230 



PHYSIOLOGY OF THE FUNGI 



products antagonized the inhibitive action of sulfanilamide on the growth 

 of certain bacteria. Rubbo and Gillespie (1940) discovered that p-amino- 

 benzoic acid was a growth factor for certain bacteria. Woods (1940) 

 found that p-aminobenzoic acid in low concentration overcame sulfanila- 

 mide inhibition. A general theory was proposed by Fildes (1940) to 

 explain the antagonism between metabolites and compounds having 

 closely related structures. 



1400 



8 10 12 



Doys of incubotion 



16 



18 



20 



Fig. 48. The effect of various concentrations of sulfanilamide (amounts per flask) 

 upon the time of spore germination and upon the rate and amovnt of growth of 

 Aspergillus niger in flasks containing 55 ml. of sucrose— ammonium sulfate medium at 

 32°C. (Drawn from the data of Hartelius, Compt. rend. trav. lab. Carlsberg, S^r. 

 physiol. 24: 181, 1946.) 



Sulfanilamide was first considered to be antagonized by p-amino- 

 benzoic acid, rather than the reverse. This was due to the discovery 

 of the therapeutic value of sulfanilamide before it was known that 

 p-aminobenzoic acid was a vitamin. The structural relation between 

 these compounds has already been noted. The literature dealing with 

 the sulfonamides is abundant, but most of it relates to bacteria and 

 medicine. Relatively few papers have been published on the effects 

 of these compounds on the growth of fungi. 



Hartelius (1946) investigated the effect of sulfanilamide upon the 

 growth of Aspergillus niger and found that the amount of inhibition was 

 dependent upon the amount of inoculum used, the concentration of 

 sulfanilamide in the medium, and the time of incubation. The curves 

 in Fig. 48 illustrate the effect of time of incubation on inhibition, a factor 

 which is too often overlooked in experiments of this kind. The curves 



