Bactericidal action of an antibiotic produced by Myxococcus xanthus

Myxococcus xanthus produced an antibiotic during the end of its exponential growth phase which was capable of inhibiting growth of several gram-positive and gram-negative bacteria. The antibiotic was bactericidal to growing cultures only; chloramphenicol inhibited the bactericidal action of the antibiotic. Upon addition of the antibiotic to Escherichia coli B, deoxyribonucleic acid and ribonucleic acid as well as turbidity of the culture continued to increase even after the viable count decreased; the culture lysed about 60 min after addition of sufficient concentrations of the antibiotic. Spheroplasts could be prepared if the antibiotic was added to a culture growing in the presence of high concentrations of sucrose and MgSO(4). Mutants of M. xanthus FB which are incapable of fruiting body formation or glycerol-induced myxospore formation also produced the antibiotic. A mutant of E. coli resistant to the purified antibiotic was isolated in order to study the role of the antibiotic in the predatory behavior of myxococci.