[Nucleoside catabolism study of Pseudomonas putida and Pseudomonas trifolii]

No activity of specific nucleoside phosphorylases was detected in Pseudomonas putida; as the result, its cells cannot grow on various nucleosides using them as carbon sources. Insignificant growth on ribonucleosides, viz. inosine and uridine, should be attributed to the activity of hydrolases in the cell. In contrast, Pseudomonas trifolii is capable of normal growth on various nucleosides using them as a sole source of carbon. Accordingly, the cell extracts display the activities of enzymes involved in the catabolism of nucleosides, namely, the so-called deo enzymes. Methods developed for E. coli were used to obtain mutants in the genes dra, tpp and drm as well as in regulatory loci negatively controlling the activity of deo genes in Ps. trifolii. Like in E. coli, cytidine and thymidine induce the activity of deo genes in Ps. trifolii.