Abstract
1) Fifty-eight representative ones out of 201 strains selected by the streak plate method (“primary screening” test) and proved to be effec-tive upon Gram-positive, Gram-negative and acid-fast bacteria, were cul-tivated on the surface of Waksman's media and the culture filtrates were tested for their activities and other biological properties by the broth dilu-tion method, by the cup method using 12 kinds of test bacteria, including E. coli, streptomycin resistant E. coli, Sta. aureus (Terashima strain), Sta. aureus 209-P and others (“secondary screening” test) and by the one-dimensional diffusion method.
2) By the procedure mentioned above 58 strains of actinomyces were subdivided into several types, which composed of many strains, whose antibiotics were almost identical with each other. The procedure enabled us, therefore, to identify the antibiotics contained in culture filtrates of many strains.
3) Several kinds of known and unknown antibiotics were isolated and purified in crystalline forms. They were found to belong for the most part to the streptomycin-streptothricin group. On the chemical and biological significances of each antibiotic reports will be made by each investigator elsewhere.
