Carbon assimilation by Pseudomonas oxalaticus (OX 1). 1. Formate and carbon dioxide utilization during growth on formate

Abstract

KETO ACID PRODUCTION BY TISSUE CULTURE 623 3. In stationary conditions, the quantities of the three keto acids can be calculated from their radioactivities. These quantities are small and correspond to the lactic acid or carbon dioxide generated during a few minutes only. 4. The average amount of each keto acid within a cell increases in parallel with the supply of glucose, but the ratio of the three keto acids does not change appreciably. Thus the enzymes of the citric acid cycle can, to a large extent, cope with an increase in the supply of pyruvic acid. 5. Pyruvic acid diffuses, from both mesenchyma and tumour tissue, into the medium where it is aoted upon by lactic dehydrogenase. In the given conditions, the inverse Pasteur effect can partly be explained as being due to this reaction. 6. Oxaloacetic acid and ox-oxoglutaric acid diffs into the medium from tumour, but not from mesenchyma tissue. This loss is attributed to some malfunction of the mitochondria in tumour tissue. But it is shown that this malfunction need not express itself in any great increase of the ratio of pyruvic acid to oxaloacetic acid or at-oxoglutaric acid within the cells or any great decrease in the of rate respiration.

The Formation of Ribulose 1:5-Diphosphate Carboxylase by Growing Cultures of Athiorhodaceae

“…Its presence has since been shown either directly or indirectly in many autotrophic bacteria (Trudinger, 1956;Aubert, Milhaud & Millet, 1957;Vishniac & Santer, 1957;Bergmann, Towne & Burris, 1958;Kornberg, Collins & Bigley, 1960) as well as in Pseudomonas oxalaticus growing on formate (Quayle & Keech, 1959a, b). The operation of the reductive pentose cycle in photosynthetic bacteria was suggested originally by observations that 3-phosphoglyceric acid appeared as an early product of W O , fixation by Rhodospirillum rubrum and 32 G. Microb.…”

“…It is also formed adaptively by Pseudomonas oxalaticus in response to formate, which is assimilated via the reductive pentose pathway, but oxalate (which is assimilated by a different route) does not induce the enzyme (Quayle & Keech, 1959a, b ;. The carboxylase is also adaptive in algae and is found only in organisms grown in the light with CO, as carbon source (Fuller & Gibbs, 1959).…”

The Assimilation of 1-C compounds

“…formate-grown Pseudomonas oxalaticus. Isotopic work with whole cells and enzymic studies with cell-free extracts point to growth of this organism on formate as being a strictly autotrophic process in which the bulk of the carbon is assimilated by the ribulose diphosphate cycle of carbon dioxide fixation, the necessary energy being derived from oxidation of formate (Quayle & Keech, 1959a, b). It would appear to be energetically wasteful to assimilate carbon at the level of carbon dioxide and reduce it to the level of cellular material when the substrate itself presents the cell with reduced carbon.…”

The oxygen‐tolerant and NAD+‐dependent formate dehydrogenase from Rhodobacter capsulatus is able to catalyze the reduction of CO2 to formate

“…In organisms that catalyze the oxidation of formate, this reaction is a key process for obtaining energy and reducing equivalents. The CO 2 formed is usually incorporated predominantly into the ribulose 1,5-bisphosphate cycle, as in autotrophic organisms [9,10]. Metal-dependent FDHs from prokaryotic organisms are members of the dimethylsulfoxide family of mononuclear molybdenum-containing or tungsten-containing enzymes [1].…”