Chapter IV — 77 — Variations and Mutations 



strcptomvcin. On the other hand, the nonsporulating variant produced 

 no aerial mycehum, formed no streptomycin, was sensitive to the antibi- 

 otic action of this substance, was characterized by a tjq^e of growth that 

 in shaken cuhure underwent rapid lysis, and produced acid in the glu- 

 cose-containing medium. Both strains otherwise possessed the various 

 cultural properties which are characteristic of the S. griseus species as 

 a whole, such as lack of pigmentation in organic media and proteolytic 

 and diastatic properties. The nonsporulating strain, when isolated as 

 such, however, would hardly be recognizable as typical S. griseus. In 

 view of these variations, the question was raised: Is it possible that many 

 of the Nocardia species represent degenerate forms of Streptomyees? 

 Another variant of S. griseus produced a red-pigmented vegetative 

 growth. This was accompanied by a loss in capacity to produce strepto- 

 mycin; in its place another antibiotic, pigmented red and active only 



Table 8 : Production of streptothricin by tivo strains of 

 S. lavendulae and their variants (478) : — 



* Units of streptothricin produced in shaken cultures, after 4 

 days incubation. 



upon gram-positive bacteria, was formed. This culture if freshly iso- 

 lated from a natural substrate would definitely not be considered as 

 S. griseus. 



Another antibiotic-producing organism, S. lavendtdae, was also 

 found (478) to vary greatly in culture (Table 8). The variants dif- 

 fered in the amount and nature of soluble pigment in peptone-contain- 

 ing media, in the presence and nature of aerial mycelium and in its 

 pigmentation, and in the production of streptothricin. One strain of 

 the organism gave rise to two variants: one producing bluish colored 

 vegetative growth, initially blue diffusible pigment, and a lavender- 

 colored aerial mycelium with a slightly blue tinge; and the other pro- 

 ducing cream-colored vegetative growth, a soluble brown pigment in 

 peptone media, and a lavender-colored aerial mycelium. Two variants 

 were also isolated from sectors of colonies of another strain of S. laven- 

 dulae: one forming a white aerial mycelium, sometimes showing a faint 

 shade of pink; and the other devoid of aerial mycelium, except for a 

 scant growth of sporulating aerial hyphae on some of the old slants. 

 When the ability of these four variants to produce streptothricin in 



