The Role of Oxygen in the Regulation of Glucose Metabolism, Transport and the Tricarboxylic Acid Cycle in Pseudomonas aeruginosa

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Abstract
The effect of dissolved O2 concentration on the metabolism of glucose in P. aeruginosa was studied with chemostat cultures using single-step and gradual transitions from ammonium or glucose limitation to O2 limitation and studying transient and steady states. The pathway of glucose metabolism was regulated by the availability of O2. The organism responded to O2 limitation by adjusting its metabolism of glucose from the extracellular direct oxidative pathway, which produces gluconate and 2-oxogluconate, to the intracellular phosphorylative route. This change was a consequence of decreased activities of glucose dehydrogenase and gluconate dehydrogenase and of the transport systems for gluconate and 2-oxogluconate, and an increased activity of glucose transport, while relatively high activities of hexokinase and glucose-6-phosphate dehydrogenase were maintained. Citrate synthase, isocitrate dehydrogenase and malate dehydrogenase activities responded to changes in dissolved O2 concentration rather than to changes in the glucose or ammonium concentrations. The effect of O2 limitation on the oxo-acid dehydrogenases and aconitase was probably due, wholly or in part, to repression by glucose consequent upon the increase in residual glucose concentration. Succinate dehydrogenase was repressed by an increase in ammonium concentration under an O2 limitation.