Ribosomal Resistance to Streptomycin in Strains Regenerated from Protoplasts of a Streptomycin-Susceptible Mutant Derived from a Streptomycin Producer

When protoplasts of streptomycin-sensitive Streptomyces griseus KSN were regenerated to the mycelial form, streptomycin-resistant cultures appeared at a high frequency (approximately 1%). The resistance mechanism of the seregenerated cultures was different from that of ancestral streptomycin-producing Streptomyces griseus HUT 6037, from which the parent S. griseus KSN was derived. While the resistance to streptomycin of S. griseus HUT 6037 was due mainly to streptomycin-phosphorylating activity of streptomycin 6-kinase produced in the cells, the streptomycin-resistant cultures regenerated from protoplasts produced no streptomycin 6-kinase but the ribosomes changed and became resistant to streptomycin. In highly streptomycin-resistant cultures regenerated, one of the 30S ribosomal proteins was altered in electrophoretic mobility as compared to the corresponding protein of S. griseus KSN