Nutrition 



123 



added thiamine may not be necessary for maintenance and for low-level 

 growth. Chilomonas Paramecium, for example, grows slowly in an acetate- 

 ammonia medium; addition of thiamine more than doubles the multiplication 

 rate, and addition of thiamine plus iron increases it by more than five times. ''** 

 It is, therefore, not indispensable in the diet for Chilomonas, but it is needed 

 for optimal growth. A number of versatile organisms— bacteria, mold, and 

 flagellates— can synthesize both the pyrimidine and the thiazole rings, and 

 from these the intact thiamine molecule (Table 23). Some require either the 

 pyrimidine or the thiazole from outside, others need both the pyrimidine and 



TABLE 23. REQUIREMENTS FOR THIAMINE AND ITS COMPONENTS 

 PYRIMIDINE AND THIAZOLE (MODIFIED FROM LWOFP') 



— indicates substance synthesized and not required in diet; 

 -f- indicates substance not synthesized and required in diet. 



the thiazole, and finally many Protozoa and some molds need the intact 

 thiamine molecule, as do all multicellular animals which have been investi- 

 gated (Table 23). Thiamine stimulates division of Tetrahymena but is not 

 a dietary requirement if D-amino acids are present in the medium. '^' '^ Table 

 23 shows that with increasing specialization among Protozoa the ability to 

 synthesize and to unite the two components drops out first, then the ability 

 to synthesize one or the other half, and finally the whole molecule is required 

 from outside. ^•^' ^^ 



Thiamine is required by all those insects and vertebrates which have been 

 tested. Mosquito larvae grown on foods in solution need thiamine, 0.0008 



