286 



PHYSIOLOGY OF THE FUNGI 



the incidence of certain diseases may be decreased by adding certain 

 bacteria, actinomycetes, and fungi to soil. For references, see Grossbard 

 (1948), Henry (1931), Waksman (1937), and Anwar (1949). 



The influence of various soil-inhabiting organisms in decreasing infec- 

 tion of barley by Helminthos'porium sativum has been reported by Anwar 

 (1949). Figure 56 illustrates some of these results. It is by no means 

 certain that these effects were due to the antifungal substances produced 

 by the antagonistic organisms. 



Fig. 56. The effects of certain soil organisms on the pathonogcnicit}^ of Helmintho- 

 s'porium sativum on barley. Seedlings grown at 80°F. in steamed soil infested with: 

 A, no organisms; B, H. sativum and Bacillus subtilis: C, H. sativum and Penicillium sp. ; 

 D, H. sativum and Trichoderma lignorum: E, H. sativum. (Courtesy of Anwar, 

 Phytopathology 39: 1011, 1949.) 



The situation in soil is very complicated. Basic antibiotics such as 

 streptomycin are adsorbed on clay; acidic antibiotics like clavacin are 

 apparently held less firmly. Gottlieb and Siminoff (1950) are of the 

 opinion that competition is more of a factor than antibiotic action as the 

 cause of one organism inhibiting another in the soil. Thus, either As-per- 

 gillus clavatus or Streptomyces griseus inhibits the growth of Bacillus 

 suhtilis in soil. No difference was noted between a strain of S. griseus 

 which produced streptomycin and one which did not. 



Schatz and Hazen (1948) reported that 124 of the 243 soil Actiyiomyces 



