Small angle X-ray scattering (SAXS) was used for the first time to study the self-assembly of the bacterial cell
division protein, FtsZ, with three different additives: calcium chloride, monosodium glutamate and DEAE-dextran
hydrochloride in solution. The SAXS data were analyzed assuming a model form factor and also by a modelindependent
analysis using the pair distance distribution function. Transmission electron microscopy (TEM) was used
for direct observation of the FtsZ filaments. By sectioning and negative staining with glow discharged grids, very high
bundling as well as low bundling polymers were observed under different assembly conditions. FtsZ polymers formed
different structures in the presence of different additives and these additives were found to increase the bundling of
FtsZ protofilaments by different mechanisms. The combined use of SAXS and TEM provided us a significant insight
of the assembly of FtsZ and microstructures of the assembled FtsZ polymers.