Antibiotic TA was purified and crystallized from culture fluids of Myxococcus xanthus TA. The antibiotic (C34H57O9N, M.W. 623.8) contained the following functional groups: ketone, lactone, secondary amide, methoxy-substituted diene (λmax239 nm), primary alcohol and three secondary alcohols, two of which were cis-vicinal. Mild alkaline hydrolysis opened the lactone with concomitant loss of antibiotic activity. Periodate oxidation also destroyed biological activity.