104 ACTINOMYCETES AS ANTAGONISTS 



ANTAGONISTIC PROPERTIES 



Many actinomycetes have the ability to antagonize the growth of 

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

 this is brought out in Tables 1 6 and 1 7. The antagonistic species are not 

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

 StreftomyceSy and Micromonosfora. 



Gasperini (317) first demonstrated, in 1890, that certain species of 

 the genus Streftomyces 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 (360, 361) found that soil actinomycetes are able 

 to antagonize 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 limiting bacterial development. Lieske 

 (527) demonstrated that specific actinomycetes are able to bring about 

 the lysis of many dead and living bacterial cells j they are selective in 

 their action, affecting only certain bacteria such as S. aureus and S. -pyo- 

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



Rosenthal (767) 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 

 substance that diffused through the agar and dissolved the diphtheria 

 cells. 



Gratia and Dath (350) suspended dead cells of staphylococci and 

 other bacteria in 2 per cent agar and exposed the plates to the air. A cul- 



