ADAPTATION TO PANTOTHENATE DEFICIENCY 



22-34 



Fig. 22-9 A Week's Growth of Cultures 2154 and Adapted 2154 on 

 a Complete Medium Agar Plate Showing the Difference in rates of Growth, 

 The small colonies on the upper half of the plate are adapted 2154 and 

 the larger ones on the lower half are 2154, 



trations, in addition to the total cell number being reduced, the cells 

 are much smaller, are irregularly shaped, and tend to clump. (2) 

 The sick dependent cells may produce inhibitory metabolic products 

 in unusually high amount. Either exhaustion of the medium or ac- 

 cumulation of by-products by the unadapted cells would inhibit 

 growth of the adapted cells and thus account for the fact that maxi- 

 mum growth of mixed cultures is not obtained. 



However, at 27 and 07 levels, very little growth of non-syn- 

 thesizing cells can take place, so the adapted cells attain approxi- 

 mately the maximum amount of growth. There appears to be slight 

 inhibition of adapted cells even at 27. 



To test these possibilities, culture 2154 was allowed to grow up 

 completion in duplicate tubes of medium containing 207 and 107 of 

 pantothenate. A small inoculum of adapted 2 154 cells was then in- 

 troduced into the cultures grown at both concentrations and the same 

 inoculum plus sugar into the duplicates of the two cultures. There 

 was no further growth in the first case. When sugar as well as 

 adapted cells was added, there was a small increase in growth. 

 Since no growth at all was obtained when only adapted cells were 



