SEARCH FOR ANTIBIOTICS: SCREENING PROGRAMS 



29 



Table 7 

 Inhibition of different actinomycetes by their respective antibiotics (Wak-sman et al., 1946) 



Antibiotic 



Actinomycin . 

 Streptothricin 

 Streptomycin 



Organism producing 

 antibiotic 



S. antibioticut 

 S. lavenclulae 

 S. griseiis 



* S. lutea units; crystalline material. 

 t E. coli units; crude preparation. 



Activity of prepara- 

 tion, per mg 



100,000* 



loot 



125t 



Inhibition of 



S. antibioticus 



10 



1 

 1 



6'. lavendulae 



mg/ml 



0.2 

 2500 

 10 



6'. griseus 



10 

 100 

 830 



these lost their activity on repeated trans- 

 fers in synthetic media. Among the sub- 

 stances so far isolated that possess anti- 

 trichomonal properties it is sufficient to 

 mention borrelidin and anisorhycin. 



Use of Antibiotics for Isolation of 

 Specific Antibiotic-producers 



The resistance of different organisms to 

 their own antibiotics and to closely related 

 forms can be utilized for isolating new strahis 

 of organisms producing specific antibiotics 

 and for obtaining even more potent strains 

 of such organisms. This phenomenon has 

 long been recognized (Table 7). Waksman, 

 Reilly, and Johnstone (1946) were the first 

 to suggest utilization of this property for the 

 isolation of organisms producing specific 

 antibiotics. This is further illustrated in 

 Table 8. 



In a study of a number of strains belong- 

 ing to the same species, or at least the same 

 series, of *S. lavendulae, Okami demon- 

 strated (Table 9) the high selectivity in the 

 antagonistic effects of one upon another. 

 The type culture of this species (No. 3330), 

 isolated in 191"), exerted no antibiotic action 

 upon any of the other strains; it was sensi- 

 tive, however, to three other cultures be- 

 longing to this group. Another culture, Xo. 

 oooo, likewise produced no antibiotic but 

 was sensitive to several other members of 

 the group. The original streptothricin- 

 producing culture, Xo. 3440-8, was active 



Table 8 



Inhibition of S. frcirliae 3554 by different antibiotics 



(Teillon, 1952) 



•^Water saturated solution. 



Table 9 



Reciprocal antagonism tjctween various S. 



lavendulae strains (Okami*) 



S. lavendulae 

 strain streaked 



3330... 

 3440-8 . 

 3516-W 

 3530... 

 3531 .. 



3532 

 3542. 

 3543. 

 3568. 

 3465 

 3544. 

 3555. 



Strain cross-streaked and inhibition 

 zone (mm) 



* Unpublished. 



