. The actinomycetes. Actinomycetales. 212 THE ACTINOMYCETES, Vol. I 60 TO SO SO 100 no 130. R. JAPONICUM Figure 82. Relative susceptibility of test organisms to antagonistic actinomj-cetes (E. coli = 100) (Reproduced from: Landerkin, G. B. and Lochhead, A. G. Can. J. Res. 26C: 505, 1948). procedures, with numerous modifications, have found extensive apphcations in the study of the antagonistic properties of ac- tinomycetes and have come to be known as screening methods. In 1935, the first comprehensive survey for the occurrence of antagonistic forms among actinomycetes, largely soil inhabit- a
. The actinomycetes. Actinomycetales. 212 THE ACTINOMYCETES, Vol. I 60 TO SO SO 100 no 130. R. JAPONICUM Figure 82. Relative susceptibility of test organisms to antagonistic actinomj-cetes (E. coli = 100) (Reproduced from: Landerkin, G. B. and Lochhead, A. G. Can. J. Res. 26C: 505, 1948). procedures, with numerous modifications, have found extensive apphcations in the study of the antagonistic properties of ac- tinomycetes and have come to be known as screening methods. In 1935, the first comprehensive survey for the occurrence of antagonistic forms among actinomycetes, largely soil inhabit- ants, was begun in Russia. Similar surveys of the occurrence of antibiotic-producing microorganisms, especially actinomycetes, were started in the United States in 1939. These surveys influenced greatly the whole subsequent history of antibiotics. General Surveys The first survey of the occurrence in soil of antagonistic actinomycetes was made by Nakhimovskaia. Out of 80 cultures of actino- mycetes isolated and tested, 47 were able to exert antagonistic effects, but only 27 pro- duced active substances. (Jram-positive bac- teria were inhibited, but not gram-negative bacteria or fimgi. No relation was observed between antagonism and formation of pig- ments, manner of sporulation, or shape of spores. Since the capacity to produce anti- bacterial substances was possessed by only certain cultures, it was suggested that this property could be utilized for the systemati- zation of species of actinomycetes. It was also suggested that various bacteria could be differentiated on the basis of their sensi- tivity to the actinomycetes. Krassilnikov and Koreniako found that many species of actinomycetes, members of the group now considered as the genus Streptomijccs, but not of Nocardia, produce substances that are strongly bac^tericidal against nocardias, mycobacteria, micro- cocci, and spore-forming bacteria, but not against gram-negative bacteria, lender the influence of these substances,
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