198 PHYSIOLOGY OF THE FUNGI 



shown to require such growth factors, it is possible that some do exist. 

 Such requirements may be found among the artificially induced mutants. 



PANTOTHENIC ACID 



Pantothenic acid was first discovered (Williams et al., 1932) as a growth 

 factor for the Gebriide Mayer strain of Saccharomyces cerevisiae. The 

 isolation, identification, and synthesis of this compound was complete by 

 1940. It was later shown to be a vitamin for animals. Pantothenic 

 acid consists of two moieties joined together by means of an amide link- 

 age. The chemical formula for this vitamin is given below: 



CH3 



I 

 HO— CH2— C— CHOH— CO— NH— CH2— CH2— COOH 



I 

 CH3 



Pantothenic acid 



Pantothenic acid may be hydrolyzed to form /3-alanine (jS-amino- 

 propionic acid), the formula of which is H2N — CH2 — CH2 — COOH, and 

 a,7-dihydroxy-/3,;5-dimethylbutyric acid, a substituted butyric acid that 

 forms a lactone by elimination of one molecule of w^ater between the 

 carboxyl and the gamma hydroxyl (pantoyl lactone). Pantothenic acid 

 is thus analogous to thiamine, in that the molecule may be split into two 

 moieties. We might expect to find different pantothenic acid-deficient 

 organisms which require the intact molecule or one or both moieties. It 

 was found that the Gebriide Mayer strain of Saccharomyces cerevisae was 

 stimulated by /3-alanine and that this yeast completed the synthesis of 

 pantothenic acid when furnished with )8-alanine in the medium (Wein- 

 stock et al., 1939). Most yeasts deficient for pantothenic acid are unable 

 to synthesize the j8-alanine moiety of this vitamin. In general, this 

 moiety is not used so efficiently as pantothenic acid, and more than an 

 equivalent amount is required to support the same amount of growth. 

 The composition of the medium affects utilization, since, in the presence 

 of sufficient asparagine, /3-alanine is not utilized (Atkin et al., 1944). 



So far as is known, none of the fungi require pantoyl lactone as a growth 

 factor, but this compound was found (Ryan et al., 1945) to replace panto- 

 thenic acid for Clostridium septicum. It was shown by microbiological 

 tests that this bacterium completed the synthesis of pantothenic acid. 



Fungi deficient for pantothenic acid. Of the 10 strains of Saccharo- 

 myces cerevisiae tested for vitamin deficiencies by Leonian and Lilly 

 (1942), 9 w^ere highly deficient for this vitamin. Burkholder (1943) found 

 14 of the 38 species and strains tested to be deficient for pantothenic acid, 

 9 of these being species of Saccharomyces. It appears that deficiency 

 for this vitamin is more common in Saccharomyces than in other genera 

 of yeasts. Varying degrees of pantothenic acid deficiency were found in 



