Raising the bar: The efficacy of bioorthogonal reactions for bioconjugation has been thoroughly evaluated in four different biological settings. Powered by the development of new biocompatible ligands, the copper‐catalyzed azide–alkyne cycloaddition (see picture) has brought about unsurpassed bioconjugation efficiency, and thus it holds great promise as a highly potent and adaptive tool for a broader spectrum of biological applications.

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Members of the Bacteroidales order are among the most abundant gram-negative bacteria of the human colonic microbiota. These species decorate their cell surface glycoproteins with fucosylated glycans, which are believed to play important roles in host intestinal colonization. Currently, there is no method for the enrichment of these glycoproteins for their identification. Here, we describe a chemical approach directed toward labeling and detecting fucosylated glycoproteins from cultured Bacteroidales species, namely Bacteroides fragilis and Parabacteroides distasonis. We treated these bacteria with an alkyne-bearing fucose analog, which is metabolically integrated into the bacterial surface fucosylated glycoproteins. The alkyne-tagged glycoproteins can then react with azide-bearing biophysical probes via bioorthogonal click chemistry for detection or glycoproteomic analysis.