Waksman — 114 — Actinomycetes 



Leben and Keitt (254) isolated a culture of Streftoviyces which 

 was antagonistic to 29 phytopathogenic fungi, but not to most bacteria. 

 The culture was grown in corn-steep medium in shake flasks. The 

 culture filtrate was acidified to pH 2.5 and the acti\^e substance extracted 

 from the precipitate with ethanol. A preparation was obtained which 

 completely inhibited VenUiria inneqiialis in a 1:8,000,000 dilution and 

 Sclerotinia fructicola in a 1:11,000,000 dilution. The antibiotic is 

 water-insoluble. 



The above antibiotic was designated as antimvcin. It was purified 

 by extracting the precipitate produced on acidification of medium to 

 pH 2.5 with ethanol. The active material was heat-labile, soluble in 

 various organic solvents and in water at pH 9.3. The active substance 

 inhibited the growth of various fungi and of only very few bacteria 

 (255). Several entities were isolated from antimycin preparations and 

 designated as A, B and C. The A was a nitrogenous phenol (C2S- 

 H40O9N0). The substance inhibits the respiration of Saccharmnyces 

 cerevisiae, of cytochrome oxidase and succinic dehydrogenase. 



Actinomycetes also exert marked antagonistic effects against species 

 of Fythnini, as in the case of root rot of sugar cane. Of 3,788 cultures 

 isolated from soil and tested against a parasitic strain of Pythimn, 896 

 or 23.6 per cent showed some antagonistic effect upon the fungus, the 

 effect, in some cases, being marked. The occurrence of such antag- 

 onistic organisms and the extent of their activities were less pronounced 

 in heavy or infested soils than in light soils (79). 



Certain actinomvcetes were found (511a) to be responsible for the 

 destruction of the mycelium of Ophioholus graminis, the cause of the 

 take-all disease of wheat, in the soil, especially in partly sterilized soils. 

 This parasitizing and antibiotic effect of actinomycetes and of other soil 

 organisms is responsible for the check in the development of Ophiohohts 

 in natural soils. 



Actinomycetes possess antagonistic properties not only against bac- 

 teria and fungi but also against other actinomycetes (275). The more 

 aerobic species are antagonistic to the less aerobic types. Millard 

 (296) believed that he succeeded in controlling potato scab caused by 

 Streptomyces scabies by the use of green manures such as grass cuttings. 

 The development of scab on potatoes grown in sterilized soil and inocu- 

 lated with S. scahies was reduced by the simultaneous inoculation of the 

 soil with Streptomyces praecox, an obligate saproph\'te (299). By in- 

 creasing the proportion of the latter organism to the pathogen, the 

 degree of scabbing on the test potatoes was reduced from 100 per cent 

 to nil. The sterilized soil provided sufficient nutrients for development 

 of the antagonist, and only a small increase in the control was obtained 

 when grass cuttings were added and sterilized along with the soil. 



Sandford (379) was unable, however, to control potato scab by in- 

 oculation, with S. scahies and S. praecox, of either steam-sterilized or 

 natural soil containing different amounts of green plant materials. 



