Mutants of strain 8602 were isolated which were unable to produce an aliphatic amidase (acylamide amidohydrolase, EC and could not grow on acetamide as a carbon or nitrogen source. Amidase-constitutive mutants, producing amidase in the absence of inducing amides, were isolated by selection on succinate+formamide agar. Sixteen mutants were magno-constitutive non-inducible mutants producing amidase at about the same rate or greater than the fully induced wild-type strain. Amidase synthesis in one magno-constitutive mutant was repressed by the non-substrate inducer -acetylacetamide, but the others were not affected in any way. Six mutants were semi-constitutive, producing amidase at 10–50% of the rate of the magno-constitutive mutants and were induced by -acetylacetamide. Most of the constitutive mutants were very sensitive to catabolite repression by succinate in pyruvate medium, but succinate produced only partial repression of one magno-constitutive mutant and three semi-constitutive mutants; one semi-constitutive mutant was not repressed except in the presence of inducer.

Six mutants isolated from succinate + formamide agar had altered inducer specificity and were induced to form amidase by formamide, which is a very poor inducer for the wild-type strain. The formamide-inducible mutants were also sensitive to catabolite repression by succinate although one mutant was only partially repressed.

Phage F 116 was used to transduce the amidase structural and regulator genes. In crosses between constitutive mutants of Pseudomonas aeruginosa as donors and amidase-negative mutants as recipients, the two characters were co-transduced with frequencies of 80–100%. Similarly, in crosses between formamide-inducible and amidase-negative mutants these two characters were co-transduced with frequencies of 89–96%. The amidase structural and regulator genes are considered to be closely linked.


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