86 



BACTERIA AS ANTAGONISTS 



C orynehacterium difhtherlae. On agar plates the antagonist produced 

 a circular zone of inhibition, just beyond which was a ring of larger 

 colonies, indicating a stimulating effect. It was suggested that the an- 

 tagonist produced a toxin that was stimulating in small doses and in- 

 jurious in larger concentrations. The active substance was thermolabile 

 and nonfilterable. The antagonistic properties appeared to be inherent 

 in the particular strain of an organism and were not increased by serial 

 passage (1016). The action of filtrates of B. mesenterkus against diph- 

 theria organisms was considered (956) as highly specific. Other strains 

 of this organism were reported to be active against Pasteurella pestis 

 (246). Living gram-positive bacteria were found (768) to be more 

 susceptible than gram-negative organisms to the antagonistic action of 

 spore-forming aerobes j in the case of dead organisms, the reverse was 

 true. Plates were heavily seeded with the test bacteria and the centers 



TABLE 12. LYSIS OF PATHOGENIC BACTERIA BY VARIOUS STRAINS OF A 

 SPORE-FORMING ANTAGONIST (CYTOLYTICUS) 



