SPECIES OF STREPTOMYCES 67 



variable. Hyphae on surface of agar 0.7 n in diameter; in shake flasks 0.7- 

 0.8 n; some of the submerged hyphae are much thicker, reaching 1.6 y. in 

 diameter. Formation of single spores at the end of the submerged sporula- 

 ting lateral branches. "Spores" form early, germinate readily, even while 

 apparently attached to hyphae. 



Aerial mycelium : Aerial hyphae formed in fascicles ; greenish yellow in 

 color, turning gray. Tendency to lose property of producing aerial myce- 

 lium. Tufts, with some curling of tips produced on certain media. On 

 glucose-asparagine agar, spores produced in chains, in whorls. No sporu- 

 lation on nutrient or glucose-nutrient agar. 



Synthetic agar: Limited growth, cream-colored to yellowish green tinge. 

 Generally, no aerial mycelium. No diffusible pigment. Hyphae penetrate 

 deep into agar. 



Nutrient agar: Thin growth, consisting of moist, isolated colonies, gray 

 to light green in color, with green to almost bluish tinge at bottom of slant 

 where colonies are confluent. White to gray nonsporulating aerial mycelium 

 appears much later. No diffusible pigment. 



Glucose-nutrient agar: Heavy lichnoid growth, yellowish brown to olive- 

 brown in color. Yellowish to gray aerial hyphae are abundant and appear 

 later, covering the whole surface of growth with a mat. Diffusible pigment 

 brownish or absent. 



Glucose-asparagine agar: Moist, flat, yellow to yellow-green colonies 

 growing deep into medium. Aerial hyphae frequently abundant; grayish 

 yellow to sulfur-yellow, later overgrown by white sporulating hyphae. Dif- 

 fusible pigment absent or faint yellow. 



Yeast-glucose agar: Heavy lichnoid growth, dark brown to olive-green 

 in color. Aerial hyphae pale to grayish yellow to greenish yellow, becoming 

 gray with age. Soluble brown pigment. 



Potato: Lichnoid growth, brownish to greenish yellow to dark olive-green 

 in color. Aerial hyphae absent, or formed as thin, yellowish layer on drier 

 portions of growth. Soluble pigment absent or dark brown. 



Gelatin: Limited growth in form of surface ring, canary-yellow in color. 

 No pellicle formed. Gelatin only slightly liquefied. Brown to dark brown 

 soluble pigment; this property may be lost on cultivation. 



Nutrient broth: Growth colorless in clumps on bottom of container; 

 soluble brown pigment, a property which may be lost on cultivation. 



Milk: Light yellow to brown surface ring. No coagulation; gradual pep- 

 tonization. 



Starch: Good hydrolysis. 



Carbon source: With yeast extract-mineral agar, there was no growth 

 over control on sucrose, lactose, or rhamnose; good growth on mannose 

 and glucose. 



Cellulose: Limited growth, no destruction of cellulose. 



