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Oxidative assimilation of glucose by aerobic bacteria Tomlinson, Geraldine Ann

Abstract

Oxidative assimilation of glucose-U-C¹⁴ by several aerobic bacteria was found to involve the assimilation of radioactivity into nitrogenous cell components, principally proteinaceous, in conjunction with the reincorporation of endogenously produced ammonia. In one of these bacteria, Pseudomonas aeruginosa, if the cells were starved or treated with chloramphenicol/ prior to glucose-C¹⁴ the amount of assimilation, especially into protein, was decreased. The incorporation into nucleic acids and lipids was increased by the antibiotic, but was only slightly affected by starvation. A determination of the cytological sites of the assimilated material showed that, in control cell extracts, the soluble proteins of the cytoplasm contained most of the C¹⁴. Starved or antibiotic treated cell fractions had substantially less of the label in these proteins, whereas the radioactivity incorporated into the ribosomal ribonucleic acid and the "membrane" lipids was greater. A study of the aminoacyl-soluble ribonucleic acid synthetases in P. aeruginosa revealed that these enzymes were present only in the cytoplasm. Starving the cells resulted in decreased activity of the synthetases, but they were rapidly reactivated during oxidative assimilation. The large amount of heterologous reactions between bacterial soluble ribonucleic acids and synthetases indicated that little species specificity existed. However, cross reactions between the systems in bakers' yeast and the bacteria were poor, showing that some degree of species specificity was present in these instances. Preliminary experiments on the route of assimilation of ammonia in P. aeruginosa and in P. fluorescens gave no evidence for the direct amination of pyruvate by alanine dehydrogenase, but did demonstrate a requirement for concurrent substrate oxidation while ammonia was being incorporated. In contrast, several lines of evidence indicated that ammonia was assimilated via ∝-ketoglutarate in P. aeruginosa.

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