Pyrimidine Biosynthesis and Ribonucleoside Metabolism in Species of <i>Pseudomonas</i>

Pyrimidine biosynthesis and ribonucleoside metabolism in species of <i>Pseudomonas</i> was the focus of this review, in relation to their current taxonomic assignments in different homology groups. It was of interest to learn whether pyrimidine biosynthesis in taxonomically related species of <i>Pseudomonas</i> was regulated in a similar fashion by pyrimidine base supplementation or by pyrimidine limitation of pyrimidine auxotrophic strains. It was concluded that the regulation of pyrimidine biosynthesis in <i>Pseudomonas</i> species could not be correlated with their taxonomic assignment into a specific homology group. Pyrimidine ribonucleoside metabolism in <i>Pseudomonas</i> species primarily involved the pyrimidine ribonucleoside salvage enzymes nucleoside hydrolase and cytosine deaminase, independently of the <i>Pseudomonas</i> homology group to which the species was assigned. Similarly, pyrimidine base catabolism was shown to be active in different taxonomic homology groups of <i>Pseudomonas</i>. Although the number of studies exploring the catabolism of the pyrimidine bases uracil and thymine was limited in scope, it did appear that the presence of the pyrimidine base reductive pathway of pyrimidine catabolism was a commonality observed for the species of <i>Pseudomonas</i> investigated. There also appeared to be a connection between pyrimidine ribonucleoside degradation and the catabolism of pyrimidine bases in providing a cellular source of carbon or nitrogen independently of which homology group the species of <i>Pseudomonas</i> were assigned to.