FAMILY III. STREPTOMYCETACEAE 



821 



gin green, central mass covered by gray 

 aerial mycelium. 



Potato agar: Fair growth, partly sub- 

 merged, covered with grayish white aerial 

 mycelium; medium becomes discolored. 



Blood agar: Heavilj^ textured small drab 

 colonies, aerial mycelium microscopical; 

 no hemolysis. 



Dorset's egg medium: Large, round, 

 colorless, scale-like colonies, radially 

 wrinkled; growth brownish, medium dis- 

 colored in 2 weeks. 



Serum agar: Smooth colorless discoid 

 colonies; marked umbilication after 2 

 weeks. 



Broth: Large fluffy white hemispherical 

 colonies, loosely coherent. 



Synthetic sucrose solution: A few large 

 round white colonies with smooth partly 

 zonate margins, lightly coherent in sedi- 

 ment; later smaller colonies in suspension 

 attached to side of tube. 



Milk: Coagulation; one-third peptonized. 



Carrot plug: Colorless raised colonies 

 with powdery white aerial mycelium; after 

 1 month, very much piled up, aerial myce- 

 lium gray; after 2 months, superabundant 

 growth around back of plug, confluent, 

 greatly buckled, all-over gray aerial my- 

 celium. 



Antagonistic properties : Positive. 



Source: Isolated from a case of strepto- 

 thricosis of liver (Willmore, Trans. Roy. Soc. 

 Trop. Med. Hyg., 17, 1924, 344). 



Habitat: Unknown. 



150. Sterile (non-conidia -forming) 

 .species. 



In view of the fact that various species of 

 Streptomyces are able to lose the capacity 

 to produce aerial mycelium, either on con- 

 tinued cultivation or by a sort of mutation, 

 cultures are obtained which may be mis- 

 taken for nocardias. They can be recognized, 

 however, by the structure of their vegeta- 

 tive mycelium and by their cultural and 

 physiological properties, such as forma- 

 tion of soluble pigments, liquefaction of 

 gelatin, hydrolysis of starch, inversion of 

 sucrose, coagulation and peptonization of 

 milk. Occasionally some are able to revert 

 to the typical streptomycete condition or 



to regain the capacity to produce aerial 

 mycelium. 



Such cultures represent many species. 

 Their growth is moi'e commonly colorless, 

 but sometimes pigmented, smooth or lich- 

 enoid, leathery, compact, with shiny surface. 

 Some produce a soluble brown pigment. This 

 was recognized by Krassilnikov, who desig- 

 nated 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 to 5 days, of pep- 

 tonizing milk in 6 to 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 to 30 

 days, or not at all in that time; milk coagu- 

 lated and peptonized simultaneously; 

 starch hydrolyzed with varying degrees of 

 rapidity or not at all. No growth on cellu- 

 lose. Weak antagonistic properties. 



3. Milk coagulated, due to acidification, 

 but not peptonized. No antagonistic effects. 



Waksman (in Waksman and Lechevalier, 

 Actinomycetes and Their Antibiotics, Balti- 

 more, 1953, 20) has used for these groups 

 such names as Streptomyces sterilis albus, 

 Streptomyces sterilis ruber, Streptomyces 

 sterilis viridis, Streptomyces sterilis flavus, 

 etc. to designate variant forms of cultures 

 which have lost the capacity to produce 

 aerial mycelium. In his collection many of 

 the cultures that originally produced aerial 

 mycelium have lost this capacity and could, 

 therefore, no longer be considered as typi- 

 cal. For example Streptomyces griseus, a 

 vigorously growing culture capable of pro- 

 ducing 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 hyphae. 

 This is true, for example, of the culture 

 designated by Gause as Proactinomyces 

 cyaneus-antibioticus and thought to be iden- 



