SPECIES OF THERMOACTINOMYCES 131 



Blood serum: Good, smooth growth; liquefaction positive. 

 Temperature: Optimum 37°-55°C; grows poorly at 27°C and not at all 

 at 60°C. 

 Source: Self -heated hay. 



3. Thermoactinomyces thalpophilus Waksman and Corke (Waks- 

 man, S. A., and Corke, C. T., J. Bacterid., in press). 



Vegetative growth: Good growth on organic and synthetic media, ex- 

 cept on potato, at 50°C. Growth colorless with yellow pigmentation in 

 edges; color changing to orange with age of culture. Soluble pigment 

 wine-colored to light rose produced in yeast-glucose agar. 



Aerial mycelium: Well-developed; white, powdery, with tendency to 

 form "fairy rings" on some media. Sporulating hyphae very short, 0.6-1.0 n 

 in length. Spherical conidia, 0.8-1.5 n in diameter, are produced singly on 

 the short sporophores or are entirely sessile. 



Synthetic sucrose agar: Abundant colorless growth; powdery white to 

 light-gray aerial mycelium. 



Potato: Limited vegetative growth; limited powdery, white aerial 

 mycelium. 



Gelatin: Liquefaction positive. 



Milk: Coagulation, with limited peptonization. 



Starch: Rapid hydrolysis. 



Nitrate: Limited reduction to nitrite. 



Nutrient-glycerol agar: Cream-colored vegetative growth; white aerial 

 mycelium. 



Glucose-asparagine agar: Colorless growth; white, powdery aerial my- 

 celium; reverse of growth white to yellow to light brown. Considerable 

 development of "fairy rings" in aerial mycelium. 



Yeast-glucose agar: Good, colorless growth, pigmented yellow at edges, 

 color turning orange in older cultures; lichnoid, white aerial mycelium; 

 soluble wine-colored to rose pigment. 



Temperature: No growth at 28°C; good growth in 4 days at 37°C; 

 excellent growth in 2 days at 50°C. 



Source: Soil; high temperature composts. 



