Paulomycin C (Fig. 1) is a member of a novel class of antibiotics, the paulomycins, which are produced by Streptomyces paulus UC8560 and are active against a variety of pathogenic bacteria, including methicillin-resistant Staphylococcus aureus. Paulomycins A and B are esters of methylbutyric acid and isobutyric acid, respectively, and can be produced selectively through procedures involving precursor directed biosynthesis. Paulomycin C is an ester of propionic acid and has been detected in fermentations of S. paulus in synthetic medium to which methionine has been added. We now wish to report the effect of various concentrations of methionine on paulomycin C production.