ACTION AGAINST PLANT DISEASES 121 



The formation of an autolytic substance by a thermophilic actinomyces 

 was also demonstrated (477, 502). The filtrates of such lysed cultures 

 were said to offer promise in the treatment of actinomycosis caused by 

 Actinomyces bovis (175). 



Despite a seeming similarity in their growth characteristics, and de- 

 spite the fact that some investigators (349, 973) assumed that all ac- 

 tinomycetes are able to act as antagonists, it is now definitely established 

 (504, 945) that one is dealing here with highly specific types or even 

 strains. For example, an examination of many species for an active sub- 

 stance similar to actinomycin brought out the fact that only S. antibioti- 

 cus was capable of producing this substance. Although many other 

 forms yielded an ether-soluble substance that had some bacteriostatic 

 activity, it could not be compared in chemical nature and in biological 

 action with actinomycin (944, 946). 



ANTAGONISTIC EFFECTS OF ACTI N O M YCETES 



AGAINST AGENTS PRODUCING 



PLANT DISEASES 



Various species of Streftomyces are also strongly antagonistic against 

 bacteria causing plant diseases, such as Bacterium solanacearum (414). 

 According to McCormack (552), aerobic conditions are necessary for 

 the development of the antagonistic properties of actinomycetes j those 

 requiring less oxidized conditions are themselves antagonized. B. mega- 

 theriumy for example, was said to be antagonistic to certain species but 

 was antagonized by others. Ps. fluorescenSy however, was antagonistic 

 to actinomycetes as a whole, causing their lysis. 



Actinomycetes possess antagonistic properties not only against bac- 

 teria but also against other actinomycetes (552), The more aerobic spe- 

 cies are antagonistic to the less aerobic types. Millard (604) believed 

 that he succeeded in controlling potato scab caused by Streftomyces 

 scabies by the use of green manures such as grass cuttings. The develop- 

 ment of scab on potatoes grown in sterilized soil and inoculated with 

 S. scabies was reduced by the simultaneous inoculation of the soil with 

 Streftomyces fraecoXy an obligate saprophyte ( 605 ) . By increasing the 

 proportion of the latter organism to the pathogen, the degree of scab- 



