ACTION OF BACTERIA AGAINST FUNGI 



141 



the rust spores. The presence of these bacteria, however, Influenced the 

 nature of the germination of the spores, which gave rise to mycelium- 

 like forms with great numbers of copulating filaments, whereas in the 

 control cultures yeast-like forms prevailed and copulating cells were 

 rarely encountered. The presence of a certain concentration of bacterial 

 cell substance was essential to this antagonistic effect. With a more lim- 

 ited amount of cell material, the bacteria ceased to inhibit the germina- 

 tion of the spores but influenced the germination process in the same 

 manner as do nonantagonistic bacteria, that is, they stimulated the sex- 

 ual process. An increase in concentration of cell substance, even of non- 

 antagonistic organisms, would inhibit spore germination. 



The common occurrence of the fungus Pyronema confluens in freshly 

 burned-over soils, but not in natural soils, was explained ( 645 ) as due 

 to the destruction of the bacterial antagonists by heating of the soil. Ps. 

 fuorescens was particularly effective as an antagonizing agent. A com- 

 parative study of the fungistatic action of substances of bacterial origin 

 (855) has shown these to be more active than common disinfectants. 

 Tyrothricin inhibited the growth of animal pathogens in dilutions of 

 1:5,000 to 1:20,000, pyocyanin in 1:2,000 to 1:5,000, and hemi- 

 pyocyanin in i : 20,000 to i : 60,000. 



Actinomycetes may also exert a marked depressive effect upon the 



TABLE 31. FUNGISTATIC AND FUNGICIDAL ACTION OF ANTIBIOTIC 

 SUBSTANCES UPON CERATOSTOMELLA ULMI 



From Waksman and Bugie (928). 



