Comparative physiological studies on four species of hemofiagellates in culture. III. Effect of the Krebs' cycles intermediates on the respiration

Abstract

The effect of the Krebs' cycle intermediates upon respiration of the culture forms of Endotrypanum schaudinni, Leishmania enriettii, Schizotrypanum vespertilionis and S. cruzi was examined at two different hydrogen ion concen­trations. At pH 7.2, low stimulations with some of the intermediates were ob­served. At pH 5.0 the stimulations in general were more evident, and alpha­ ketoglutarate, malate, and pyruvate were oxidized by E. schaudinni at the same rate as glucose while succinate produced a respiratory stimulation 35 per cent higher than that of glucose. A t the same low pH, the other three species were able to utilize some pyruvate, whereas acetate inhibited all of them. The increase in respiration produced by the tricarboxylic acids was almost negligible, regardless of the pH, and in some instances the substances rather had a depressive action on the respiration. It is believed that the tricarboxylic acid cycle is present in the four species and the possibility of its importance in roles other than energy production, in Leishmania and Schizotrypanum, is discussed.