Catabolite Repression and the Induction of Amidase Synthesis by Pseudomonas aeruginosa 8602 in Continuous Culture

Abstract

Pseudomonas aeruginosa 8602 was grown in continuous culture under steady-state conditions in a C-limited medium containing either 20 mM-acetamide or 20 mM-acetamide +10 mM-succinate. The amidase specific activity measured at various dilution rates had a sharp peak at a dilution rate of 0-30-0-35 hr.-1. Fully constitutive mutants (C II and L 9) gave curves for amidase activity with the highest values at very low dilution rates (0-05-0-10 hr.-1) and these decreased as the dilution rate increased. A semi-constitutive mutant (C 17) gave a curve intermediate between that of the wild-type strain and the fully constitutive mutant (C 11). Mutants with decreased sensitivity to catabolite repression by succinate gave curves which declined less steeply at the higher dilution rates. Mutant L 9, a fully constitutive mutant with decreased sensitivity to catabolite repression, had higher specific activities than mutant C II at the equivalent dilution rates. Mutant L n, and inducible mutant with decreased catabolite repressibility, had higher amidase specific activities at high, dilution rates than the wild-type inducible strain. In continuous culture under steady-state conditions, the specific activity of the inducible amidase of P. aeruginosa is determined by the balance between induction and catabolite repression; and catabolite repression is directly related to the growth rate of the culture.