Energy relationships in carbohydrate assimilation by Escherichia coli.

From studies employing the techniques of manometry, Clifton (1950) has further developed the concept first enunciated by Kluyver (1930, 1931) that the energy resident in a substrate molecule would not provide a propitious criterion for predicting the extent of its assimilability by the bacterial cell. He noted, for example, the same degree of assimilation with the monobasic organic compounds, lactate and pyruvate, despite the greater free energy of oxidation of the former; likewise with the dibasic compounds succinate and fumarate, oxidation was accompanied by the same amount of assimilation, although the reaction in the first instance is attended by a greater free energy change (Clifton and Logan, 1939). Thermodynamically it could be anticipated that, in a set of reactions involving the liberation of energy, the organism might profit more from those processes yielding greater portions of energy. Clifton, however, as did Kluyver, reasoned that intermediates of these reactions, in serving as building blocks for the numerous syntheses carried on by the cell, would assume a significance as great as, if not greater than the extent of energy evolved in oxidation. Along with Kluyver's concept of the thermodynamically improbable state of the bacteriuim (1931), Clifton (1950) and others (van Niel, 1949) have further formulated the concept of the cell as a transformer and converter of substrate substance rather than just as an engine transforming energy and subserving the themes of thermodynamics. In this paper is described a series of experiments designed to test the validity of the Kluyver concept as extended by Clifton.