AN'I'AdoMS'l'K" IM{(tlM:in"Ii:S 



209 



a ,iir(t\\ til siiimilanl. On the oilier Imiid, I's. 

 jii/oci/aiti IIS repressed the .u'rowtli n\' x.iiioiis 

 a('tiii()niyc(>t{>s in mixed eultuic, and cxcn 

 hrouiiht al)()iit destruction of tlie actino- 

 niyeetes. 'Ihe anta.iionist ie el'teets of actiiio- 

 inyeel(\s were ascril)ed hy Lieske to tlieir 

 al)ilit\- to e.\eri't(> toxic substances that ha\(' 

 till' capacity to inhibit the f^rowth of other 

 orti;aiiisnis oi' exiai to ilestroy them. 



M tiller (H)OS) first observed that certain 

 piij;meiit-i)ro(hiciiiij; streptomyces {S. cocli- 

 mlar) ari' able to suppress the (h^velopmeiit 

 of yeast-like fuiiiii. In a study of the assoei- 

 atix'e and antaii'onistie etfeets of certain 

 actinomycetes and fungi, Porter (1924) dem- 

 onstrated that several organisms now known 

 to belong to the genus Streptomyces, namel}' 

 »S. tricolor, S. albus var. ochraccus and S. 

 nigrificans, produced marked inhibitory ef- 

 fects upon the growth of fungi. He suggested 

 that such inhibitory action may aid in species 

 identification. 



Gratia (1924) definitel}^ established the 

 potentialities of actinomycetes as powerful 

 antimicrobial agents. He and his associates 

 isolated a preparation, designated "myco- 

 lysate," which was actually used in the treat- 

 ment of many clinical cases caused by 

 pathogenic bacteria, notably the typhoid 

 organism. 



Rosenthal isolated, in 1925, from dust, an 

 actinomycete which he designated as the 

 true biological antagonist of the diphtheria 

 bacillus. He inoculated the surface of an agar 

 plate with an emulsion of the bacillus and 

 then introduced the actinomycete culture 

 into several spots on the plate. After 2 days' 

 incubation, the actinomycete colonies were 

 surrounded by large transparent zones, 

 whereas the rest of the plate was covered 

 with the growth of the diphtheria organism. 

 When an emulsion of this organism, pre- 

 viously killed by heat, w'as mixed with agar, 

 and the mixture poured into the plates and 

 moculated with the actinomycete, the colo- 

 nies of the latter were surrounded bv clear 



zones. Tliis denionst latcd the fad that the 

 actinomycete produced a lytic substance; 

 which diffused through the agar and dis- 



sohcd I he (lend bactei'ial cells. 



r<)rc<><l Aiilii<;(>iiisin 



The nature of the ant imici-obial effects of 

 dilTer(>iit microbes is greatly influenced by 

 the energy and nitrogen sources in the me- 

 dium. Schiller belie\('d that antagonism 

 could be induced bv using microbes as nu- 

 trients: in a dilute glucose solution without 

 nitrogen, yeasts were said to be "forced" to 

 kill and digest bacteria; if the yeasts were 

 added to a full}^ developed bacterial culture, 

 a bacteriolytic substance was produced 

 which was also active outside of the yeast 

 cells. Howe^•er, when the bacteria were inoc- 

 ulated into cultures of yeasts suspended in 

 distilled water, the yeasts were killed. Vari- 

 ous efforts, however, to adapt cultures of 

 actinomycetes by the process of ''forced 

 antagonism" to grow on specific bacteria 

 failed to yield antibiotics that the organisms 

 w^ould not produce normally when grown 

 upon proper artificial media. 



The Soil as a Source of Antagonistic 

 Actinomycetes 



The soil may be considered as the major 

 source of antagonistic organisms, especially 

 actinomycetes. Extensive studies carried out 

 in our laboratories on the enrichment of soil 

 with .V. tuberculosis did not lead to any 

 special development of actinomycetes active 

 upon these organisms. This can he explained 

 by the fact that the production of antibiotics 

 by an organism does not take place in re- 

 sponse to certain specific nutrients. Thus, 

 the activity differs from enzymatic processes 

 that exhibit the phenomena of adaptation, 

 whereby the organism benefits directly from 

 a particular reaction. The activit}'- is differ- 

 ent, also, from that following soil enrichment 

 which results in the development of nitrify- 

 ing and nitrogen-fixing bacteria. The forma- 



