DNA amplification affects protease production and sporulation in Streptomyces fradiae.

Chloramphenicol resistance is an unstable character in Streptomyces fradiae, since spontaneous chloramphenicol-sensitive (Cmls) mutants arose at very high frequencies. One such Cmls mutant, DM14, showed DNA amplification as well. Extracellular protease activity was tenfold higher in DM14 when compared with its wild-type parent. Protease activity decreased considerably in DM14 when treated with spectinomycin, a treatment that reduces the copy number of amplified units of DNA. Sporulation in DM14 was delayed in the presence of spectinomycin at a concentration of 5 micrograms/ml, whereas the wild type was unaffected at that concentration. The results strongly indicated that the amplified DNA affected the two secondary metabolic functions, viz., protease production and the onset of sporulation in the mutant.