NATURE OF ANTIBIOTIC SUBSTANCES 127 



action of the lipoid is greatly impaired under those conditions j the pres- 

 ence of the living actinomyces is generally necessary, since free lipoid 

 should be secreted in the susceptible suspension. 



Certain actinomycetes can produce agents that are capable of exerting 

 a lytic effect not only upon the organisms that produce them but also 

 upon other organisms ( lOi i ). The formation of an autolytic substance 

 by a thermophilic actinomyces was also demonstrated (492, 531). The 

 filtrates of such lysed cultures were said to offer promise in the treat- 

 ment of actinomycosis caused by Actinomyces bovis (185). 



In the case of some actinomycetes, like S. griseus, the lysis of the cells 

 appears to be a definite stage in the life cycle of the organism. This is 

 observed particularly in rapidly growing submerged cultures, especially 

 when they are inoculated not with fresh spores but with cell growth 

 previously obtained under submerged conditions. The production of 

 streptomycin is definitely associated with the lysis of the culture j when 

 lysis progresses, not only does streptomycin formation cease completely 

 but the substance already formed may be rapidly destroyed. 



Despite a seeming similarity in their growth characteristics, and de- 

 spite the fact that some investigators (356) assumed that all actinomy- 

 cetes are able to act as antagonists, it is now definitely established (534, 

 971, 974) that one is dealing here with highly specific types or strains. 

 Although many actinomycetes yield, either in the culture filtrate or in 

 the mycelium, an ether-soluble substance that has some bacteriostatic 

 activity, only certain species, such as S. antibioticusy are capable of pro- 

 ducing the typical actinomycin. 



Both the quantitative production of the substance and the presence of 

 other substances depend entirely upon the culture of the organism. One 

 is dealing here both with strain specificity and with species character- 

 istics. 



Strains can be isolated from antagonistic actinomycetes that are com- 

 pletely inactive. This phenomenon seems to be correlated with the 

 type of growth of the organism; nonsporulating strains of S. griseus, 

 for example, do not produce streptomycin. The formation of this anti- 

 biotic agent is associated definitely with the growth of certain sporulat- 

 ing strains of this organism (832). 



