Carbon Dioxide Fixation by Microorganisms

Abstract

The place occupied by the photosynthetic mechanism of energy conversion in the stream of biochemical evolution has been the subject of considerable speculation (van Niel, 1949;Blum, 1937). It is clear, however, that in order to establish such a place, a more or less definite notion of the nature of the entire evolutionary stream is necessary. In recent years the idea that the stream is flowing in the direction of the loss of synthetic biochemical abilities has gained a special prominence, particularly as a result of laboratory experimentation as well as the observation of naturally occurring systems (Beadle, 1945;Tatum, 1946;Knight, 1950). Such a view quite clearly places the photosynthetic mechanism very near the beginning. However, a variety of very powerful arguments have been adduced (Oparin, 1938;Haldane, 1934) against the sudden appearance of the very complex, completely autotrophic organism containing extremely involved biosynthetic sequences in an essentially inorganic world.A mechanism has been proposed (Horowitz, 1945) for the evolution of these very involved biosynthetic sequences leading to complex compounds by the gradual acquisition of synthetic abilities. Such a view of the evolutionary stream would, of course, place the photosynthetic energy converting system near the top or the end rather than at the bottom of the scale or near the beginning of the stream. It seemed to us not unreasonable to suppose that the entire evolutionary stream consists of both types of change, the one involving increasing biosynthetic abilities being the earlier leg, leading ultimately to completely autotrophic organisms, and the other involving the loss of biosynthetic abilities being a second leg and becoming the major direction comparatively later on the evolutionary time scale.The fossil record that is left to us is, of course, of very recent origin on such a scale. Presumably we have no direct geological record of the events on the rising leg of such a stream. It is, however, conceivable that some heterotrophic organisms alive today might represent stages on the rising leg, and the problem becomes the one of seeking to find criteria to determine whether or not such an organism represents a precursor to an autotroph or a product of the loss of synthetic abilities from an autotroph.

The utilization of glycogen and accumulation of some intermediates during anaerobiosis in Mytilus edulis L.

“…"['he results with the sea mussel indicate that the Embden-Meyerhof scheme does not operate the same as in vertebrates. This is in agreement with the observation of many authors that succinate rather than lactate is the major fermentation product of a number of micro-organisms, intestinal helminths and bivalves which depend on anaerobic metabolism for their supply of energy (Lynch & Calvin, 1952;Saz & Beuding, 1966;Simpson & Awapara, 1966;Hammen, 1969). Stokes & Awapara (1968) incubated under nitrogen the mantle of Rangia euneata, a brackish water bivalve, with randomly labeled 14C-glucose.…”

Kinetic Studies of the Oxidative Assimilation of Acetate by a Non-photosynthetic Strain of Euglena gracilis

“…6 be correct, Soluble I should consist largely of intermediates in the conversion of acetate to carbohydrates, presumably Krebs cycle acids, the phosphorylated intermediates of glucose metabolism and oligosaccharides. In partial support of this theory, Lynch & Calvin (1952, 1953 found that, of the acetate methyl-carbon incorporated into ethanol-soluble materials during incubation for 12 min. in the dark, nearly 50 yo was in the form of phosphorylated intermediates, 4 yo in the form of ' dextrins ', and about 25 yo in the form of amino acids related to the Krebs cycle.…”

Respiration of the Mycelia and Mitochondria of the Filamentous Watermold, Allomyces Macrogynus

“…Lynch and Calvin (25) found that a considerable amount of radioactivity was incorporated into a water-soluble polysaceharide when Allomyces arbuscula was suspended in a labeled bicarbonate solution-indicating that this polysaccharide was metabolically active. It may serve as an endogenous substrate.…”