82 BACTERIA AS ANTAGONISTS 



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, as in the case of those acting upon the various types of pneumo- 

 cocci (819, 821, 822) J others were less selective, as in the case of certain 

 soil bacteria that can bring about the lysis of living staphylococci and 

 inhibit the growth of various gram-positive and gram-negative bacteria 

 (820). S. marcescens was shown (61) to be antagonistic to B. subtilis, 

 B. mycoidesy and B. megatherium. These spore-formers, 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 modi- 

 fied 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 

 retarded (632). 



The various antagonistic bacteria can be divided into several groups, 

 on the basis of their morphological properties. 



SPORE-FORMING BACTERIA 



Many strains of aerobic spore-forming bacteria possessing antagonis- 

 tic properties and differing in morphological, cultural, and physiologi- 

 cal characteristics have been isolated from a great variety of sources, 

 such as soil, sewage, manure, and cheese. Among these bacteria, B. sub- 

 tilisy B. mycoides, B. mesentericus, and B. brevis occupy a prominent 

 place, as shown in Table 11. It was established (205) that some of 

 these bacteria produce in peptone media an alcohol-soluble, water- 

 insoluble substance endowed with bactericidal properties. 



Duclaux (208) was among the first to isolate and describe antagonis- 

 tic spore-forming bacteria. Cantal cheese was their origin, and the or- 

 ganisms were designated as Tyrothrix. NicoUe (640) isolated from the 

 dust in Constantinople a strain of B. subtilis that had decided bacterio- 



