Bacterial Mefabolism 



73 



The existence of an unusual mechanism of glucose fer- 

 mentation in Leuconostoc was clearly established by the 

 tracer experiments of Gunsalus and Gibbs (8). The fer- 

 mentation of glucose-1-C^^ and glucose-3, 4-C^^ showed 

 (Figure 4) that the carbon dioxide originates from carbon 

 atom 1 of glucose, the methyl group of ethanol from carbon 

 2, and the carbinol group from carbon 3. The lactate car- 



I 



2 

 3 



4 



5 

 6 



C'-6LUC0SE LEUCONOSTOC YEAST 



•CHO 'COg 'CHa 



CHOH CHs CH2OH 



°CHOH ^ "CHaOH XOz 



°CHOH "COOH °C02 



CHOH CHOH CH2OH 



I I I 



CH2OH CH3 CH3 



FIGURE 4. Glucose Fermentation by Leuconostoc, after Gunsalus and 



Gibbs (7) 



bons, starting with the carboxyl group, are derived from 

 glucose carbon atoms 4, 5, and 6. These results showed the 

 expected lack of mixing of the carbon from the two ends of 

 the glucose molecule, and also established an unusual origin 

 for the carbon dioxide and ethanol. In alcoholic fermenta- 

 tion by yeast, carbon dioxide is derived from carbons 3 

 and 4 of glucose, and ethanol comes from carbons 1, 2, 5, 

 and 6. 



The experiments of DeMoss (2) with cell-free extracts of 

 Leuconostoc provide additional evidence of a new mech- 

 anism. These investigators found that the enzymes aldolase 

 and triose phosphate isomerase, which are essential to the 

 glycolytic mechanism, are not present in these bacteria. The 

 details of the mechanism of glucose breakdown by Leu- 

 conostoc have not yet been worked out, but there is con- 



