ACTION OF BACTERIA AGAINST FUNGI 153 



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 conjiuens in freshly 

 burned-over soils, but not in natural soils, was explained (684) 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 

 (883) 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 

 growth of fungi. The active substances produced by these organisms 

 show considerable selective action just as in the case of the bacteria. 

 Actinomycin was found (974) to inhibit the growth of Penicilliuniy 

 Aspergillus J Ceratosiomella, and yeasts in concentrations of i :50,000 j 

 larger amounts (1:10,000) were required to inhibit other fungi, in- 

 cluding Rhizofus and Trichoderma. Streptothricin is less effective 

 against fungi, although it inhibits the growth of certain yeasts (1031). 



In general, antibiotics vary as much in their antifungal as in their 

 antibacterial effects. Some, like gliotoxin and actinomycin, were found 

 to be highly active against both parasitic and saprophytic fungi, whereas 

 others, like chaetomin and streptomycin, had little if any activity. Since 

 some of the substances, like actinomycin, have a highly toxic effect 

 upon animal tissues, the selection of a suitable antifungal agent for 

 chemotherapeutic purposes is limited to a very few promising mate- 

 rials j among these gliotoxin and streptothricin were mentioned (771). 



