Regulation of enzymes of the 3,5-xylenol-degradative pathway in Pseudomonas putida: evidence for a plasmid

Constitutive synthesis of enzymes responsible for methyl group oxidation in 3,5-xylenol degradation and an associated p-cresol methylhydroxylase in Pseudomonas putida NCIB 9869 was shown by their retention at high specific activities in cells transferred from 3,5-xylenol medium to glutamate medium. The specific activities of other enzymes of the 3,5-xylenol pathway declined upon removal of aromatic substrate, consistent with their inducible control. Specific activities of the methyl-oxidizing enzymes showed an eventual decline concomitant with a decrease in the fraction of bacteria capable of growth with 3,5-xylenol; a simultaneous loss of the ability to grow with m-hydroxybenzoate was also observed. The property of 3,5-xylenol utilization could be transferred to another strain of P. putida. It is proposed that enzymes of the 3,5-xylenol pathway and those for conversion of p-cresol to p-hydroxybenzoate are plasmid encoded, that the early methyl-oxidizing enzymes are expressed constitutively, and that the later enzymes are inducible.