22 ACTINOMYCETES 



pigment in protein-containing media. Many of the strains are strongly- 

 antagonistic and are capable of producing various antibiotics. 



This group comprises a number of species, of which the most important, 

 from the point of view of antibiotic production, are S. lavendulae and S. 

 venezuelae, the organisms that form streptothricin and chloramphenicol, 

 respectively. A number of other species have been described and numerous 

 cultures isolated capable of producing various antibiotics related to strep- 

 tothricin, including antibiotic 136, streptolin, and actinorubin. These cul- 

 tures appear to belong to the S. lavendulae group. 



Streptomyces lavendulae comprises numerous cultures extremely variable 

 in nature. Many of these cultures give rise, on cultivation, to different 

 mutants or variants. Some of these variants produce on glucose-peptone 

 agar a blue diffusible pigment; others form a brown pigment. The vegetative 

 mycelium of the blue pigment-forming variants is pale blue with scattered, 

 small pinpoint areas of deep blue. Upon complete sporulation, the vegeta- 

 tive growth becomes covered with the characteristic cottony lavender- 

 colored aerial mycelium; occasional sunken areas have a slightly bluish 

 tinge; the reverse of the vegetative growth is cream-colored except for the 

 small blue spots. Other variants produce a colorless to cream-colored vegeta- 

 tive growth free of any blue pigment whatsoever; a brown diffusible 

 pigment appears later, and the growth becomes covered with thick lavender- 

 colored mycelium. The two types of variants are stable in nature. Other 

 variants may lose the capacity to produce aerial mycelium. 



Streptomyces venezuelae, as well, produces a number of variants. Two 

 strains were isolated and found to be similar in their cultural and physi- 

 ological properties to S. lavendulae, although they differed in their ability 

 to utilize various carbohydrates. The S. venezuelae strains utilized arabinose, 

 rhamnose, xylose, lactose, and fructose; S. lavendulae either had no effect or 

 only a limited effect on these carbohydrates. The former also differed from 

 the latter in their sensitivity to actinophage and in various serological 

 reactions. 



S. venezuelae was described as having vegetative mycelium thin-walled, 

 colorless, hyaline, monopodially branched, the hyphae varying in diameter 

 from 0.9 to 1.8 n and the branches growing to about 150 /x in length. The 

 aerial mycelium is lavender under the microscope, thick-walled, generally 

 not much branched, straight or slightly and irregularly curved, not forming 

 spirals, individual hyphae arising frequently from the primary mycelium 

 at the surface of the substrate. The color of colonies when viewed on agar 

 without magnification is gray to light tan or pink, but not lavender. The 

 upper portions of the aerial hyphae divide into chains of spores. These are 

 oval to oblong, 0.4-0.9 by 0.7-1.6 /*. Individual spores are colorless at 



