Harnessing Fluorescent Moenomycin A Antibiotics for Bacterial Cell Wall Imaging Studies

The imaging of peptidoglycan (PGN) dynamics in living bacteria facilitates the understanding of PGN biosynthesis and wall-targeting antibiotics. The main tools for imaging bacterial PGN are fluorescent probes, such as the well-known PGN metabolic labeling probes. However, fluorescent small-molecule probes for labeling key PGN-synthesizing enzymes, especially for transglycosylases (TGases), remain to be explored. In this work, the first imaging probe for labeling TGase in bacterial cell wall studies is reported. We synthesized various fluorescent MoeA-based molecules by derivatizing the natural antibiotic moenomycin A (MoeA), and used them to label TGases in living bacteria, monitor bacterial growth and division cycles by time-lapse imaging, and study cell wall growth in the mecA-carrying methicillin-resistant Staphylococcus aureus (MRSA) strains when the β-lactam-based probes were unsuitable.