KLUYVER'S CONTRIBUTION'S TO MICROBIOLOGY AND BIOCHEMISTRY 



behaviour. Whereas S. cerevisiae, isolated from the baker's yeast mar- 

 keted by the Netherlands' Yeast and Alcohol Manufactory, produced 

 a crop of about 60 mg dry weight per 50 ml of Hayduck's medium 

 with glucose, several other yeasts grew to the extent of only 1-8 mg, 

 although they yielded crops of 20-70 mg in maltose media. But these 

 results were not considered sufficient by Kluyver to accept Lindner's 

 interpretation based on a differential assimilation of glucose and mal- 

 tose ; he looked for and finally found an explanation that did not con- 

 travene the prevailing and generally fruitful notions on sugar metab- 

 olism. The starting point was Kluyver s familiarity with the investiga- 

 tions of Bertrand on the often startling effects of minute amounts of 

 certain substances on the development of diverse micro-organisms. This 

 led Kluyver to consider the possibility that impurities in the maltose, 

 rather than the sugar itself, might have been responsible for the good 

 growth of yeasts that failed to develop in glucose media. The validity 

 of this hypothesis was substantiated by experiments with carefully 

 purified maltose; when this was used as a substrate it proved to be as 

 ineffective as glucose for growth of the yeasts. 



During the recrystallization of the maltose from 80 per cent alcohol 

 Kluyver noticed the appearance, of a flocculent precipitate; thus it 

 became likely that it might have been this material that was respon- 

 sible for the profuse growth of various yeasts in the maltose-contain- 

 ing media. Nitrogen determinations carried out with the original 

 maltose, a Kahlbaum C.P. product, confirmed the presence of con- 

 siderable amounts of impurities, indicating as much as 0.22 per cent 

 'protein'. Kluyver assumed that this would have been introduced with 

 the amylase, presumably used in the manufacture of the maltose, and 

 that the 'protein' was required for the growth of certain yeasts in the 

 asparagine medium. He keenly realized that this should not be inter- 

 preted to mean that asparagine is inadequate as a general nitrogen 

 source, and pointed out that 'it is readily conceivable that asparagine 

 is unsuitable for the synthesis of particular cellular constituents, such 

 as nucleic acids, for which the nitrogenous impurity can be used . . . 

 even though asparagine may suffice for the synthesis of various other 

 nitrogenous cell materials'. 



In principle this interpretation is, of course, the one currently used 

 to explain the need for specific growth factors by diverse organisms, 

 and it is highly probable that the phenomenon Kluyver had here 



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