SOIL ACTINOMYCES 307 



2. Growth and aerial mycelium on synthetic agar green to dark- 



green; soluble brown pigment on synthetic media with most 

 carbohydrates A. viridochromogenus 



3. Deep brown to black pigment on synthetic agar: 



(a) Weakly growing organisms; orange-red growth on potato 



plug; no visible aerial mycelium on synthetic agar 



A . purpeochromogenus 



(b) Vigorously growing organisms; brown to black growth 



on potato plug; abundant cottony aerial mycelium on 

 synthetic agar A . pheochromogcnus 



4. Usually no action on milk (37°), accompanied by the darkening 



of the milk; mouse-gray aerial mycelium on synthetic agar; 

 ammonium salts used readily with different sources of 

 carbon A. aureus 



5. Brown pigment never produced on synthetic media: 



(a) Aerial mycelium on synthetic media has lavender shade 



A. lavendulae 



(b) Aerial mycelium on synthetic agar is abundant, of a 



water green color Actinomyces 218 



(c) Whirl formation in aerial mycelium on synthetic agar: 



(a') Growth colorless and aerial mycelium white 



A. reticuli 

 (b') Growth pink, aerial mycelium rose colored; nitrate 

 reduction very abundant; fewer whirls 



A. reticulum-ruber 



(d) Growth on synthetic agar sulfur-yellow, with yellow 



aerial mycelium; barnacle-like, greenish-yellow growth 

 on potato plug A. flavus 



(e) Growth on synthetic agar red colored, aerial mycelium 



abundant, orange colored; aerial hyphae usually do 

 not form spirals A . ruber 



II. Soluble pigment on organic media faint brown, golden, yellow or blue: 



1. Pigment blue, not always definite; soluble red pigment turning 



blue on synthetic agar A . violaceus -ruber 



2. Pigment at first green on organic media and synthetic agar, 



property lost on continued cultivation, becoming brown on 

 synthetic agar; aerial mycelium not produced on most media 



A. verne 



3. Soluble pigment at first brown, property lost entirely on con- 



tinued cultivation; growth and aerial mycelium on synthetic 

 agar abundant, white A. albus 



4. Soluble pigment yellowish green; growth on synthetic agar 



penetrating into the medium is pink A. calif ornicus 



5. Brown pigment produced only on certain protein media (usually 



gelatin and glucose broth, not nutrient agar) : 

 (a) Growth on synthetic agar red to pink; no differentiated 

 aerial mycelium or only scant white A. bobili 



