Cell shape independent FtsZ dynamics in synthetically remodeled cells

The FtsZ protein is a key regulator of bacterial cell division. It has been implicated in acting as a scaffolding protein for other division proteins, being a force generator during constriction, and more recently, as an active regulator of septal cell wall production. During an early stage of the division cycle, FtsZ assembles into a heterogeneous structure coined the \"Z-ring\" due to its resemblance to a ring confined by the midcell geometry. While in vitro experiments on supported lipid bilayers have shown that purified FtsZ can self-organize into a swirling ring roughly the diameter of a bacterial cell, it is not known how, and if, membrane curvature affects FtsZ assembly and dynamics in vivo.\n\nTo establish a framework for examining geometrical influences on proper Z-ring assembly and dynamics, we sculptured Escherichia coli cells into unnatural shapes, such as squares and hearts, using division-and cell wall-specific inhibitors in a micro fabrication scheme. This approach allowed us to examine FtsZ behavior in engineered \"Z-squares\" and \"Z-hearts\", and in giant cells up to 50 times their normal volume. Quantification of super-resolution STimulated Emission Depletion (STED) nanoscopy data showed that FtsZ densities in sculptured cells maintained the same dimensions as their wild-type counterparts. Additionally, time-resolved fluorescence measurements revealed that FtsZ dynamics were generally conserved in a wide range of cell shapes. Based on our results, we conclude that the underlying membrane environment is not a deciding factor for FtsZ filament maintenance and treadmilling in vivo.