CLASSIFICATION OF THE ACTINOMYCETES 21 



media; this pigment may be due to lysis of the growth, which in some 

 strains or under certain conditions is olive-green to olive-buff (S. griseus). 

 One group, comprising a large number of species, is characterized by yellow 

 growth on various media and frequent production of a soluble yellow, 

 yellow-orange, golden, or greenish yellow pigment (S. flavus). The fifth 

 and sixth groups, which are also nonchromogenic, are characterized by 

 the production of red to red-orange and light red growth, with poorly de- 

 veloped, white to rose-white aerial mycelium or well-developed, pink aerial 

 mycelium (S. ruber and S. fradiae). Finally, a group has been added 

 because of its universal distribution, easy recognition, and the fact that it 

 includes the type species for the genus (S. albus). 



Streptomyces antibioticus Group 



This group was first recognized as a common and important group of 

 soil actinomycetes in 1941. It comprises a number of strains capable of 

 producing the antibiotic actinomycin, as well as a variety of nonactino- 

 mycin-producing strains. 



Species and cultures belonging to this group are characterized by the 

 production of a cream-colored growth, the color gradually turning brown. 

 The aerial mycelium is gray to dark gray, sometimes shaded yellowish or 

 even green. The soluble pigment in organic media is black to purplish. The 

 aerial mycelium is characterized by the production of straight spore-bearing 

 hyphae, arranged in clusters or broom-shaped bodies. The capacity to 

 produce aerial mycelium may be lost upon continued cultivation of the 

 cultures. 



This group comprises a number of species, notably S. antibioticus, S. 

 griseolus, S. fasciculus, and a number of other cultures that appear to be 

 synonyms of these. 



Streptomyces lavendulae Group 



This is the chromogenic group. The ability of certain cultures of actino- 

 mycetes to form soluble dark brown pigments in complex organic media was 

 first recognized by Rossi-Doria and Gasperini in 1891. Typical cultures were 

 described under the name Streptothrix chromogena or Actinomyces chromo- 

 genus. 



The group is widely distributed in the soil and is represented by numer- 

 ous types, which have been given a variety of names. The typical growth is 

 cream-colored to brownish. The aerial mycelium is well developed; it is 

 cottony in nature, at first white to light gray, becoming lavender or vinous 

 lavender. The sporophores usually form spirals. The spores are spherical to 

 oval, 0.5-0.8 n in diameter. The cultures are strongly proteolytic and 

 diastatic. They are characterized by production of brown to black soluble 



