208 



THi: ACTINOMVCETES, Vol. I 



Papacostas and Gate (1928) on "Microbial 

 associations and their therapeutic applica- 

 tion" and the more recent systematic work 

 of DuboR on tyrothricin. 



The fungi as producers of antibacterial 

 substances also received considerable atten- 

 tion (Waksman, 1945). The most spectacular 

 work was that on penicillin^ first recognized 

 by Fleming (1929), and finally established 

 by Chain, Florey, d al. (1940) as an impor- 

 tant chemotherapeutic agent. 



The actinomycetes were first recognized 

 by Oasperini (1890) as potential destroyers 

 of fungi and bacteria. Lieske reported, in 

 1921, that actinomycetes, especially the 

 aerobic, spore-forming types (streptomyces), 

 are not hindered in their growth by other 



organisms, but, on the contrary, are able, in 

 spite of their slow de^•elopment, to suppress 

 the growth of almost all bacteria and fungi. 

 This was foinid to be true on plates in which 

 actinomycetes were seeded after the growth 

 of fungi and bacteria had already occurred. 

 When a culture of an actinomycete and a 

 staphylococcus were mixed, streaked on agar 

 plates, and incubated at 37°C for 24 hours, 

 the plate became covered exclusively with the 

 growth of staphylococci; on further incuba- 

 tion, however, the actinomycete assumed 

 the upper hand and gradually replaced the 

 bacteria. The growth of the actinomycetes, 

 under these conditions, may have been bet- 

 ter than in pure culture, thus giving the im- 

 pression that the bacteria actually served as 



Fi(ii KK NO. Prnduclion of clear zones on l)acterial plates by antagonistic orjianisms 



