GENETICAL CHARACTERS 11-16 



Dr. Caroline Raut (unpublished) has found a difference in the 

 rate of hydrolysis of maltose and of alpha methyl glucoside by 

 enzyme preparations from* yeasts of the four different genotypes, 

 with high activity always associated with the dominant gene. 

 Therefore, it appears that there are two enzymes, one specific 

 for maltose and the other for alph:i methyl glucoside. 



VITAMIN, AMINO ACID, AND NUCLEIC ACID 

 COMPONENT DEFICIENCIES 



Yeasts differ in their ability to grow in synthetic medium in 

 the absence of different B vitamins, amino acids, and nucleic acid 

 components. We have found that in most instances prolonged in- 

 cubation of an apparently deficient culture has finally resulted in 

 full growth. This indicated that relative differences in capacity 

 for synthesis are encountered more frequently than absolute dif- 

 ferences. However, we have found single gene differences which 

 distinquish those which grow quickly and those which grow after 

 delay in deficient medium. The method for classifying yeasts 

 is to grow them in 18 x 100 mm. Kimble tubes which have been 

 acid cleaned and sterilized and filled with 15 cc. of Burkholder's 

 vitamin-free medium to which the various essential nutrilites have 

 been added (chapter 21). Deficient medium is prepared by elimi- 

 nating one of these substances. The amount of growth is determined 

 by inspecting the cultures in a Klett photoelectric colorimeter 

 using a green filter. The Klett instrument was rebuilt with a hole 

 to accomodate the large type test tube. By this method, it is pos- 

 sible to keep tubes under observation for more than a month. In- 

 oculation is made by preparing a dilute suspension of cells in dis- 

 tilled water and making inoculation with a loop containing a uniform 

 number of cells (300 to 1500) as indicated by control plates and 

 by direct coimts. 



The deficiencies are usually relative for the control test (with- 

 out the nutrilite) eventually achieves full growth. Therefore, it is 

 necessary to noake the photometric reading at an optimal time. The 

 time varies for different deficiencies. Cultures respectively de- 

 pendent and independent of paraminobenzoic acid show a maximum 

 difference on the second or third day after inoculation, but the de- 

 pendent cultures begin to grow rather well on the fourth day so 

 readings must be made before that time. Methionine and adenine 

 deficiencies can be diagnosed on the second or third day but not 

 on the fifth. Pyridoxine dependent and independent cultures can 

 be distinguished on the third or fourth day and the differences per- 

 sist for about two weeks. Pantothenate dependent cultures are dis- 

 tinguishable from independent cultures on about the fifth or sixth 

 day and the dependent cultures do not begin to grow until the third 

 week. 



