192 



PHYSIOLOGY OF THE FUNGI 



have been reported to be less active or inhibitory. Whether ethyl thia- 

 mine occurs in nature is not known. The student is referred to Schopfer 

 (1943) for further information on thiamine specificity. 



Table 34. The Effect of Added Thiamine upon the Accumulation of Pyruvic 

 Acid in the Culture Filtrate of Fusarium lint Grown on Glucose- 

 Nitrate Medium 

 (Wirth and Nord, Arch. Biochem. 1, 1942. Published by permission of Academic 

 Press, Inc.) 



BIOTIN 



Biotin (vitamin H) was originally isolated as a grow^th factor for yeast. 

 It is known to be the factor which prevents raw-egg-white injury to 

 animals and is the respiratory coenzyme (coenzyme R) for species of 

 Rhizohium. Biotin is active at greater dilutions than are the other 

 vitamins. Pure biotin methyl ester was first isolated by Kogl and Tonnis 

 (1936) w^ho obtained 1.1 mg. of this substance from 250 kg. of dried duck 

 eggs. The structure of biotin was determined by Du Vigneaud et al. 

 (1942a) and confirmed by the synthesis of this compound (Harris et al., 

 1943). The structure of the biotin molecule is as follows: 



CO 



NH NH 



I I 



CH CH 



CH2 CH— (CH2)4— COOH 



\/ 



Biotin 



Some fungi deficient for biotin. Biotin deficiency appears to be 

 characteristic of most yeasts (Burkholder, 1943 ; Burkholder and Moyer, 

 1943; Leonian and Lilly, 1942). Numerous filamentous fungi have been 

 reported to be deficient for biotin, but this number is not so great as that 

 for thiamine. Frequently biotin deficiency accompanies thiamine 

 deficiency. 



