Total Synthesis of Acetate from CO2 V. Determination by Mass Analysis of the Different Types of Acetate Formed from 13CO2 by Heterotrophic Bacteria

摘要

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.