UNITY AND DIVERSITY IN THE METABOLISM OF MICRO-ORGANISMS 



induce the oxidative degradation of the sugar by the body cells?* I 

 gladly leave the answer to these questions to those more competent; 

 but I believe that it was not unwarranted to pose them here, partic- 

 ularly because there is an ever-increasing amount of evidence in 

 favour of a fundamental unity in the mechanism of biological oxida- 

 tions that extends to everything that lives aerobically; a final example 

 may suffice to illustrate this. 



It has long been known that rancid coconut oil contains, among 

 other substances, various ketones, such as methyl nonyl ketone, methyl 

 heptyl ketone, etc. Dr. Derx has recently called my attention to in- 

 vestigations by Stokoe [1922] and by himself, demonstrating that these 

 substances originate under the influence of moulds which apparently 

 produce them by an incomplete oxidation of the fatty acids formed 

 from the oil. Now it is certainly most striking that these microbes 

 effect an incomplete oxidation of, e.g., lauric acid with the formation 

 of methyl nonyl ketone, in complete agreement with Knoop's theory 

 of fatty acid oxidation by higher organisms, according to which the 

 biological oxidation of fatty acids is initiated at the ^-carbon atom, 

 thereby producing /5-keto acids from which ketones are formed by 

 decarboxylation, a type of conversion that, in the body of the diabet- 

 ic, causes the production of compounds such as acetoacetic acid and 

 acetone. And many other arguments could be advanced in support of 

 the thesis that the mechanism of oxidative dissimilatory processes re- 

 veals a high degree of unity. 



It seems to be a practicable task to determine the successive inter- 

 mediate oxidation stages of physiologically important compounds 

 such as glucose, glycerol, etc., with numerous micro-organisms that 

 exhibit a low oxidative capacity. At the same time one may attempt 

 to ascertain in a quantitative manner the ease with which the various 

 steps are accomplished. It is hardly doubtful that such investigations 

 will increase our comprehension of the nature of microbial metabolism. 

 But by virtue of the above-mentioned unity it will also be eminently 



* Even if one had to assume that the oxidation of glucose proceeds by the round- 

 about way of glycogen, lactacidogen, and lactic acid - as has been proved for the 

 transformations during muscle contraction by the investigations of Embden, Meyer- 

 hof, Laquer, and others - similar considerations would nevertheless apply to the 

 later oxidative phases of this process. See the reviews by F. Laquer, 'Insulin', Natur- 

 wiss., 12, 89, 1924, and by O. Meyerhof, 'Die Energieumwandlungen im Muskel', 

 Naturwiss., 12, 181, 1924. 



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