BIOGRAPHICAL MEMORANDA 



possessed an exceptionally high affinity for hydrogen, which was equiv- 

 alent to having a high oxidative capacity, a supposition that was fur- 

 ther supported by the fact that they did not produce acid from glucose, 

 apparently causing a complete oxidation of this substrate without the 

 temporary accumulation of incomplete oxidation products. These or- 

 ganisms, for obvious reasons, became known as Acetobacter peroxydans. 



The studies on the acetic acid bacteria had therefore shown that 

 biochemical properties could be advantageously used for the sub- 

 division of a genus already partially characterized on the basis of 

 physiological criteria. Hence it is understandable that, when the 

 fundamental principles of biochemistry had begun to emerge, Kluy- 

 ver expected that they would be even more efficaceous for the clas- 

 sification of micro-organisms in a still larger framework, promising 

 that ultimately such a classification might become based on numer- 

 ically determinable differences in the affinity of the protoplasm of 

 various microbes for hydrogen. Pending the establishment of appro- 

 priate methods for the quantitative evaluation of this property, one 

 could begin by using in its place the general metabolic patterns of the 

 organisms which could be ascertained by relatively simple analytical 

 procedures. 



This meant that biochemical characteristics far more fundamental 

 than, for example, the ability to ferment one or more particular sugars, 

 would come to serve as the basis for the creation of physiologically 

 homogeneous entities, comparable in many respects with Cohn's 

 'form genera'. It remained to develop a scheme in which the old form 

 genera and the new physiological groups could be combined, so that 

 satisfactorily circumscribed genera would ensue. That morphological 

 and physiological features could be conveniently merged had already 

 been shown by Donker's analysis of the fermentation pattern of Bac. 

 polymyxa which had indicated the striking similarity in physiological 

 respect of this morphologically typical sporeformer and the non- 

 sporeforming Aerobacter species. By proposing the new genus, Aero- 

 bacillus, for the former, the feasibility of this kind of approach had 

 been sufficiently demonstrated. 



Meanwhile the study of the propionic acid bacteria in Kluyver's 

 laboratory had shown that these organisms represent a remarkably 

 homogeneous group with respect to both their general morphological 

 and biochemical properties. This justified the resurrection of Orla- 



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