Waksman — 40 — Actinomycetes 



Litmus milk: Cream-colored ring. No coagulation; peptonized, with strong 

 alkaline reaction. 



Potato: Thin, wrinkled, cream-colored to yellowish. 



Nitrites produced from nitrates. 



Soluble brown pigment formed. 



Peptonization of milk and gelatin. 



Starch is hydrolyzed. 



Aerobic. 



Optimum temperature 37 °C. 



Habitat: Widely distributed in soils and other natural substrates. 



The first antibiotic produced by S. lavendiilae was designated as 

 streptothricin (452). Since then, several other antibiotics have been 

 isolated from members of this group. Some of these antibiotics, notablv, 

 lavendulin, streptolin and streptothricin VI, are similar to streptothricin 

 in their general antimicrobial spectra, but they differ in their quantita- 

 tive effects upon different bacteria, and in their greater or lower toxicity 

 to animals. Some of the antibiotics produced by organisms belonging 

 or closely related to the S. lavendiilae group are distinctly different from 

 streptothricin both chemically and in their antibiotic spectra, as is the 

 case for Chloromycetin. 



The streptothricin-producing S. lavendidae strains give rise to a 

 number of variants (478). Some of these variants produce on glucose- 

 peptone a blue diffusible pigment; others form a brown pigment. The 

 vegetative mycelium of the blue pigment-forming variants is pale-blue 

 with scattered, small pin-point areas of deep blue. Upon complete 

 sporulation, the vegetative growth is covered with thick lavender-colored 

 aerial mycelium; occasional sunken areas are of a slightly bluish tinge, 

 these areas corresponding to the pin-point regions of the deeper blue. 

 The under surface of the vegetative growth is cream-colored except for 

 the small blue spots. The other variants produce a colorless to cream- 

 colored vegetative growth free of any blue pigment whatsoever; one to 

 two days later, a brown diffusible pigment appears, the growth becom- 

 ing covered with abundant lavender-colored mycelium. On subse- 

 quent transfer on fungus-agar slants, the tw^o types of variants prove to 

 be rather stable. 



Some of the strains isolated from an actix'C streptothricin-producing 

 culture may lose the property of producing this antibiotic. Other 

 strains may form antibiotics which vary from the typical streptothri- 

 cin either in their antibacterial spectra or in their toxicity to animals. 



In a comparative study of the relation between growth of the organ- 

 ism and production of antibiotic, it was found (452) that both in sta- 

 tionary and in shaken cultures growth and activity reach a maximum 

 and then decline, the maximum for the first preceding somewhat that of 

 the second. Since the nitrogen in the dry mycelium varies between 7 

 and 9 per cent, growth may be expressed in terms of the dry weight of 

 the mycelium or in terms of its nitrogen content. It must be con- 

 cluded, therefore, that production of streptothricin is not a result of 



