26 ACTINOMYCETES 



b 8 . Aerial mycelium brown or chocolate. 

 Streptomyces thermofuscus 

 b 2 . Mesophilic form. 



Streptomyces flavochromogenes 

 b 1 . Aerial mycelium white or light gray. 

 a 2 . Nitrate reduced to free nitrogen. 



Streptomyces denitrificans 

 b 2 . Nitrate reduced to nitrite. 

 Streptomyces olivaceus 

 B. Excrete a soluble pigment into medium. 



1. Pigment brown on organic media; cultures absorb moisture from 

 air and condense it on aerial mycelium. 



Streptomyces hygroscopicus 



2. Cultures do not absorb moisture from air, pigment golden yellow. 



a. Weakly proteolytic, nonantagonistic. 



Streptomyces flaveolus 



b. Strongly proteolytic, strongly antagonistic. 



a 1 . Aerial mycelium white, becoming brownish gray to dark 

 drab-gray. 



Streptomyces aureofaciens 

 b 1 . Aerial mycelium between white and pallid quaker drab. 

 a 2 . Spirals formed. 



Streptomyces rimosus 

 b 2 . Spirals not formed. 



Streptomyces griseoflavus 

 Among the numerous other cultures that could be included in this group, 

 it is sufficient to list the following described in the literature: S. krainskii, 

 S. setonii, S. microflavus, S. flavoviridis, and S. longisporoflavus. 



Streptomyces ruber Group 



Members of this group have been known since 1889, when Mace" de- 

 scribed an organism under the name of Cladothrix rubra. Numerous other 

 cultures were later isolated and described, under different names, by 

 Krainsky, Waksman and Curtis, Krassilnikov, and many others. 



The group is characterized by bright red, red-orange, or rose-red vegeta- 

 tive growth, depending on the composition of the medium and conditions 

 of growth. The cultures may show considerable variation in pigmentation 

 of the vegetative growth, from purple-red to light rose. The pigment is 

 usually not excreted into the medium, unless the latter contains fatty sub- 

 stances in which the pigment is soluble. The aerial mycelium is not well 



