Dynamics of fibers growing inside soft vesicles

We present 3D stochastic dynamic simulations of the growth of a semiflexible polymer inside a soft vesicle. We find that very stiff fibers stall soon and lock the membrane into a strongly deformed prolate shape. Fibers of intermediate stiffness buckle and form a toroidal configuration which distorts the membrane into an oblate shape. Finally, more flexible polymers form massive spool-like condensates with ordered domains, while the vesicle inflates isotropically. We discuss our results with respect to observations on cell shape in sickle red blood cells, developing erythrocytes, and genome packing inside bacteriophages. We quantify how the force felt by the fiber tip, and the vesicle aspect ratio, change during growth, and we discuss possible “synthetic biology" experiments to validate our results