214 



THE ACTINOMYCETES, Vol. I 



vealed that 20 to 50 per cent of all the cul- 

 tures of actiiiomycetes tested possessed an- 

 tagonistic properties. In some surveys the 

 percentage was higher, in some lower. Stapp, 

 for example, reported that 233 out of 477 

 cultures of streptomyccs isolated from soil 

 were active against B./usiformis. The nature 

 of the medium used for testing purposes is 

 of great importance, as shown by Johnstone 

 (Table 53). Most of the cultures were active 

 against gram-positive, including acid-fast, 

 bacteria; fewer were active against gram- 

 negati\'e bacteria and fungi. The majority 

 of antibiotic-producing actinomycetes are 

 found among the streptomycetes (Table 54). 

 Landerkin and Lochhead isolated from 

 different soils 50 actinomycetes antagonistic 

 to E. coH. When tested against different 

 bacteria, those actinomycetes that possessed 

 "the most intense antibiotic activity" were 

 also active upon "the greatest number of 

 bacterial species," in other words, had the 

 widest antibiotic spectrum (Fig. 82). A de- 

 tailed analysis of the results obtained by 

 Landerkin ct al. is presented in Table 55. 

 Here as well, fewer organisms were active 

 upon fungi than upon bacteria; of the latter, 

 the gram-positi\'e forms were most suscep- 

 tible, the gram-negative least. There were 



Table 55 



Antibiotic activity of 600 actinomycetes isolated 



from northern Canadian soils (Landerkin, 



Smith, and Lochhead) 



also marked differences in the degree of sen- 

 siti^'ity within each group; many more or- 

 ganisms were active upon E. coIi than upon 

 Ps. aeruginosa. 



Of 1,117 cultures of actinomycetes tested 

 by Aleshina and Makanovskaia, 44 per cent 

 were active against staphylococci and 19.4 

 per cent against the plague organism. Of 170 

 cultures isolated and tested by Alukherje and 

 Nandi, 40 per cent were active against gram- 

 positive bacteria, 21.1 per cent against gram- 

 negative bacteria, and 31.7 per cent against 

 fungi. Different isolates belonging to the 

 same species varied in their antagonistic 

 properties. Some of the cultures that exhib- 

 ited antagonistic effects when tested by the 

 agar streak method, did not form, in liquid 

 media, substances with the same kind of ac- 

 tivity. 



In a study of 70 strains of actinomycetes 

 for their antagonistic effect upon root-nodule 

 bacteria, Fogle and Allen found that 25 



* -|-4--|- = diameter of zone, 30 mm or more; 

 -!--(- = 20^29 mm; + = 10-19 mm; inactive = 

 less t liMii 10 mm. 



0. 25 



Figure 83. "Aiitil)i()tic index" ( 

 cetes in relation to depth of soil 

 from: Landerkin, G. B. et al. Can. 

 69(), 1950). 



)f act 

 (Rei)r 

 J. Re 



momy- 

 oduced 

 s. 28C, 



