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A study of the intermediate metabolism of Pseudomonas aeruginosa Ney, Phyllis Winifred

Abstract

The intermediate metabolism of P. aeruginoss (A.T.C. 9027) has been studied manometrically to determine the pathway of glucose breakdown. Since the organism was found to respond to increased amounts of iron and since no positive evidence of an anaerobic respiratory mechanism could be contained it was concluded that this organism was an obligate aerobe. Among those compounds rapidly attacked by resting suspensions of cells harvested from a glucose-ammonium succinate medium were succinic acid, glucose, gluconic acid and 2-ketogluconic acid. However, 5-ketogluconic acid was not attacked. Concentrations of malonate as high as 5 x 10⁻² M had no effect on the oxidation of glucose or succinate by these cells, however they did markedly retard the rate of adaptation to succinate by cells harvested from a glucose ammonium phosphate medium. By growing the cells on a completely inorganic medium plus specific substrate, it was possible to show that glucose grown cells rapidly oxidized gluconic and 2-ketogluconic acids but short periods of adaptation were required for the utilization of succinic acid (20-30 mins.) Moreover it appeared that cells harvested from succinate and lactate-ammonium phosphate media were not pre-adapted to the breakdown of glucose. The rate of oxidation was initially slow, progressively increasing throughout the experimental period. To confirm the presence of adaptive enzymes for the dissimilation of glucose, a comparison was made of the ability of cells grown in the presence of either glucose or acetate to attack glucose. Whereas cells harvested from a glucose medium oxidized this substrate at a rapid and constant rate, cells grown in the presence of acetate showed no activity until after one hour of incubation. Since glucose was attacked by an adaptive enzyme system it was possible to study intermediate glucose metabolism by means of the simultaneous adaptation technique of Stanier. A comparison of the oxidative activity of glucose and acetate cells showed that while glucose cells attacked glucose, gluconic acid and 2-ketogluconic acid rapidly and directly, acetate cells required a period of adaptation of at least one hour before they could oxidize these substrates. It was therefore concluded that the breakdown of glucose by this aerobic organism proceeded by way of gluconic acid and 2-ketogluconic acid, and that succinic acid was not an intermediate metabolite.

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