126 ACTINOMYCETES 



Such cultures represent many species. Their growth is more commonly 

 colorless, but sometimes pigmented, smooth or lichnoid, leathery, compact, 

 with shiny surface. Some produce a soluble brown pigment. This was rec- 

 ognized by Krassilnikov, who designated such cultures as Actinomyces albus 

 sterilis and A. viridis sterilis, similar to the formation of Fungus sterilis. He 

 isolated from the soil about 100 such cultures. These were divided into 

 three groups: 



1. Strongly proteolytic cultures, capable of liquefying gelatin in 3-5 days, 

 of peptonizing milk in 6-10 days, with or without preliminary coagulation, 

 of hydrolyzing starch with varying degrees of rapidity, of inverting sugar 

 No growth on cellulose. Strongly antagonistic. 



2. Gelatin slowly liquefied, in 15-30 days, or not at all in that time; 

 milk coagulated and peptonized simultaneously; starch hydrolyzed with 

 varying degrees of rapidity or not at all. No growth on cellulose. Weak 

 antagonistic properties. 



3. Milk coagulated, due to acidification, but not peptonized. No antago- 

 nistic effects. 



In our collection, many of the cultures that originally produced aerial 

 mycelium have lost the capacity to do so, and can, therefore, no longer be 

 considered as type cultures. Streptomyces griseus, a vigorously growing 

 culture capable of producing streptomycin, yielded a mutant, which no 

 longer produces aerial mycelium, nor is it able to produce streptomycin. 



On the other hand, certain nocardia-like organisms have been isolated 

 from natural substrates, which, on continued cultivation on artificial media, 

 gave rise to variants which produced sporulating aerial mycelium. This is 

 true, for example, of the culture designated by Gause as Proactinomyces 

 cyaneus-antibioticus and thought to be identical with Beijerinck's Actino- 

 coccus cyaneus. Beijerinck believed in a close relationship between his cul- 

 tures and that of Streptomyces coelicolor Miiller. Whether these cultures are 

 naturally occurring sterile forms of Streptomyces, whether they are natural 

 mutants, or whether, as Gause belived, Streptomyces can be a mutant of 

 Nocardia (Proactinomyces), remains to be determined. 



