Waksman — 126 — Actinomycetes 



contradistinction to ability to form penicillin, which is a characteristic 

 property of the Penicillhim notatum—P. chrysogeniim group of fungi as 

 a whole. The streptomycin produced by the active strains of S. griseiis 

 was found to be made up of several chemical entities, namely, strepto- 

 mycin and mannosidostreptomycin. Certain other species of Stre-pto- 

 myces, such as S. hikiniensis (194), appear to produce an antibiotic 

 which is identical with streptomycin. Certain actinomycetes produce a 

 mixture of antibiotics, as streptomycin and streptothricin (428). One 

 of the methods of isolation of streptomycin is presented in Fig. 26. 



In order to select the more active streptomycin-producing strains it 

 is necessary to plate out the culture and pick colonies. These show con- 

 siderable variation in streptomycin production. Several substrains ob- 

 tained from No. 18-16, such as No. 4 and No. 9, are now largely used, 

 one being more active in certain laboratories, and the other in others. 

 Substrain No. 9 is also more susceptible to the actinophage. Strains 

 which gave an activity of 100 to 200 [J-g/ml. of streptomycin have been 

 developed to provide strains which give 400 to 500 [J-g/ml. and even 

 1,000 [;.g/ml. Irradiation with ultraviolet light, followed by picking cf 

 colonies, has given cultures which yield 600 to 800 [J.g/ml. The high- 

 est producing cultures in one medium are not always the highest in 

 another. A suitable medium must also be selected for inoculation pur- 

 poses in order to get high yields in the fermenter. 



The cultures are kept in a lyophilized state or are first grown on soil 

 then dried, or are continuously transferred on ordinary agar media (65). 



Various procedures can be used for the isolation of fresh cultures 

 of S. griseiis from natural substrates. Ordinary agar media are usually 

 employed, and colonies picked and tested. The S. griseiis strains can 

 be readily recognized by the pale green to grayish green shade of their 

 aerial mycelium. The agar used for plating purposes may also be en- 

 riched with streptomycin, as 25 or 50 mg/ml., to eliminate from the 

 plate the great majority of bacteria and other actinomycetes. To estab- 

 lish the identity of such cultures with streptomycin-producing strains 

 of S. grisens, the cultures are treated with S. griseiis actinophage (474). 

 The following method also offers certain advantages: A suitable agar 

 medium is seeded with living cells of a nonpathogenic strain of M. tu- 

 berculosis. The diluted soil suspension is added, and the plates are 

 incubated at 28°-30°C. to enable the actinomycetes to develop. This 

 is followed by incubation of the plates at 37 °C. to favor development of 

 the M. tuherculosis. The antagonistic colonies of the actinomycetes 

 will be surrounded by clear zones, free from the growth of the acid-fast 

 bacteria. By the use of this method. Woodruff and Foster (516) iso- 

 lated a substance, designated as streptin, which was similar in many 

 respects to streptothricin. 



Despite the fact that it is possible to isolate large numbers of S. 

 griseus strains, only very few of them will be found capable of produc- 



