Abstract
1. Several strains of antagonistic and non-antagonistic streptomyces were tested upon their abilities to grow on the streptomycin containing agar. Beside streptomycin producing ones, many strains were able to grow on the agar containing 10u/cc streptomycin, while only a limited number of streptomyces strains including streptomycin producing ones were capable to grow on the agar containing 100u/cc of streptomycin. Such a concentration of streptomycin, therefore, appeared to be specific and suitable for isolation and preservation of streptomycin producing
strains.
2. Even if the streptomyces strains producing other kind of antibiotics than strptomycin became to grow luxuriantly on streptomycin containing agar, there was seen no tendency to produce streptomycin.
3. It was able to select some, even if weakly, antibiotic colonies from the non-antagonistic strans of streptomyces by serial passages through streptomycin containing agars, although it was impossible to decide whether they were truely streptomycin producing ones, or not. The antibiotic strains thus obtained inhibited B. anthracis or Myco. phlei more strongly.
4. It was confirmed, that the streptomycin producing strains were reduced in colony numbers, became homogeneous in morphological properties and partially increased in inhibitory activities of culture filtrates, when they were cultivated on streptomycin containing agar through several generations.
