ANTAGONISTIC PROPERTIES 



115 



duced a substance that possessed a strong bactericidal action against a 

 large number of microorganisms. This substance was particularly active 

 against nocardias, mycobacteria, and micrococci ; it was less active upon 

 spore-bearing bacteria and had no action at all on nonspore-forming 

 bacteria, as illustrated in Table i6. Under the influence of the anti- 

 biotic factor, the microbial cells were either entirely lysed or killed with- 

 out subsequent lysis. The action upon spore-bearing bacteria was bac- 

 teriostatic but not bactericidal. The nonspore-forming bacteria, includ- 

 ing species of Rhizobiutn and Azotobacter, not only were not inhibited 

 but were actually able to develop in filtrates of the antagonists. 



Of 80 cultures of actinomycetes isolated from different soils, 47 pos- 

 sessed antagonistic properties, but only 27 of them secreted antibiotic 

 substances into the medium (Table 17). These agents were capable of 

 inhibiting the growth of gram-positive but not of gram-negative bac- 

 teria or fungi. The nature of the action of the various antagonists was 



TABLE 17. OCCURRENCE OF ANTAGONISTIC ACTINOMYCETES IN 

 DIFFERENT SOILS 



From Nakhimovskaia (671). 



found not to be identical. Some excreted water-soluble substances into 

 the medium, others did not. All the antibiotic agents were thermo- 

 stable, since heating for 30 minutes at 1.5 atmospheres only reduced 

 somewhat their activity. For those antagonists which did not excrete 



