Probing Membrane-Associated Cytoskeletal Oligomers of the Bacterial Divisome by Electron Microscopy and Tomography

The cell division machinery or "divisome" of many bacteria, including Escherichia coli, contains homologs of tubulin (FtsZ) and actin (FtsA) that interact with each other to promote the synthesis of septal peptidoglycan. FtsA oligomers have an essential role as a track for tethering dynamically treadmilling FtsZ protofilaments to the cytoplasmic membrane. Other bacterial cytoskeletal oligomers such as MreB also assemble on and move along the membrane. Structures of these oligomers on membranes in vitro may mimic their behavior in the cell. Here, we describe a protocol to visualize FtsA oligomeric structures on membranes and their interactions with FtsZ protofilaments using negative stain transmission electron microscopy along with tomography.