SPORE-FORMING BACTERIA 87 



cens are highly resistant. Ps. fluorescens produces a thermostable sub- 

 stance which is toxic to all bacteria except the green fluorescent forms 

 and which is active against actinomycetes but not against fungi. This 

 substance is water-soluble and dialyzable through collodion and other 

 membranes. 



In addition to the aforementioned bacteria, numerous other groups 

 were found to contain strains which had strong antagonistic properties 

 toward bacteria as well as fungi. Some of the antagonists were highly 

 specific, such as those acting upon the various types of pneumococcij 

 others were less selective, such as certain soil bacteria that can bring 

 about the lysis of living staphylococci and inhibit the growth of various 

 gram-positive and gram-negative bacteria. S. m,arcescens was antagonis- 

 tic to various spore-forming bacteria. These, in turn, were antagonistic 

 to sarcinae, bringing about their lysis, to V. comma, and to various 

 other bacteria. It was further found that the antagonists modified the 

 physiology of the antagonized organism. When two bacteria were 

 planted, for example, in the same medium, metabolic products were 

 formed that were not produced in the culture of either organism alone, 

 whereas certain decomposition processes were either hastened or re- 

 tarded (674). 



The various antagonistic bacteria can be divided into several groups, 

 on the basis of their morphological and physiological properties. 



SPORE-FORMING BACTERIA 



Many aerobic spore-forming bacteria possessing antagonistic proper- 

 ties have been isolated from a great variety of sources, such as soil, sew- 

 age, manure, and cheese. Among these, B. subiilis, B. mycoides, B. 

 mesenterkus, and B. brevis occupy a prominent place, as shown in 

 Table 10. 



Duclaux (212) isolated antagonistic spore- forming bacteria from 

 cantal cheese, the organisms having been designated as Tyrothrix. 

 Nicolle (680) obtained from the dust in Constantinople a strain of B. 

 subtilis that had decided bacteriolytic properties against members of the 

 pneumococcus group and various other bacteria such as the typhoid, an- 

 thrax, and Shiga organisms. E. coU and V. comma were most readily 



