AN'iwcoMS'i'ic iM{()iM:iri'ii;s 



217 



l)('li('\('(l l(» l)t> rcspoiisiMc I'oi' the check in 

 t lu'dcxclopiiHMil (i| I lie < )i)h /III Kilns in nat iiral 

 soils. 



Stoss(>l studicMl the (list riluil ion in soil of 

 act iiioniycet(>s acti\"e aj^ainsi |)athoi;(Miic 

 fungi. Dilutions of soil samples wei'e added 

 to suitable ai2;ar media, so as to ])eiinit 'M) 

 to ")() colonies to de\-elop on each plate. The 

 phites wore incubated for 4 days at 2()°C\ 

 Suspensions of spores of four nuitually non- 

 antajionistic phytojiathog-enic fungi were 

 tluMi spi-ay(Hl on the plates. After 2 days' 

 further incubation, 170 cultures of actino- 

 mycetes producing marked inhil)ition zones 

 against all the test fungi were isolated. Plate 

 cultures of the isolates were sprayed again 

 but with separate suspensions of eight fungi 

 and two bacteria. Twenty-one cultures, 

 mostly actinomycetes, were selected on the 

 basis of comparative inhibition. These or- 

 ganisms were grown in fi\'e liquid media in 

 shaken flasks. The culture filtrates were 

 tested for activity against Glomcrella cingn- 

 lata, by the use of a modified cylinder plate 

 method. Sixteen cultures produced an anti- 

 biotic in one or more media. Of the 170 

 organisms originally isolated, five appeared 

 to produce desirable substances, as deter- 

 mined by the above screening tests. Further 

 studies on the antagonistic effects of actino- 

 mycetes upon plant pathogenic fungi have 

 been made by ]\Iukherjee and Xandi (1955) 

 and others. Some actinom3xetes are particu- 

 larly active against yeasts (Takahashi, 1952). 

 The activities of soil actinomycetes upon 

 fungi pathogenic to man were examined b}- 

 Schatz and Hazen. 



Pridham ct al. (195G) made an extensive 

 survey of actinomj^cetes, largely strepto- 

 myces strains, for their growth-inhibiting 

 effect against phytopathogenic bacteria and 

 fungi. About 500 pure cultures were sub- 

 jected to primary screening by three meth- 

 ods against a minimum of 12 test organisms. 

 Based on their antimicrobial spectra, some 



200 strains were selected as warranting fur- 

 ther study and wei'c grown in a \ariety of 

 media in shake-flasks, llw cultinc filtrates 

 wei'e tested for antibiotic actixity 1)\' paper- 

 disc assay against nine organisms. Fifty-two 

 of th(> 200 strains sIiowcmI pi'omise. Culture 

 lilti'ates from eight sti-ains as well as two 

 substances isolated from the mycelium of 

 dil'fei-ent strains were then tested in the 

 greenhouse against certain plant diseases. 

 Xin(> of tlie 10 preparations showed broad 

 antifungal spectra in laboratory tests and 

 activity against at least one disease in green- 

 house tests. Phytotoxic effects were observed 

 with some of the test materials. The details 

 of the test are brought out in Table 57. 



Correlation of Antimicrobial Activity 

 and Pigmentation 



von Plotho correlated pigment production 

 by actinomycetes with their antagonistic 

 properties. Two hundred and ninety-one cul- 

 tures grown in colorless media were classi- 

 fied into four groups on the basis of pigments 

 produced either in the mycelium or in the 

 medium. Activity was determined by testing 

 against M ijcobacterium eos. Of the 61 cultures 

 (21 per cent) showing activity, 21 were in 

 the colorless group, 20 were in the red-yellow, 

 12 in the red-blue, and 8 in the red-brown 

 group. By using media in which pigments 

 could be seen readil}^, investigators might 

 well try such a correlation to learn whether 

 particular groups could be eliminated with- 

 out further testing. A detailed analysis of the 

 antibiotic pigments of actinomycetes was 

 presented in Chapter 13. 



Screening for Specijic Antibiotic- 

 yroducing Organisms 



By using the techniciue reported by Waks- 

 man, Reilly, and Johnstone (19-46) of adding 

 a particular antibiotic to the medium before 

 plating out soil samples, Umezawa et al. 

 (1949) were able to demonstrate the presence 



