Myxococcus xanthus strain M516E produced at least three related antibiotics against Gram-positive and Gram-negative bacteria. From physico-chemical properties, a main component was identical to myxovirescin A and a second component, designated M-230B was found to be an antibiotic which is closely related to myxovirescin A. The structure of M-230B was determined from its physico-chemical properties, especially from 13C NMR spectrum as compared with that of myxovirescin A. The addition of alcohol, such as isobutyl alcohol, to the culture medium markedly stimulated production of the antibiotics.