THE PRESENCE OF THE TRICARBOXYLIC ACID CYCLE IN THE CILIATE COLPIDIUM CAMPYLUM

Abstract

The addition of pyruvate to colpidia respiring in buffer, results in an increase of the QO2 from the endogenous value of 13.2 to 26.3. 0.081 mg. of pyruvate are utilized/ mg. dry weight of cells/hr. The pyruvate effect is inhibited by malonate. Fumarate, succinate, and [alpha] -ketoglutarate release the malonate inhibition. Succinate, [plus or minus]-ketoglutarate, malate, fumarate, and oxaloacetate increase the QO2 to values of 27.1, 26.8, 25.1, 26.1, and 24.5, respectively. In the presence of malonate, added fumarate increases the recovery of succinate from pyruvate 5-fold. Fumarate and [alpha]-ketoglutarate are recovered when pyruvate is utilized as the sole substrate. The recovery of a-ketoglutarate is increased 142% by the addition of fumarate. Fumarate and pyruvate are recovered when oxaloacetate is utilized as the sole substrate. Citrate does not increase the oxygen uptake of Colpidium nor does this compound release malonate inhibition. Hence, citrate apparently does not occupy a major position in the metabolism of Colpidium.