H. A. BARKER 



and 3, respectively, and the lactate carbons, starting with the 

 carboxyl group, from carbons 4, 5, and 6 of glucose. The 

 detailed mechanism of glucose fermentation by Leuconostoc has 

 not yet been worked out, but there is considerable evidence that 

 glucose-6-phosphate and 6-phosphogluconate are intermediates. 



The alcoholic fermentation of P. lindneri differs from that of 

 yeast in respect to the fate of the first three carbons of glucose 

 (13). Whereas in yeast glucose carbons 1 and 2 are converted 

 to ethanol and carbon 3 to carbon dioxide, in the P. lindneri 

 fermentation carbon 1 goes to carbon dioxide and carbons 2 

 and 3 to ethanol. The carbinol carbon of ethanol is derived 

 from carbon 2 of glucose, in contrast to the Leuconostoc fermenta- 

 tion in which the methyl carbon of ethanol comes from the 

 carbon 2 of glucose. The carbon distribution pattern of the P. 

 lindneri fermentation is sufficiently similar to that observed in 

 glucose oxidation by Pseudomonas saccharophila to suggest that the 

 underlying mechanisms of the two processes may be the same. 

 Glucose-6-phosphate, 6-phosphogluconate, and 2-keto, 3-deoxy, 

 6-phosphogluconate have been shown to be intermediates in 

 glucose breakdown by P. saccharophila (11,20). 



Two other fermentative bacteria that use nonglycolytic 

 mechanisms to some extent are Escherichia coli and Propioni- 

 bacterium pentosaceum. E. coli possesses enzymes catalyzing both 

 the glycolytic (10) and the nonglycolytic ribulose-phosphate 

 (29,31) mechanisms of glucose breakdown. The available 

 evidence indicates that the glycolytic path is used for anaerobic 

 decomposition of sugar, whereas both paths are used in the oxida- 

 tion of glucose. The experiments of Cohen (9) with glucose- 

 1-G^^ indicate that at least 14 to 37 per cent of the glucose 

 decomposed aerobically is metabolized via the pentose pathway. 

 The remainder of the glucose presumably is oxidized by the 

 glycolytic path, although specific and conclusive evidence for 

 this has not been obtained. 



Propionic acid bacteria probably use both glycolytic and 

 nonglycolytic pathways of glucose fermentation to a significant 

 extent. Evidence for the glycolytic pathway includes demon- 



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