BIOCHEMISTRY OF MICRO-ORGANISMS 



115 



The first important contribution to this 

 problem concerning the relationship be- 

 tween catabolism and anabolism was made 

 by Barker (1936), who showed that of a 

 number of simple oxidation substrates, 

 such as ethyl alcohol, glycerin, the lower 

 fatty acids, or glucose, only a small pro- 

 portion of each substrate is actually burned 

 to carbon dioxide and water by the color- 

 less alga Prototheca zopfii. Though con- 

 stant for each substance, this proportion 

 varied between about 20 and 50 per cent of 

 the total available carbon for different com- 

 pounds. The experimental results made it 

 seem probable that during the oxidation 

 of the substrate the remainder, comprising 

 80 to 50 per cent of the carbon, was con- 

 verted into some cell material of the ap- 

 proximate composition of a carbohydrate, 

 and possibly of the nature of a storage 

 product. 



Similar experiments with different Spi- 

 rillum species acting upon a variety of 

 simple respiration substrates soon led Gies- 

 berger (1936) to the conviction that this 

 phenomenon is far from rare ; that, in fact, 

 it might well turn out to be a generally 

 occurring phenomenon. Giesberger also 

 drew the conclusion that under normal 

 conditions and even with non-growing or- 

 ganisms assimilation is apparently insep- 

 arable from respiration, and that the pri- 



mary aim of respiration would be the 

 production of assimilatory substances; the 

 evolution of carbon dioxide during respira- 

 tion might thus be considered as an 

 accessory phenomenon and representing a 

 waste product of the main reaction. 



Clifton (1937) and Clifton and Logan 

 (1939) further extended these studies, first 

 by showing that the phenomenon in general 

 holds good for Pseudomonas calco-aceiica 

 and for Escherichia coli, and second by 

 demonstrating that substrates can be com- 

 pletely oxidized without the apparent for- 

 mation of assimilatory products in the 

 presence of certain poisons, particularly 

 a-dinitrophenol and sodium azide. The 

 work of Winzler and Baumberger (1938) 

 then established the same situation in the 

 case of yeast, that of Doudoroff^ for 

 strains of hydrogen-oxidizing bacteria. 

 Hence there seems to be very little doubt 

 that such syntheses as have been reported 

 here are very general in their occurrence. 



But the mechanism of this assimilation is 

 still largely unsolved; even the most im- 

 portant stages are a matter of speculation. 

 The different types of micro-organisms, 

 have yielded results which are far from 

 uniform. As an example, the following 

 tentative equations developed in the previ- 

 ously mentioned studies, may be presented : 



8 Unpublished results. 



Oxidation of Acetate 



Oxidation of Normal Butyrate 



