46 INTERRELATIONSHIPS AMONG MICROORGANISMS 



concluded that all phenomena of antagonism among microorganisms 



can be conveniently classified into four groups : 



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



tigators, only the inhibitive forms of antagonism (in vitro) may be 

 designated as true antagonisms; the in vivo forms w^ere designated 

 as phenomena of antibiosis. As pointed out above (p. 38), this 

 differentiation is no longer 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. 



Duclaux (212) 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 (541) 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 (620) 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 j upon the destruction of these by boiling, the 

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

 terial spores were once more able to germinate. Some of the toxic sub- 

 stances appeared to be thermostable (668). 



Fungi are capable of producing not only growth-inhibiting but also 

 growth-promoting substances. By means of certain procedures, it was 

 found possible to separate the two (690). The tendency of fungus 

 hyphae to turn away from the region in which other hyphae of the 

 same fungus were growing was explained as a negative reaction to 

 chemical substances produced by the growing fungus (306). This nega- 



