ANTAGONISTIC INTERRELATIONSHIPS 47 



come antagonistic to E. coli or vice versa, depending on the initial num- 

 bers of the two groups, on the formation of metabolic products, or on 

 the exhaustion of nutrients (247). The toxic substances produced by 

 the antagonists comprise a variety of compounds, ranging from simple 

 organic acids and alcohols to highly complex bodies of protein or poly- 

 peptide nature. 



Various types of antagonism are recognized. Nakhimovskaia (627) 

 concluded that all phenomena of antagonism among microorganisms 

 can be conveniently classified into four groups of reactions: 



1. Antagonism in vivo vs. antagonism in vitro. According to some inves- 



tigators (513, 514), only the inhibitive forms of antagonism {in 

 vitro) may be designated as true antagonisms; the in vivo forms 

 were designated as phenomena of antibiosis. Usually, however, this 

 differentiation is not recognized. 



2. Repressive, bactericidal, and lytic forms of antagonism. One may fur- 



ther distinguish between bacteriostatic and bactericidal, fungistatic 

 and fungicidal forms of antagonism, as well as between antagonism 

 of function and antagonism of growth. 



3. Direct, indirect, and true antagonism. 



4. One-sided and two-sided antagonism; antagonism between strains of 



the same species and antagonism among strains of different species 

 (228). 



Duclaux (208) was the first to demonstrate that the growth of a 

 fungus upon a certain medium renders the medium unfavorable for the 

 further growth of the same organism. Kiister (509) has shown that 

 culture solutions in which fungi have grown are not suitable for the 

 germination of freshly inoculated spores but are improved by boiling. 

 This effect was observed as a result of the growth not only of the same 

 organism but also of other species. Similar observations were made for 

 bacteria: Marmorek (583) reported, in 1902, that the growth of 

 hemolytic streptococci in broth rendered the medium unsuitable for 

 subsequent growth of the same organism. The production of spores by 

 bacteria was believed to be caused by the formation of toxic, thermola- 

 bile organic substances; upon the destruction of these by boiling, the 

 rnedium was made again favorable for the growth of bacteria and bac- 

 terial spores were able to germinate again. Some of the toxic substances 



