The Expandables: Cracking the Staphylococcal Cell Wall for Expansion Microscopy
T. Kunz, Marcel Rühling, Adriana Moldovan, Kerstin Paprotka, Vera Kozjak‐Pavlovic, Thomas Rudel, Martin Fraunholz
Abstract
Expansion Microscopy (ExM) is a novel tool improving the resolution of fluorescence microscopy by linking the sample into a hydrogel that gets physically expanded in water. Previously, we have used ExM to visualize the intracellular Gram-negative pathogens Chlamydia trachomatis , Simkania negevensis , and Neisseria gonorrhoeae . Gram-positive bacteria have a rigid and thick cell wall that impedes classic expansion strategies. Here we developed an approach, which included a series of enzymatic treatments resulting in isotropic 4× expansion of the Gram-positive pathogen Staphylococcus aureus. We further demonstrate the suitability of the technique for imaging of planktonic bacteria as well as endocytosed, intracellular bacteria at a spatial resolution of approximately 60 nm with conventional confocal laser scanning microscopy.