A new technique that incorporates fluorescently labeled d-amino acids into bacteria makes it possible to observe biosynthesis of peptidoglycans, the major component of cell walls, in real time. The dynamics of cell- wall construction are incompletely understood, in part because of limitations in current techniques for observing peptidoglycan synthesis. “Commonly, these methods are labor-intensive, and their sensitivity suffers from their indirect and multiple-step nature,” write Yves V. Brun and Michael S. VanNieuwenhze of Indiana University, Bloomington, and coworkers in a paper in Angewandte Chemie International Edition (DOI: 10.1002/anie.201206749). To address that issue, the researchers constructed fluorescent d-amino acids that emit various colors. The compounds label peptidoglycans at sites of peptidoglycan synthesis in bacteria, and their fluorescence can be observed in the microbes’ newly synthesized cell walls. Different colors can be applied to the bacteria sequentially to monitor sites of peptidoglycan synthesis over time and obtain time-dependent images of cell-wall growth. “In combination with fluorescent fusion proteins, mutational analysis, and chemical perturbations, this methodology will allow a comprehensive analysis of the regulation and coordination of bacterial growth,” the researchers note.