BACTERIAL FERMENTATIONS 



strations of the phosphorylation of glucose by ATP (4) and the 

 conversion of glucose or fructose- 1,6-diphosphate to phospho- 

 glycerate by dried or toluene-treated cell suspensions (36), and 

 the conversion of phosphoglycerate to the normal fermentation 

 products by proliferating cells. More direct evidence for the 

 distinctive steps of the glycolytic pathway, the formation of 

 fructosediphosphate and its conversion to triose phosphate by 

 the aldolase reaction, is required, particularly in view of the 

 fact that all previous studies with propionic acid bacteria have 

 been done with crude enzyme preparations. Alternate inter- 

 pretations of the experimental data are therefore possible. For 

 example, the observation that toluene-treated cell suspensions 

 converted fructose- 1,6-diphosphate to phosphoglycerate in the 

 presence of fluoride and an oxidant, does not definitely establish 

 the existence of the aldolase reaction. An alternative inter- 

 pretation is that fructosediphosphate is converted to glucose-6- 

 phosphate which is oxidized to phosphoglycerate via phospho- 

 gluconate, pentose phosphates, and glyceraldehyde phosphate. 

 The recent tracer experiments of Leaver and Wood (17) 

 have demonstrated rather conclusively that the glycolytic path 

 is not the only mechanism of glucose fermentation by propionic 

 acid bacteria. The fermentation of glucose-l-C^'* gave carbon 

 dioxide with a higher specific activity than that of any carbon of 

 the other products. The quantitative data indicate that at least 

 20 per cent and possibly considerably more of the glucose is 

 decomposed by oxidation of carbon 1 to carbon dioxide, as 

 would occur in a nonglycolytic pathway. The fermentation of 

 glucose-3,4-C^^ resulted in the appearance of C^^in noncarboxyl 

 positions of acetate, propionate, and succinate. This result, 

 when considered in conjunction with other information concern- 

 ing the propionic acid fermentation, is inconsistent both with a 

 glycolytic pathway and with the Leuconostoc mesenteroides and 

 ribose phosphate pathways of glucose breakdown. The isotope 

 distribution data can be interpreted in terms of glucose oxidation 

 by the 2-keto-3-deoxy-6-phosphogluconate pathway of Pseudo- 

 monas saccharophila (20). However, no specific information is 



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