. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. METABOLISM IN COLPIDIUM 259 30 25 20 0) o _o o_ 3 1. 10 20 30 time in minutes 40 50 60 FIGURE 2. Effect of malonate and fumarate on oxygen uptake in Colpidium. Modified Hahnert's solution, pH Gas phase, O2. Temperature, ° C. Curve 1, no added sub- strate ; curve 2, M pyruvate; curve 3, M pyruvate + M malonate; curve 4, M pyruvate + M malonate + M fumarate. increase in the rate of oxygen uptake (Fig. 1). There is a utilization of mg. of pyruvate per mg. dry weight of cells per hou
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. METABOLISM IN COLPIDIUM 259 30 25 20 0) o _o o_ 3 1. 10 20 30 time in minutes 40 50 60 FIGURE 2. Effect of malonate and fumarate on oxygen uptake in Colpidium. Modified Hahnert's solution, pH Gas phase, O2. Temperature, ° C. Curve 1, no added sub- strate ; curve 2, M pyruvate; curve 3, M pyruvate + M malonate; curve 4, M pyruvate + M malonate + M fumarate. increase in the rate of oxygen uptake (Fig. 1). There is a utilization of mg. of pyruvate per mg. dry weight of cells per hour (Table II). If the tricarboxylic acid cycle plays a role in the metabolism of Colpidium, the oxygen uptake in the presence of pyruvate should be inhibited by malonate. This inhibition should be released upon the addition of fumarate. Figure 2 shows that M pyruvate increases the Q02 from the endogenous value of to , an increase of 99 per cent. In the presence of pyruvate and M malonate the Qo2 is , 83 per cent inhibition of the pyruvate effect. The Qo2 is restored to a value of by the addition of M fumarate, an 89 per cent recovery of the malonate inhibition. The effect of other acids of the tricarboxylic acid cycle on oxygen uptake is shown in Table I. Succinate results in an increased Q02 of 105 per cent; a- ketoglutarate 102 per cent; fumarate 90 per cent; malate 97 per cent; and oxalo- acetate, an increase of 85 per cent. The quantities of metabolites recovered from various substrates are shown in Table II and III. Fumarate and a-ketoglutarate are recovered in approximately equal amounts when pyruvate is the substrate. The addition of fumarate to pyruvate increases the recovery of a-ketoglutarate by 142 per cent. Fumarate and pyruvate are recovered in a ratio of approximately 1 to 4 when oxaloacetate is utilized as a substrate. Table III shows that as a result of the fumarate release of malonate inhibition, there is an added utilization o
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