222 



THE ACTINOMYCETES, Vol. I 



fetched. Such assumptions have been made, 

 for example, for the ehmination of typhus 

 abdominahs bacteria in irrigated soils, 

 merely because several streptomyces have 

 been isolated from such soils. 



Soil Enrichment with Pathogenic Or- 

 ganisms 



Soil enrichment with various chemical 

 compounds results in the isolation of organ- 

 isms capable of bringing about certain spe- 

 cific reactions. This is true, for example, of 

 the development of organisms capable of de- 

 composing cellulose or pectin by the addi- 

 tion of these substances to the soil; it is also 

 true for the enrichment of soil with sub- 

 stances like sulfur and ammonia to en- 

 courage the development in the soil of sulfur- 

 oxidizing and nitrifying bacteria. It was at 



first believed that the same principle would 

 apply to the isolation of antibiotic-producing 

 organisms. Claims were actually made that 

 favorable results were obtained. But the in- 

 troduction into the soil of cultures of micro- 

 organisms led to their destruction (Katznel- 

 son, 1940). 



Waksman and Woodruff (1940) attempted 

 to encourage by soil enrichment the develop- 

 ment of antibiotic-producing actinomycetes. 

 They at first believed this had succeeded. 

 They said that the survival of bacteria added 

 to the soil, but not indigenous to it, resulted 

 in the rapid dying out of such added bac- 

 teria. This was believed to have been accom- 

 panied by an increase in the numbers of soil 

 bacteria and actinomycetes capable of de- 

 veloping on the plate. On further additions 

 of cultures of bacteria to the soil, more rapid 



Table 58 

 Growth inhibition of streptomyces by their respective antibiotics (Waksman, Reilly, and Johnstone) 



Nature 

 of antibiotic 



Dilution units per mg, 



Actinomycin 



Streptothricin 



Streptomycin 



* S. liitea units; crystalline material. 

 t E. coli units; crude preparations. 



Table 59 



Cross-resistance among different streptomyces 

 (Krassilnikov) 



destruction of the added organisms resulted. 

 The nature of the antagonists developing in 

 the soil depended upon the bacteria added, 

 the soil treatment, and the temperature of 

 incubation. Several antagonists were isolated 

 from the soil. Sterile culture filtrates of these 

 antagonists were capable of reducing con- 

 siderably the numbers of bacteria and ac- 

 tinomycetes in the soil. A highly active sub- 

 stance was obtained from a soil actinomycete. 

 Further studies (Waksman and Schatz, 

 194()), however, on the enrichment of soil 

 with suspensions of living gram-negative bac- 

 teria and witli both living and dead tubercu- 

 losis organisms resulted in comph^te failure 



