SELECTED PAPERS 



It is extremely tempting, for instance, to try to establish a relation 

 between the quantitative values of the dissimilation reactions of the 

 various microbes and their characteristic assimilatory processes. 

 Should it not be possible that in this way one might learn to under- 

 stand why the butyric acid fermentation as dissimilatory process 

 enables the butyric acid bacteria to build up their proteins from am- 

 monia nitrogen, whereas the lactic acid fermentation does not permit 

 the lactic acid bacteria to accomplish this, though they can use pep- 

 tones for this purpose? It is evident that the caloric effects of the dissim- 

 ilation processes do not provide an adequate yardstick in this respect, 

 but that it is necessary to determine the free energy decrease of these 

 processes. It may be pointed out by the way that for this reason one 

 may easily conceive of the existence of organisms whose dissimilatory 

 reactions represent spontaneously occurring endothermic processes, 

 causing them, in contrast to all known organisms, not to produce 

 heat but rather to absorb this from their surroundings. 



Baron and Polanyi [191 3] have pointed out that in the case of re- 

 actions that proceed with a small caloric effect the decrease in free 

 energy by no means agrees with the caloric effect, whereas in oxida- 

 tive processes the discrepancy between the two is not very great. If 

 this be so, and if we must also conclude that the dissimilatory energy 

 conversions are used for assimilation, then we might expect that for 

 one and the same organism, or for closely related types, an identical 

 dissimilatory energy conversion should express itself in identical assim- 

 ilatory effects. The opportunity to check this is offered by the am- 

 monia- and nitrite-oxidizing bacteria, organisms with very similar 

 metabolic properties but which derive their energy from dissimilations 

 with different caloric effects. Now it is no doubt interesting that, 

 while the caloric effects of these reactions are 79 and 22, the ratios of 

 nitrogen oxidized to carbon assimilated by the two organisms are 35/1 

 and 135/1, respectively. This, therefore, agrees with the expectation 

 that they would be inversely proportional to the caloric effects. 



I have, however, lingered too long in discussing the energetic 

 unity in metabolism. It would please me if you had gained the im- 

 pression that the energetic approach may already open up some at- 

 tractive vistas, but that a closer investigation has hardly been begun 

 thus far. 



It is not only in energetic respect that we may discern a unity in 



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