24 ACTINOMYCETES 



ducing no aerial mycelium, forming no streptomycin, and sensitive to this 

 antibiotic; (b) a pigmented mutant, forming pink to vinaceous-colored 

 vegetative growth, but producing the typical aerial mycelium; this mutant 

 forms no streptomycin but gives rise to an antibiotic (rhodomycetin), 

 which is not active against gram-negative bacteria. 



Various strains of S. griseus produce at least two other antibiotics, one 

 of which, cycloheximide, is active only against fungi, and another, strep- 

 tocin, which is active against certain protozoan-like organisms. Streptocin 

 is present in limited amount in the culture nitrate of the organism and more 

 abundantly in the mycelium; it is soluble in organic solvents and is not 

 active against gram-negative bacteria. 



Bennett and Lindenfelser demonstrated that a majority of streptomycin- 

 producing strains of S. griseus form a green soluble pigment in calcium 

 malate medium and a yellow pigment in calcium succinate medium. On the 

 other hand, grisein-producing and nonstreptomycin-producing strains of 

 this organism do not form any green or yellow pigments in these media, 

 although they show the typical greenish pigmentation of the aerial myce- 

 lium. 



Okami examined 47 strains of streptomycin-producing cultures, 5 grisein- 

 producing strains, and 4 pink-pigment producers. He divided them into 

 three categories: 



1. The typical S. griseus cultures. 



2. Pink-pigment-producing forms. 



3. Those that do not produce any yellow pigment when grown on potato 

 plug. 



The streptomycin-producing strains grew in maltose-containing media 

 with NaN0 3 as a source of nitrogen, but not in glucose, glycerol, or sucrose 

 media. The grisein-producing strains grew in media containing the four 

 compounds. The pink-pigment strains grew only in glycerol media. The 

 utilization of the carbohydrate depends largely on the nitrogen source. In 

 the presence of ammonium sulfate, the above differences disappeared. All 

 strains utilized xylose, but not raffinose and rhamnose. Sensitivity to phage 

 was said to be strain specific, but not characteristic of streptomycin pro- 

 duction. The use of streptomycin-resistant and -dependent strains is supple- 

 mentary to the foregoing differentiation methods. 



Streptomyces flavus Group 

 The S. flavus group represents an extremely abundant group of organisms, 

 the individual members varying greatly in some of their cultural properties 

 on artificial media. This group has been known since 1891, when Rossi- 

 Doria described a culture under the name of Streptothrix albido-flava. An- 

 other culture was soon described by Gasperini, in 1892, as Actinomyces 



