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 14C02 in both positions of acetate. I Present address:

Fermentation of Glucose, Fructose, and Xylose by Clostridium thermoaceticum : Effect of Metals on Growth Yield, Enzymes, and the Synthesis of Acetate from CO 2

“…It does not use hydrogen gas formation as an electron sink nor form butyric acid like many other clostridia. Instead, it has developed the ability to use CO2 as an electron acceptor, which is a property shared only with a few clostridia such as C. formicoaceticum, C. cylindrosporum, C. acidiurici (42), perhaps, C. tetani (4), and the methaneproducing bacteria (31,45,51).…”

“…The ability to synthesize acetate totallv from CO2 is not unique for C. thermoaceticum. With the use of 13CO2 and with mass analyses of the acetate formed, it has been established conclusively that C. formicoaceticum, C. acidiurici and C. cylindrosporum also synthesize acetate from CO2 (42). Of these organisms only C. formicoaceticum carries out a homoacetate fermentation.…”

Carbon Monoxide Oxidation by Clostridium thermoaceticum and Clostridium formicoaceticum

“…acidi-urici and C. cylindrosporum were grown on a bicarbonate-buffered hypoxanthine medium at 35°C. During growth on hypoxanthine the bacteria are known to synthesize acetate from CO2 (31). The cultures of the two bacteria did not oxidize carbon monoxide under the experimental conditions used at a concentration of either 0.2 or 5% in the gas phase; the concentration of carbon monoxide remained essentially constant from the beginning to the end of growth.…”

Net synthesis of acetate from CO2 by Eubacterium acidaminophilum through the glycine reductase pathway

“…In the present communication, we document that E. acidaminophilum can catalyze a net synthesis of acetate from CO 2 . Occurrence of this capacity among non-homoacetogenic bacteria has been documented before for Clostridium acidiurici and C. cylindrosporum [11], and for C. purinolyticum [12]. With that, the glycine pathway represents the third way through which acetate can be synthesized by anaerobic bacteria.…”

“…acetate formation from H 2 and CO 2 . The biochemical pathway used for glycine dismutation to CO 2 and acetate has been worked out in detail in the past [3], and is probably used as well in the reductive direction, as suggested before for some non-homoacetogenic clostridia [11,12]: CO 2 is reduced via formate, ATP-dependent linkage to tetrahydrofolate, and subsequent reduction to methylene tetrahydrofolate. The methylene derivative is reductively carboxylated and aminated to form glycine which is subsequently reduced to acetate, releasing ammonia.…”