Pyrimidine ribonucleoside catabolism in Pseudomonas fluorescens biotype A

Abstract

The pyrimidine ribonucleosides uridine or cytidine were shown to serve as a source of nitrogen or carbon for the growth of Pseudomonas fluorescens strain A126. After incubation of either pyrimidine ribonucleoside with extracts of this strain, the resultant catabolic products were detected by thin-layer chromatography. It was found that pyrimidine ribonucleoside catabolism in this pseudomonad involved the enzymes nucleoside hydrolase and cytosine deaminase. The specific activities of both these enzymes could be influenced by the nitrogen or carbon source present in the medium.

Pyrimidine base and ribonucleoside catabolic enzyme activities of the Pseudomonas diminuta group

“…As a carbon source, dihydrothymine or ribose did not support the growth of either type strain after 8 days at 30°C. The inability of both type strains to utilize pyrimidine bases and ribonucleosides, which may be related to membrane permeability, contrasted what has been observed for the more nutritionally versatile members of the P. fluorescens and P. alcaligenes DNA homology groups [4,5,10].…”

“…In this report, the presence of enzymes associated with pyrimidine base and ribonucleoside catabolism was investigated in the type strains of the P. diminuta DNA homology group. Initially, it was not clear whether pyrimidine ribonucleoside catabolism in these strains involved the enzyme nucleoside hydrolase [4,5,14,15] or whether catabolism occurred by means of the enzymes cytidine deaminase and uridine phosphorylase as has been found in enteric bacteria [16]. This prompted an examination into the nature of pyrimidine catabolic enzymes present in the type strains of the P. diminuta group.…”

“…Catabolite repression of nucleoside hydrolase synthesis in P. vesicularis by glucose may be a possible explanation. Nucleoside hydrolase has been shown to be active in P. fluorescens and in the type strains of the P. alcaligenes DNA homology group [4,5]. Carbon source has also been shown to affect nucleoside hydrolase levels in P. fluorescens [4].…”

“…Once the solvent front reached 1 cm from the top of the plate, the plate was removed from the tank and allowed to dry. Cytidine, uridine, cytosine, uracil were located on the thin-layer plates by virtue of their UV fluorescence while ribose and ribose-l-phosphate were detected by their brown color after spraying the plates with an aniline phosphate reagent [4].…”

“…Despite previous studies examining pyrimidine metabolism in species of the Pseudomonas fluorescens DNA homology group as well as the Pseudomonas alcaligenes DNA homology group [4,5], which are both classified within rRNA homology group I [1], an investigation of pyrimidine metabolism in the P. diminuta group has not been undertaken. In this study, the presence of pyrimidine base and ribonucleoside catabolic enzyme activities in the type strains of P. diminuta and P. L'esicularis was explored.…”