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. Author manuscript; available in PMC: 2020 Jun 18.
Published in final edited form as: Cell. 2019 Jun 13;177(7):1771–1780.e12. doi: 10.1016/j.cell.2019.05.032

Figure 6. Model of Capsid Trafficking and the Role of Nucleus Rotation in Distributing Capsids around the Phage Nucleus.

Figure 6.

The spindle’s functions are complex and change as phage development proceeds.

(A) At the onset of infection, dynamically unstable filaments assemble with minus ends anchored at the cell poles, and plus ends oriented toward midcell push the growing phage nucleus to the cell midpoint where it oscillates in position.

(B) Model of dynamically unstable filaments showing cycles of polymerization, depolymerization, and recovery at the plus end of the polymer.

(C) Later in infection, the function of the spindle switches from centering the nucleus to rotating it in position and transporting capsids to the phage nucleus for DNA packaging. Treadmilling provides the driving force and temporally couples both processes.

(D) Model of treadmilling filaments showing addition of new subunits at the minus end near the cell pole drives photobleached subunits (purple) toward midcell.

(E) Rotation of the phage nucleus serves to distribute capsids evenly around its surface.

(F) Capsids are delivered to the surface of the phage nucleus for DNA packaging.