Resistance to streptomycin in a producing strain of Streptomyces griseus

Streptomyces griseus S104 was sensitive to streptomycin during exponential growth in a medium which, in the subsequent stationary phase, supported production of the antibiotic in yields above 200 µg/ml. When antibiotic production began cultures developed a tolerance toward their lethal metabolite. This was not due to an increase in pH associated with antibiotic production, since pH effects on streptomycin sensitivity in S. griseus were in the reverse direction. However, the degree of tolerance was directly related to the amount of cell materia1 present. Streptomycin production caused no change in the proportion of resistant variants in the population, nor did it cause the severe inhibition of protein synthesis observed in non-producing cultures exposed to the antibiotic. The lack of an effect on protein synthesis is attributed to the absence of streptomycin within the cytoplasm since soluble extracts from myceliurn harvested in the production phase were inactive when bio-assayed immediately after cell disuptionH. however, they developed antibacterial activity rapidly when heated, and more slowly when incubated at 25°C. The addition of phosphatase inhibitors during incubation prevented the appearance of antibiotic activitv, and it was concluded that a small amount of streotomvcin phosphate is present in the rnycelium during antibiotic production. Differences in (14C) streotomvcin uptake suggested that the myceliurn was appreciably less permeable to the antibiotic in the production phase than during exponential growth. However, a small amount was taken up and much of it was in the soluble fraction of disrupted cells. Bioassays showed that this 14C-labeled antibiotic within the cells had been partially inactivated, suggesting that conversion of streptomycin to an inactive derivative is involved in the mechanism which protects the organism from its metabolite.