Super-resolution images of peptidoglycan remodelling enzymes at the division site of Escherichia coli

Bacterial cells need to divide. This process requires more than 30 different proteins, which gather at the division site. It is widely assumed that these proteins assemble into a macromolecular complex (the divisome), but capturing the molecular layout of this complex has proven elusive. Super-resolution microscopy can provide spatial information, down to a few tens of nanometers, about how the division proteins assemble into complexes and how their activities are co-ordinated. Herein we provide insight into recent work from our laboratories, where we used super-resolution gSTED nanoscopy to explore the molecular organization of FtsZ, FtsI and FtsN. The resulting images show that all three proteins form discrete densities organised in patchy pseudo-rings at the division site. Significantly, two-colour imaging highlighted a radial separation between FtsZ and FtsN, indicating that there is more than one type of macromolecular complex operating during division. These data provide a first glimpse into the spatial organisation of PG-synthesising enzymes during division in Gram-negative bacteria.