Siderophores play a vital role in the survival of bacteria, as they facilitate the transport of iron in low-concentration environments. Nature employs a variety of coordinating functional groups in siderophore scaffolds as a way of creating structural diversity. We have successfully shown that the pseudomonine synthetase can produce three distinct siderophore natural products and five siderophore-like compounds. The in vitro enzymatic production of acinetobactin has prompted a revision of the reported structure from an oxazoline to an isoxazolidinone. Our results reveal the inherent flexibility of the pseudomonine synthetase and thus provide insight into the evolution of siderophore biosynthetic gene clusters in bacteria.