AUTHOR=Kunz Tobias C. , Rühling Marcel , Moldovan Adriana , Paprotka Kerstin , Kozjak-Pavlovic Vera , Rudel Thomas , Fraunholz Martin 

TITLE=The Expandables: Cracking the Staphylococcal Cell Wall for Expansion Microscopy

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2021.644750

DOI=10.3389/fcimb.2021.644750

ISSN=2235-2988

ABSTRACT=<p>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 <italic>Chlamydia trachomatis</italic>, <italic>Simkania negevensis</italic>, and <italic>Neisseria gonorrhoeae</italic>. 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 <italic>Staphylococcus aureus.</italic> 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.</p>