Total Synthesis of Acetate from CO 2 V. Determination by Mass Analysis of the Different Types of Acetate Formed from 13 CO 2 by Heterotrophic Bacteria

Abstract

Mass analysis was used to determine the amount of acetate which is totally synthesized from ¹³CO₂ during fermentations by Clostridium formicoaceticum, C. acidiurici, C. cylindrosporum, Butyribacterium rettgeri, and Diplococcus glycinophilus. In the fermentation of fructose by C. formicoaceticum, 27% of the acetate was found to be totally synthesized from CO₂, and the remaining acetate was unlabeled, having been formed from fructose. Evidence is presented that the purine-fermenting organisms, C. acidiurici and C. cylindrosporum, totally synthesized about 9% of the acetate from CO₂, and that the methyl group of an additional 9% was formed from CO₂. The remaining acetate was formed from the carbons of the purine and not via CO₂. It has been postulated that the fermentation of the purines and synthesis of acetate from CO₂ both occur via derivatives of tetrahydrofolate. Evidence is presented that a compartmentalization of these folate intermediates is required if both the purine degradation and the CO₂ utilization involve identical intermediates. Neither B. rettgeri nor D. glycinophilus incorporated sufficient ¹³CO₂ into acetate to allow determination of the types of acetate by mass analysis, although they did incorporate labeled ¹⁴CO₂ in both positions of acetate.