16 



ACTINOMYCETES AS ANTAGONISTS 



is produced in both organic and synthetic media, the addition of a small 

 amount of agar increasing considerably the growth of the organism and 

 the production of the active substance. The addition to the medium of a 

 small amount of starch, as well as of phosphate and sodium chloride, was 

 also found to be favorable. S. antibioticus is strictly aerobic, and is able to 

 produce the active substance only under aerobic conditions that can be 

 brought about by growing it either in very shallow layers or in aerated 

 or agitated submerged growth. Actinomycin is extracted directly from 

 the medium by means of ether j the ether is then evaporated and the 

 substance taken up in alcohol. Further purification is accomplished by 

 means of petrol ether and passage through a chromatographic column, 

 as shown later (p. 171). 



Streftomyces lavendulae is capable of inhibiting the growth of many 

 gram-negative bacteria as well as of various gram-positive forms. The 

 antibiotic substance produced by this organism was designated as strep- 

 tothricin. The organism is grown in a tap-water medium containing i .0 

 per cent glucose, 0.5 per cent tryptone, 0.2 per cent K0HPO4, 0.2 per 

 cent NaCl, 0.00 1 per cent FeS04, and 0.25 per cent agar. The glucose 



TABLE 22. COMPARATIVE ACTIVITY OF TWO STRAINS OF S. LAVENDULAE 



From Waksman (926). 



Note. The organism was grown in i per cent starch medium. 



