THE METABOLISM OF LABELED GLUCOSE BY THE PROPIONIC ACID BACTERIA

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Abstract
Different types of labeled glucose (1-, 2-, 6-, and 3,4-labeled) were fermented by cell suspensions of 2 spp. of the genus Propionibacterium and distribution of the C14 in the products determined. The following observations were made: (1) No matter which C of the glucose is labeled, there is considerable activity in all positions of the products of fermentation. (2) The activity of CO2 from glucose-3,4-C14 is highest, but there is considerable activity in the CO2 from glucose-1-C14. There is much less activity in the CO2 from glucose-2-C14 and glucose-6-C14. (3) Acetate from both glucose-1-C14 and glucose-6-C14 has highest activity in the methyl group. However, acetate from glucose-6-C14 is less active than that from glucose-l-C14. (4) Acetate from glucose-2-C14 has the highest activity in the carboxyl group and activity increases with time of fermentation. (5) Acetate from glucose-3,4-C14 contains considerable activity. (6) Labeling of the 2- and 3- positions of propionate is approximately equal with all types of labeled glucose, and usually the activity is the same as that of the 2- and 3- positions of succinate. With glucose-2-C14 and culture 34W the 2- and 3- positions of propionate are more active than the 2- and 3- position of succinate. It thus appears unlikely that succinate is the sole precursor of propionate in this fermentation. A difference in the labeling of the carboxyl groups of succinate and propionate was observed with glucose-3,4-C14. It is proposed tentatively that the major part of the data can be explained on the basis of an Embden-Meyerhof type of cleavage of the glucose with a simultaneous second type of cleavage which is not yet identified.