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 13 CO 2 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 CO 2 , 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 CO 2 , and that the methyl group of an additional 9% was formed from CO 2 . The remaining acetate was formed from the carbons of the purine and not via CO 2 . It has been postulated that the fermentation of the purines and synthesis of acetate from CO 2 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 CO 2 utilization involve identical intermediates. Neither B. rettgeri nor D. glycinophilus incorporated sufficient 13 CO 2 into acetate to allow determination of the types of acetate by mass analysis, although they did incorporate labeled 14 CO 2 in both positions of acetate.