Tracer Experiments on the Mechanism of Acetate Formation From Carbon Dioxide by Butyribacterium Rettgeri

Abstract

Butyribacterium retgri ferments glucose or lactate with the formation of acetate, butyrate, and carbon dioxide as the main catabolic products. The low yield of carbon dioxide and the high yield of fatty acids in the fermentation of lactate initially suggested that part of the acetate is derived from carbon dioxide (Barker and Haas, 1944). This conclusion was confirmed by tracer experiments. When lactate was fermented in the presence of C"4-labeled carbon dioxide, the resulting acetate was found to be radioactive with a carboxyl to methyl C'4 ratio of 1.33 (Barker et al., 1945). Comparison of the specific activities of the carbon dioxide and acetate indicated that at least one-fourth of the acetate is derived from carbon dioxide. Whereas the net yield of carbon dioxide is close to 0.4'mole per mole of lactate decomposed, the total carbon dioxide formation was estimated by application of the isotope dilution principle to be at least 0.8 mole per mole of lactate. The difference between the quantity of carbon dioxide formed and that which accumulated represents the quantity used for acetate synthesis. Several schemes have been suggested to explain the incorporation of carbon dioxide into both the methyl and carboxyl groups of acetate by B. retteri and other organisms (

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

“…"4CO, was incorporated into both carbons of acetate by all of the organisms: C. formicoaceticum and B. rettgeri fixed CO2 equally into both the methyl and carboxyl of acetate; C. acidiurici fixed 1.5-fold more in the methyl than in the carboxyl; C. cylindrosporum fixed over fivefold more in methyl than in the carboxyl; D. glycinophilus fixed almost eightfold more in the carboxyl than in the methyl of acetate. These data are in agreement with previously published results (1,5,8,19,24).…”

“…Lactate, the major product of the fermentation of glucose by B. rettgeri, becomes labeled in all three carbons in fermentations containing "4CO2 and has been postulated by Pine and Barker (24) (23). The specific radioactivity of the acetate was determined by total oxidation and analysis of the "4CO2 (37).…”

“…A number of anaerobic, heterotrophic bacteria have been described which are capable of fixing CO2 into both carbons of acetate. Included among these organisms are Clostridium aceticum (17,38), C. acidiurici (8), C. cylindrosporum (5), C. thermoaceticum (13), Butyribacterium rettgeri (24), Diplococcus glycinophilus (9), and C. formicoaceticum (1,12). The strain of C. formicoaceticum used in this work was isolated by El Ghazzawi (12).…”

“…from glucose was formed with incorporation of "4CO2 in all of its carbons, but the carboxyl carbon had a much higher radioactivity than carbons 2 or 3, which were of equal specific radioactivity. The two carbons of acetate were also equally labeled (24).…”

Single-carbon catabolism in acetogens: analysis of carbon flow in Acetobacterium woodii and Butyribacterium methylotrophicum by fermentation and 13C nuclear magnetic resonance measurement

“…In addition to CO and H2-CO2, methanol and formate serve as substrates for some acetogens (40). Butyribacterium rettgeri, now speciated as Eubacterium limosum (23), was shown in early studies to convert CO2 into both positions of acetate when grown on glucose (26), and later work by Hamlett and Blaylock (N. V. Hamlett and B. A. Blaylock, Bacteriol.…”