no ACTINOMYCETES AS ANTAGONISTS 



causing infections in man and other animals, and certain plant diseases 

 (potato scab, sweet potato pox) are caused by aerobic species of actino- 

 mycetes. 



ANTAGONISTIC PROPERTIES 



Many actinomycetes have the ability to antagonize the growth of 

 other microorganisms, notably bacteria, fungi, and other actinomycetes; 

 this is brought out in Tables 1 5 and 1 6. The antagonistic species are not 

 limited to any one genus but are found among three genera, Nocardiay 

 StreftomyceSy and Mkromonosfora, 



Gasperini (322) first demonstrated, in 1890, that certain species of 

 the genus Strepomyces had a marked lytic effect upon other micro- 

 organisms. He emphasized that "Streftothrix develops habitually in a 

 spontaneous manner upon the surface of bacteria and fungi, upon which 

 it lives to a limited extent in the form of a parasite, due to the faculty 

 that its mycelium possesses to digest the membrane from these lower 

 fungi." Greig-Smith (364, 365) found that soil actinomycetes are an- 

 tagonistic to not only bacteria but also certain fungi j since actinomy- 

 cetes grow abundantly in normal soils, it was suggested that they may 

 become an important factor in limiting bacterial development. Lieske 

 established (571) that specific actinomycetes are able to bring about 

 the lysis of many dead and living bacterial cells; they are selec- 

 tive in their action, affecting only certain bacteria such as S. aureus and 

 S. fyogenesy but not S. lutea, S. marcescens, or Ps. aeruginosa. 



Rosenthal (805) isolated from the air an actinomyces species which 

 he designated as the true biological antagonist of the diphtheria or- 

 ganism. He inoculated the surface of an agar plate with an emulsion of 

 the bacteria and inoculated the actinomyces into several spots. At the 

 end of two days, the plate was covered with the diphtheria organisms, 

 but the colonies of the actinomyces were surrounded by large trans- 

 parent zones. In another method utilized, agar was mixed with an emul- 

 sion of the diphtheria bacteria killed by heat, and the mixture was 

 poured into plates. After solidification of the medium, the antagonist 

 was inoculated in several spots on the plates. Its colonies gradually be- 

 came surrounded by clear zones, thus proving that it produced a lytic 



