KLUYVER S CONTRIBUTIONS TO MICROBIOLOGY AND BIOCHEMISTRY 



been ineffective in promoting growth. And confronted with a nega- 

 tive result Kluyver may well have felt that it would be advisable not 

 to mention it in order not to introduce facts that could more easily 

 detract from the main point than help to explain it. This would have 

 been sound scientific strategy and prudence ; and Kluyver often made 

 use of it when experiments in his laboratory yielded results that ap- 

 peared to embarrass the orderly development of a particular investiga- 

 tion. The only experiments in which it was shown that the various 

 yeasts can grow abundantly at the expense of glucose pertain to yeast 

 extract media. These had also been found satisfactory by Rose and by 

 Lindner and Saito; but these authors had accounted for the good 

 growth of their yeasts in glucose-yeast extract solutions by invoking a 

 putative presence of glycogen in these media. Kluyver pointed out 

 that this explanation fails to account for the extremely poor develop- 

 ment of such yeasts in yeast extract without glucose, and thus con- 

 cluded that, in an otherwise appropriate medium glucose can be as- 

 similated as well as fermented. 



It may here be mentioned that this early encounter with conflicting 

 results depending on the use of pure or impure maltose preparations 

 later aided Kluyver and Hoogerheide in dispelling an apparent 

 anomaly in the behaviour of certain yeasts towards maltose under 

 aerobic and anaerobic conditions, respectively. When Trautwein and 

 Weigand had announced that S. marxianus and S. exiguus, although 

 unable to ferment maltose, could nevertheless oxidize this sugar, 

 Kluyver felt that this was incompatible with the views he had mean- 

 while developed concerning the relation between fermentative and 

 oxidative metabolism. Hence a re-investigation of the situation was 

 undertaken in collaboration with Hoogerheide [1933a]. From this it 

 appeared that the rate of oxygen utilization by these yeasts in maltose 

 solutions was dependent on the sugar concentration at levels far 

 exceeding those at which glucose shows a similar effect; that in 10 

 per cent maltose solutions the rate drops sharply after relatively short 

 periods of incubation during which the maltose concentration could 

 not have been lowered appreciably; and that a 10 per cent maltose 

 solution previously freed from fermentable monosaccharides by anaer- 

 obic incubation with a yeast that cannot ferment maltose no longer 

 causes an oxygen consumption noticeably in excess of that observed 

 in sugar-free suspensions of the two yeasts. 



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