Siderophores, such as enterobactin (Ent), are small molecules that can be selectively imported into bacteria along with iron by cognate transporters. Siderophore conjugates are thus a promising strategy for delivering functional reagents into bacteria. In this work, we present an easy-to-perform, one-pot chemoenzymatic synthesis of functionalized monoglucosylated enterobactin (MGE). When functionalized MGE is conjugated to a rhodamine fluorophore, which affords RhB-Glc-Ent, it can selectively label Gram-negative bacteria that utilize Ent, including some E. coli strains and P. aeruginosa. V. cholerae, a bacterium that utilizes linearized Ent, can also be weakly targeted. Moreover, the targeting is effective under iron-limiting but not iron-rich conditions. Our results suggest that the RhB-Glc-Ent probe is sensitive not only to the bacterial strain but also to the iron condition in the environment.