THE ACETIC ACID BACTERIA 23 



scheme except phosphofructokinase may also be used by 

 either the pentose cycle or the Entner-Doudoroff pathway. 

 The isotope data of Kitos et al. (23) argue strongly 

 against the use of glycolysis in whole A. suboxydans cells. 

 Likewise, when extracts are employed to oxidize glucose or 

 glycerol, the pentose cycle prevails (no acetate is formed 

 unless lactate or pyruvate is added). However, when the 

 cell-free extract is treated with Dowex-50 to remove Mg, 

 DPT, and pyridine nucleotides, it becomes possible to show 

 fructose diphosphate disappearance in a DPN-dependent 

 reaction, and the accumulation of 3-hour stable phosphate, 

 suggestive of 3-PGA formation. Both aldolase and triose 

 phosphate dehydrogenase are active under these conditions 

 (43). It thus appears that at least some of the reactions 

 of glycolysis can function in the traditional manner when 

 external conditions permit (or force?) their operation. The 

 importance of Mg in this test is clearly evident; in its pres- 

 ence the pentose cycle is favored to the virtual exclusion of 

 glycolysis. 



THE BIOSYNTHESIS OF AMINO ACIDS 



The foregoing sections on acetate non-utilization and lack 

 of a citric acid cycle logically raise the question of the ori- 

 gin of amino acids that normally arise from the cycle, espe- 

 cially glutamate and aspartate. These reactions are under 

 study, although at present the crucial experiments remain 

 to be carried out. Several bits of information are known 

 —for example, that this organism has great synthetic powers, 

 requiring [in contrast to the findings from an earlier study 

 (44)] only serine plus either glutamate, histidine, or pro- 



