[Genetic instability of the feature of streptomycin resistance in Streptomyces erythraeus].

The feature of streptomycin resistance in S. erythraeus, a culture producing erythromycin, is genetically unstable. Mutants sensitive to 0.03 mg/ml of streptomycin are formed in the initial streptomycin resistant strains at a rate of 0.04 per cent. It was shown possible to perform step-by-step selection for increasing streptomycin resistance (from 0.2 to 15 mg/ml) in the mutants producing and not producing erythromycin. The increase in the streptomycin resistance did not lead to a higher resistance to other aminoglycosides. Restriction analysis of the total DNA with the use of various endonucleases demonstrated that the increase in the resistance was not associated with amplification of DNA nucleotide sequences.