Si) 



THK ACTIXOMVCKTKS, Vol. II 



of glycerol; make up the water content to 

 about 20 to 25 per cent. Sterilize the tubes 

 at 20 pounds for 20 minutes. The culture 

 strains are inoculated on this medium and 

 incubated at 28-30 o C. When the growth of 

 the organism is successful, white aerial my- 

 celium appears first on the surface of the 

 soil; when the culture matures the charac- 

 teristic color of the aerial mycelium is pro- 

 duced. 



There is always the danger that an old 

 culture, transmitted from one laboratory to 

 another, may either have become modified or 

 have lost some of its original properties. It 

 may have become contaminated, and the 

 contaminant may eventually replace the 

 original culture. One must also remember 

 that different investigators have often based 

 their descriptions of a particular species not 

 upon the original culture but upon subse- 

 quent isolates, which may or may not repre- 

 sent the same species. 



Finally, many holo-type cultures are not 

 available at all. Therefore, in some cases 

 type cultures are not reported. When re- 

 ported, they usually refer to the Institute of 

 Microbiology Collection (IMRU), the 

 American Type Culture Collection (ATCC), 

 or to the Agricultural Research Service 

 Culture Collection of the Northern Re- 

 gional Research Laboratory, U. S. Depart- 

 ment of Agriculture (NRRL). Other collec- 

 tions include Eidige Technischen Hochschule 

 (ETH) Zurich; Centraalbureau voor Schim- 

 melcultures (CBS) Baarn; and Institute of 

 Applied Microbiology, University of Tokyo 

 (IAM). 



Standard Media 



Some media are more favorable than oth- 

 ers for sporulation of Streptomyces cultures. 

 In view of the importance of sporulation in 

 characterizing a species (also in placing an 

 organism in the proper genus), it is essential 

 to select favorable media. Furthermore, since 

 some forms tend to lose the property of 



sporulation on continued growth, special 

 precautions must be taken in preserving 

 such cultures. The loss of aerial mycelium 

 may be reversible or irreversible. Since non- 

 sporulating streptomycetes may resemble 

 nocardiae and since certain nocardiae have 

 been reported to produce aerial mycelium 

 and spores similar to those of typical Strep- 

 tomyces cultures, the element of confusion 

 between the two genera always exists. 



Description of Streptomyces Species 



It is commonly believed that to charac- 

 terize a species it is essential to describe a 

 large number of its morphological and phys- 

 iological properties. This procedure is not 

 always helpful, especially if based upon un- 

 reliable criteria. The medium may not be 

 readily duplicated, or conditions of growth 

 may be different, or the inoculum may not 

 be prepared in the same way. Because of 

 these and other variations, many cultures 

 recently isolated have been described as new 

 species. Another reason is that it is much 

 easier to create a new species than to at- 

 tempt to correlate the characteristics of a 

 freshly isolated culture with those of known 

 species already described in the literature. 

 Numerous new species also have been 

 created to facilitate the obtaining of patents. 



Hesseltine et al. (1954) suggested that the 

 following steps be taken in the taxonomie 

 study of a Streptomyces species: 



1. Collection of strains on the basis of 

 pigmentation of aerial mycelium. 



2. Study of the morphology of strains 

 growing on a number of media favorable to 

 sporulation. 



3. Examination of the color of spores of 

 strains growing on optimum sporulating me- 

 dia. Five color groups were recognized: (a) 

 lavender, red, or pink; (b) blue, blue-green, 

 or green; (c) yellow; (d) white; (e) gray, 

 gray-brown, olive-gray, or dark gray. 



4. Study of cultural characters of strains 

 on various synthetic and organic media. 



