330 



VITAMIN REQUIRKM I NTS 



1 — i — r 



5 10 



Time, days 



Figure I. The response of Phycomyces blakesleeanus to thiamine. Thiamine at 

 zero (curve 1), 0.2 (curve 2), and 1.0 (curve 3) m^M per 50 ml. From data of Dr. 

 Frederick Kavanagh. 



Cocarboxylase itself has been reported to replace thiamine (142, 256), 

 possibly entering the cell without dephosphorylation (231). 



Other metabolic functions of thiamine in fungi are suggested by the 

 sparing effect of oxaloacetate (13, 82) and the effect of thiamine in 

 promoting cytochrome synthesis by Ustilago sphaerogena (89). 



Free thiamine chloride hydrochloride has the structure: 



+ 



ci- 



Thiamine can be synthesized chemically by coupling the two moie- 

 ties, 2-methyl-5-bromomethyl-6-aminopyridine and 4-methyl-5-/?-hy- 

 droxyethylthiazole, commonly referred to as pyrimidine and thiazole, 

 respectively. Some microorganisms can use one or the other moiety by 

 itself to fill their thiamine requirement. The different types of fungi, 

 and some examples, are shown in Table 1 ; the most common require- 

 ment is for the pyrimidine moiety, i.e., most thiamine-deficient fungi 

 can synthesize thiazole and couple the two moieties to make the com- 

 plete molecule. Several studies have established that an organism able 



