Obafluorin is a β-lactone antibiotic produced by Pseudomonas fluorescens discovered by researchers at the Squibb Institute in 1984. Obafluorin is weakly active against Gram positive and Gram negative organisms, with a zone of inhibition against S. aureus of 7.4 – 8.7 mm, E. coli of 10.5 – 13.5 mm, E. cloacae of 9.3 mm, P. rettgeri of 7.7 mm and P. aeruginosa of 9.1mm at 10 µg/mL. Obafluorin is susceptible to hydrolysis by β-lactamases. Biosynthetically, obafluorin is catalysed by a rare non-ribosomal peptide synthetase.