Unstable mutation of beta-lactamase production in Streptomyces lavendulae

Streptomyces lavendulae S55-B1 gave two distinct variants at an unusual high frequency: one is a beta-lactamase-nonproducing variant and the other is an Arg- variant. All of the Arg- variants concomitantly had no, or only very low, beta-lactamase activity and were unable to form aerial mycelia or spores. There was no significant linkage between the beta-lactamase activity and the other nutritional requirement which was analyzed. Two of the Arg- variants spontaneously gave Arg+ revertants at a very low frequency. The revertants, however, did not recover the beta-lactamase activity. It is suggested that the beta-lactamase gene may be capable of transposition with inactivation of the arg gene occurring frequently by insertion of the transposed element. Covalently closed circular deoxyribonucleic acid from S55-B1 was not detected by either cesium chloride-ethidium bromide buoyant density centrifugation or agarose gel electrophoresis.