Visualization of Single Escherichia coli Cells in the State of SOS Response using Expansion Microscopy

Expansion microscopy (ExM) is a sample preparation technique which allows to achieve improved visualization of biological structures based on the physical expansion of the sample. This method is used in combination with traditional light microscopy and allows to achieve visualization of biological structures with higher resolution, without the use of complex technical devices typical for super-resolution microscopy. Unlike the methods of super-resolution microscopy, expansion microscopy does not make it possible to overcome the diffraction limit; however, the observed effect can be considered equal to an increase in the spatial resolution. The relative simplicity of the method and low requirements for the microscope used, have made expansion microscopy a fairly popular method to visualize various biological structures recently. This paper describes the use of expansion microscopy to visualize DNA and structures formed by the FtsZ protein in Escherichia coli cells during the SOS response. The results of the work confirm the previously obtained data that the FtsZ protein in cells in the state of the SOS response is unevenly distributed. The protocol used in this work for visualization of E. coli cells using the expansion microscopy method can be used in the future to study the internal structures of other cells, both bacterial and eukaryotic.