Acetic acid oxidation by Escherichia coli; quantitative significance of the tricarboxylic acid cycle

Anaerobic growth yields of Aerobacter cloacae and Escherichia coli

Aerobacter cloacae UW-C83 and Escherichia coli K-12 were grown under various anaerobic environments. Y(atp) values were calculated by determination of cell weights and analyses for fermentation products. These Y(atp) values are compared with others reported in the literature. Limitation of growth by factors other than adenosine triphosphate supply is discussed.

METABOLISM OF d -RIBOSE-1-C 14 AND C 14 -LABELED d -GLUCONATE IN AN ENZYME SYSTEM OF THE GENUS PROPIONIBACTERIUM

Stjernholm, Rune L. (Western Reserve University, Cleveland, Ohio) and Frank Flanders . Metabolism of d -ribose-1-C 14 and C 14 -labeled d -gluconate in an enzyme system of the genus Propionibacterium . J. Bacteriol. 84: 563–568. 1962.—Ribose-1-C 14 and potassium gluconate labeled in different positions were incubated with cell-free extracts of Propionibacterium shermanii . The resulting propionate, acetate, and succinate were isolated and the C 14 distribution determined by degradation. It is proposed that the extensive randomization observed is caused by the conversion of the labeled substrates to fructose-6-phosphate via the transketolase-transaldolase sequence followed by the Embden-Meyerhof pathway, and that the triosephosphates produced by these metabolic routes are metabolized via pyruvate to succinate and propionate.

Bacterial permeability: the uptake and oxidation of citrate by Escherichia coli

A direct measurement of total uptake was applied to determine whether surface impermeability could explain why extracts of Escherichia coli can oxidize exogenous citrate but intact cells cannot. The equations for the "space" method are derived and its limitations are pointed out. The observed uptake of citrate was characterized as a variable that was dependent on temperature, pH, external citrate concentration, the species and concentration of cations, and integrity of the cell, but was independent of added energy source, time, and adaptational or mutational processes. Uptake into the citrate space appeared to be a diffusional process. It was concluded that citrate normally diffuses into the cell wall, and under certain environmental conditions may penetrate further into the cell. The lack of correlation between uptake and oxidation of citrate negated the hypothesis of surface impermeability of E. coli to citrate.