UBC Theses and Dissertations
Catabolism and transport of arginine by Pseudomonas aeruginosa Cook, Kathleen Anne
Pseudomonas aeruginosa was shown to constitutively degrade arginine via the arginine dihydrolase pathway to ornithine, which was converted both to glutamate and to putrescine. The conversion of ornithine to glutamate appeared to be the major route of arginine degradation in this organism, and was induced to higher activity after growth of the cells with arginine as the sole source of carbon and nitrogen. P. aeruginosa did not further degrade putrescine constitutively. However, growth of the cells in arginine resulted in a partial induction of succinic semialdehyde dehydrogenase, an enzyme functioning in putrescine degradation. The anabolic ornithine transcarbamylase of P. aeruginosa was repressed after growth of the organism in the presence of arginine. Pseudomonas putida and Pseudomonas fluorescens also possessed the ability to constitutively convert arginine to putrescine via the intermediates, citrulline and ornithine. However, these organisms did not oxidize arginine to the same extent as did P. aeruginosa. P. aeruginosa grew in a mixture of glucose and arginine in the presence of ammonium ions without exhibiting a diauxie effect. Glucose and arginine were oxidized concomitantly when supplied as a mixed substrate, by both growing cells and resting cell suspensions. However, assimilation studies showed that the two substrates were used to serve somewhat different biosynthetic needs. Growth of P. aeruginosa in arginine caused an increase in the rates of transport of arginine, lysine, ornithine and citrulline. Kinetic studies of arginine uptake demonstrated the presence of two uptake systems with different affinities for arginine. Inhibition studies indicated that arginine was transported by two uptake systems: a permease specific for arginine, and, with a lower affinity, for ornithine; and a general permease, which transported all the basic amino acids. Polyamines appeared to be transported by an uptake system which was induced to higher levels after growth of the cells with either arginine or putrescine as the sole source of carbon and nitrogen. P. aeruginosa was found to maintain a stable pool of putrescine when supplied with exogenous ¹⁴C-arginine or ¹⁴C-putrescine, even when the organism had previously been induced to degrade these substrates. A physical fractionation of the cells indicated that the major portion of this pool was located in the soluble cytoplasm.
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