ANTAGONISTIC PROPERTIES 109 



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

 bacteria, as illustrated in Table 17. 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 Rhizobium and Azotobacter, not only were not inhibited 

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



Nakhimovskaia (628) found that antagonistic actinomycetes are 

 widely distributed in nature. Of 80 cultures isolated from different 

 soils, 47 possessed antagonistic properties, but only 27 secreted anti- 

 biotic substances into the medium (Table 18). These agents were ca- 

 pable of inhibiting the growth of gram-positive but not of gram-nega- 

 tive bacteria or fungi. The nature of the action of the various antagonists 



TABLE 18. OCCURRENCE OF ANTAGONISTIC ACTINOMYCETES IN 

 DIFFERENT SOILS 



From Nakhimovskaia (628). 



was found not to be identical. Some secreted 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 

 any substance into the medium, the presence of the growing antagonist 

 was essential in order to bring about an inhibition of bacterial develop- 



