Regulation of phenol degradation in Pseudomonas putida

In order to characterize the ability of Pseudomonas putida (TREVISAN 1889) MIGULA 1895 strain H to degrade various mono- and diphenolic aromatic compounds, respiratory activities towards phenol, catechol, and the cresol isomers were determined. The following rates of oxygen uptake (QO2) were obtained with resting phenol-grown cells: phenol -- 229, o-cresol -- 231, m-cresol -- 43, p-cresol -- 200, catechol -- 262. All these compounds were oxidized by a two-phase-kinetics, the first phase is characterized by a higher oxidation rate than the second. The oxidation of phenol as well as of p-cresol was found to be substrate-inhibited at concentrations above 0.25 mM. A Ki-value of 100 mg/l was calculated for phenol oxidation. The phenol-degrading enzyme system is induced, probably coordinately, by phenol and the cresol isomers. In strain H the degradation of phenol is carried out simultaneously with the assimilation of natural carbohydrates like glucose and sodium pyruvate. Aniline as well as sodium benzoate, though not metabolized by strain H, cause a concentration-dependent inhibition of phenol degradation in resting phenol-grown cells of that strain. The mechanism of this inhibition is discussed.