SUBSTANCES PRODUCED BY ACTINOMYCETES 191 



versible reduction-oxidation (probably quinone in nature) and several 

 others capable of acetylation (probably hydroxyls). The quinone-like 

 structure of the pigment is borne out by its sensitivity to alcoholic alkali, 

 and to hydrogen peroxide in the presence of sodium carbonate. In the 

 latter instance, the color rapidly disappears and a cleavage seems to 

 occur. 



Actinomycin in alcohol-water solutions is resistant to the action of 

 heat, being able to withstand boiling for 30 minutes. When such solu- 

 tions are made acid, however, boiling has a destructive effect upon the 

 activity of the substance, the extent of destruction being directly pro- 

 portional to the concentration of acid. The effect of alkali, however, is 

 much greater. Dilute alkali changes the color of the substance to light 

 brown, accompanied by a reduction in activity, which can be largely re- 

 stored when the solution is made neutral again. At a higher alkalinity 

 (0.25 N), especially at boiling temperature, the activity and reversibil- 

 ity are destroyed. Exposure of solutions to light for i to 3 months re- 

 duces the activity of the pigment very little. 



Streftothrkin 



Streptothricin is produced by Streftomyces lavendulae grown in a 

 medium containing glucose or starch ( i per cent) as a source of energy, 

 and tryptone, glycocoU, glutamic acid, or other organic nitrogenous 

 compound (0.3 to 0.5 per cent) as a source of nitrogen. Sodium nitrate 

 is a somewhat less favorable source of nitrogen. The organism is grown 

 in stationary, shallow cultures containing starch as a source of carbon 

 or glucose and a small amount of agar, or in submerged cultures. The 

 optimum temperature for the production of streptothricin is 23° to 

 25° C. (946). The relation between growth of the organism and pro- 

 duction of the antibiotic substance is brought out in Table 't^'t,. 



Streptothricin is soluble in water and in dilute mineral acids, but is 

 destroyed by concentrated acids. It is insoluble in ether, petrol ether, 

 and chloroform. In the crude culture-filtrate and in the alcohol-precipi- 

 tated form, streptothricin is thermolabile, whereas in the purified state 

 it is thermostable, withstanding 100° C. for 15 minutes. Treatment 

 with proteolytic enzymes does not reduce its activity. On adjusting the 

 reaction of the medium, when growth is completed, to ^H 3.5 with 



