demonstrating that the PhuZ cytoskeletal vortex is necessary for rotating the phage nucleus. While vortex-like cytoskeletal arrays are important in eukaryotes, this work identifies the first known example of a coherent assembly of filaments into a vortex-like structure driving intracellular rotation within the prokaryotic cytoplasm.

microbiology↗

bioRxiv2021

Subcellular Organization of Viral Particles During Maturation of Nucleus-Forming Jumbo Phage

Many eukaryotic viruses assemble mature particles within distinct subcellular compartments, but bacteriophages were long assumed to assemble randomly throughout the host cell cytoplasm. Here we visualized the subcellular location of viral particles formed during replication of Pseudomonas nucleus-forming jumbo phages and discovered that they assemble a unique structure inside cells we term phage bouquets. We show that after capsids complete DNA packaging at the surface of the phage nucleus, tails assemble and attach to the capsids, and these particles accumulate to form bouquets at specific subcellular locations. In these bouquets, the viral particles are arranged in a spherical pattern with tails oriented inward and the heads outwards. Localized at fixed distances on either side of the phage nucleus, bouquets grow in size and number over time as new phage particles are added. In the presence of mutations that cause the phage nucleus to be mispositioned away from its typical position at the midcell, bouquets still localize at the same fixed distance from the nucleus, suggesting an active mechanism for their formation and positioning. These results mark the discovery of a pathway for organizing mature viral particles inside bacteria and demonstrate that nucleus-forming jumbo phage, like most eukaryotic viruses, are highly spatially organized during all stages of their lytic cycle.

microbiology↗