β Scribed by Clayton, Roderick K. ;Dettmer, Franz H. ;Robertson, Arthur E.
No coin nor oath required. For personal study only.
With 1 figure in the text (Eingegangen am 29. September 1956) i n an earlier p a p e r (CLAYTO~ et at., 1956) it Was r e p o r t e d t h a t the oxidative m e t a b o l i s m of p r o p i o n a t e in Rhodospirillum rUbrum requires~ for its initiation, the presence of carbon dioxide. This observation supports the view t h a t the dissimilation of p r o p i o n a t e begins with a c a r b o x y l a t i o n which yields suecinate. N u m e r o u s investigators h a v e found evidence for this m e c h a n i s m in other organisms, as r e p o r t e d b y STADTMA~ and STADT~L~ (1953) and b y C ~P B E L L (1954). These reviewers also cite evidence for an o x i d a t i o n of p r o p i o n a t e to p y r u v a t e , via acrylate and lactate. The present p a p e r describes investigations of t h e o x i d a t i v e m e t a b o l i s m of p r o p i o n a t e in Rh. rubrum, using substrates labeled with carbon fourteen. The i n h i b i t o r y effect of sodium m a l o n a t e was also investigated. Procedure
Rhodospirillum rubrum (strain S-1, VAN NIEL) Was cultivated anaerobically, under illumination, in a medium containing minerals and yeast extract, as described in an e~rlier paper (CLAYTOn, 1955). Cells from m~ture cultures were washed and resnspended in a mineral medium containing the substrate to be investigated (usually propionate). Following 18 hours' incubation in the light, the cells were washed and resuspended to a density of 6% (v/v) in 0.006 m NaHCO~ solution. At the start of an experiment this suspension was mixed with an equal volume of water containing labeled and unlabeled ("carrier") substrates. The resulting mixture was aerated, in the dark, with air containing 5% CO 2. Samples were withdrawn at intervals for analysis. Analysis of the samples involved partition chromatography, using acidified silica gel eluted with butanol-chloroform mixtures. The procedure was that described by BVLE~ et al. (1952), with a few modifications. Eight grams of silicie acid (Mallinckrodt A. I~.), treated by flotation to remove the finer particles and then dried at 110 ~ C for 24 hours, were mixed in a mortar with 4.5 to 5.0 ml of 0.05 n H~SO 4 until a dry powder was obtainedL 55 m] of chloroform were added, a little
π SIMILAR VOLUMES
## Abstract Experiments with ^14^C labelled propionylβCoA, methylmalonylβCoA and succinylβCoA showed that these compounds are intermediates of propionate synthesis in fermentative metabolism of __Rhodospirillum rubrum.__ The rate of propionate and succinate production is dependent on the CO~2~ conc