Liechti, G.W. et al. Nature doi:10.1038/nature12892 (11 December 2013).

Most bacterial species' cell walls contain peptidoglycan, a polymer essential for maintaining cell shape. Enzymes responsible for peptidoglycan synthesis are therefore important antibiotic targets. Though Chlamydiales bacteria contain genes for peptidoglycan synthesis and are susceptible to antipeptidoglycan antibiotics, to date, peptidoglycan has not been detected in any Chlamydial species. Liechti et al. report a metabolic labeling method that has now brought this decades-long debate about the 'Chlamydial anomaly' to rest. They took advantage of the tolerance of bacteria to accept alkyne- and azide-functionalized analogs of D-alanine-D-alanine dipeptides, which are incorporated into the growing peptidoglycan chain by the enzyme MurF. These bioorthogonal, reactive handles allow fluorescent probes to be attached via a click-chemistry reaction, allowing peptidoglycan to be visualized. The labeling method will facilitate a broad range of peptidoglycan studies in Chlamydia and in many other bacteria.