Variability in the enzyme properties of Pseudomonas aeruginosa strain 2x oxidizing p-xylene

A culture of Pseudomonas aeruginosa 2x was observed for its spontaneous variability for growth on p-xylene and the intermediate products of its metabolism. The highest variability was found for ability to grow on p-xylene and pyrocatechol, and a variability an order of magnitude lower was found for ability to grow on protocatechuate and p-toluate. No variability was found for the character "ability to grow on p-hydroxybenzoate." The activity of the key enzymes for the oxidation of p-xylene was studied in p-xylene-negative strains. The difference between the p-xylene-positive wild type strain and the spontaneous p-xylene-negative strains was found to be linked to changes in the regulatory mechanisms for several enzymes: p-xylene methylhydroxylase and the enzymes involved in the breakdown of the aromatic ring. In addition, the appearance of p-xylene-negative strains was linked with a significant fall in the specific activity of all enzymes, except pyrocatechuase, which was replaced by metapyrocatechuase on a number of substrates.