VITAMIN-SYNTHESIZING DEFICIENCIES 21 



taining 50^ of pantothenate per liter after 50 hours. Read- 

 ings taken at 72 hours would be interpreted to mean that it was a 

 "nonsynthesizer." Culture No. 10 is capable of more rapid growth 

 than culture No. 3 in Burkholder's without added pantothenate. 

 Culture No. 10 grows much more slowly in the absence of panto- 

 thenate than in its presence. Culture No. 10 synthesizes panto- 

 thenate after a considerable lag in Burkholder's medium; in Hut- 

 ner's medium the lag is much shorter. Burkholder's medium is 

 a much better diagnostic medium than Hutner's, since growth oc- 

 curs more rapidly on it than on Hutner's when pantothenate is sup- 

 plied, but when pantothenate is not added growth occurs less rap- 

 idly on Burkholder's than on Hutner's. That is, Burkholder's is a 

 better medium when pantothenate is added and a poorer medium 

 without added pantothenate. 



Fig. 21-1 Comparison of the Amounts of Growth on Burk- 

 holder's and Hutner's media. The turbidity indicated by a Kiett 

 Photoelectric Colorimeter is plotted against the time in hours 

 after inoculation. Culture No." 3 was grown on two batches of 

 Hutner's medium, one containing 50 7 of pantothenate per liter 

 and the other containing no added pantothenate. It was also 

 grown on two different batches of Burkholder's medium, one con- 

 taining 50 7 per liter of pantothenate and one no added panto- 

 thenate. Culture No. 10 was also grown on these four different 

 kinds of media. 



THE 'VITAMIN'' PEDIGREE 



Table 20-2 (Chapter 20) describes the melibiose -fermenting 

 capacity of the various cultures which were subsequently investi- 

 gated in some detail for their "vitamin-synthesizing" activity on 

 Burkholder's medium according to his technique. The original 

 diploid culture of S. cerevisiae (No. 1) was incapable of ferment- 

 ing melibiose and its offspring, cultures Nos. 3, 4, 5 and 6 were 

 similarly incapable. In this pedigree the numbers are used to in- 

 dicate the different cultures produced by the four spores of a single 

 ascus. Thus cultures 3, 4, 5 and 6 were originally from one diploid 

 ascus of S. cerevisiae. Culture No. 2 (S. carlsbergensis) fermented 

 melibiose as did all its haploid progeny. Culture No. 7 was the only 

 survivor of a single ascus and a mating between it and No. 4 produced 

 a hybrid supposedly heterozygous for the ability to ferment melibiose. 



