Preparation of 14 C-labeled showdomycin.

When Streptomyces shoivdoensis (N2-209-56) mycelia were grown in the presence of sodium acetate-2-uC, the radioactive carbon from acetate-2-uC was fairly well incorporated into the showdomycin molecule ; with approximately 14 % of the total radioactivity of the added sodium acetate-2-14C being incorporated during a 10-hour incubation. Although three antibiotic substances were detected in the fermentation broth, the radioactive carbon from acetate2-uC was incorporated only into showdomycin. The radioactive showdomycin was extracted with methanol from the lyophilized powder of the fermentation broth, re-extracted with w-butanol, and finally purified by chromatography on a silicic acid column. Over 98.1% of the total radioactivity of this preparation was due to the 14C-showdomycin and approximately 0.33 juCi of the preparation corresponded to 1^mole of showdomycin. About 2.8 % of the radioactivity of the added sodium acetate-2-14C was recovered as that of the purified showdomycin-uC.