Nanoscale imaging of E. coli cells by expansion microscopy.

Expansion microscopy (ExM) is an emerging super-resolution imaging technology. ExM works by infusing a biological specimen with a superabsorbent hydrogel, followed by mechanical homogenization and isotropical expansion of the specimen in water. The unique and cost-effective process of ExM enables super-resolution optical imaging of sample of interest without the need to invest and use of a sophisticated microscope instrument. Here, we demonstrate that a nearly 3-fold isotropic physical expansion of E.coli fixed cells can be achieved in PBS, and the cell morphology during binary fission is clearly resolved in the expanded state, using a diffraction-limited microscope.