216 



THE ACTIXOMYCETES, Vol. I 



60- 



I 50- 



§ 



o 



<2 40 



u. 

 O 



30- 



UJ 



o 



< 



520- 



o 



a: 



UJ 



10- 



n % CAUSING SLIGHT INHIBITION 



^ % CAUSING STRONG INHIBITION 



^ % CAUSING VERY STRONG INHIBITION 



I TOTAL PERCENTAGE CAUSING INHIBITION 



I flI 



ij 



-60 



-50 



- 40 



-30 



• 20 



B. subtilis 



S. aureus 



P. vulgaris 



E. call 



P. aeruginosa 



BACTERIA AS TEST ORGANISMS 

 FuuRE 84. Degree of aiitil)iotic' UL'tivity with bacteria as test organis ms (Reproduced from: Emerson 

 R. L. et al. J. Bacteriol. 52: 362, 1946). 



been known. Major attention was directed 

 toward their activity upon plant pathogenic 

 fungi (Tins, 1932; McCormack, 1935). 

 Alexopoulos was the first to study, in 1941, 

 the distribution of antagonistic activities 

 among actinomycetes against fungi. Of 80 

 cultures tested against CoUetotrichum glocos- 

 porioicles, 17.5 per cent were strong inhibi- 

 tors, 38.8 per cent were weak inhibitors, and 

 43.7 per cent had no effect at all. Meredith 

 made a survey of the distribution of organ- 

 isms antagonistic to Fusan'um oxysporum 

 ciibense in Jamaica soils. The antagonists 

 were not evenly distributed, 10 of the 60 soil 

 samples giving 44 per cent of the antagonistic 

 organisms. Those actinomycetes that were 

 antagonistic to Fiisarium when grown in 

 their own soil-solution agar were not always 

 antagonistic when tested in soil-solution agar 

 prepared from another soil. A culture of an 

 jictinomycete isolated from a compost pro- 

 (hiccd lysis of the Fiisarium. When spores 

 of l)oth organisms were mixed in an agar 

 medium, the fungus de\eloped normally for 



2 days but began to undergo lysis on the 

 fifth day, large sections of the mycelium 

 disappearing. On the seventh day only 

 chlamydospores were ob.served. In 9 days 

 the fungus completely disappeared, whereas 

 the actinomycete was making a normal 

 growth. 



Leben and Keitt isolated a streptomyces 

 that was antagonistic to various phytopath- 

 ogenic fungi, but not to most bacteria. The 

 active material was heat-labile, soluble in 

 various organic .solvents, and in water at pH 

 9.3. It inhibited the growth of fungi and of 

 only very few bacteria. Of 3,788 actinomycete 

 cultiu'cs isolatetl from soil by Cooper and 

 Chilton and tested against Pythium, 896, or 

 23.() per cent, showed some antagonistic ef- 

 fect upon the fungus. Certain actinomycetes 

 were found to be responsibh^ for the destruc- 

 tion, in soil, especially in j)artly sterilized 

 soils, of the mycelium ofOpJuOboIus graminis, 

 tlie cause of the take-all disease of wheat. 

 The parasitizing and antibiotic effects of 

 actinomycetes and other soil organisms were 



