On the Relation between Assimilation and Respiration in Suspensions and in Cultures of Escherichia coli

Abstract

The oxidation of acetate, propionate, lactate, pyruvate, glycerol, fumarate, succinate and glucose by washed suspensions of E. coli, as detd. by the Warburg technic, is not carried to completion in phosphate or bicarbonate buffers. The amts. of O2 consumed and of CO2 produced vary with the nature of the substrate but in all cases the results suggest that a portion of the substrate is assimilated by the cells. The respiratory and assimilatory processes appear to be closely connected although it is possible to block assimilation and bring about a complete oxidation of the substrate by adding a suitable conc. of Na azide or of [alpha] dinitrophenol to the bact. suspension. Indirect evidence of assimilation is presented in studies on the growth of E. coli in a synthetic medium, the same relation between extent of oxidation and assimilation being observed in actively proliferating cultures as in washed suspensions of this organism.