Mutants of Pseudomonas aeruginosa strain 8602 were isolated which were unable to produce an aliphatic amidase (acylamide amidohydrolase, EC 3.5.1.4) 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 N-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 N-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.
CohenG. N.,
JacobF.1959; Sur la répréssion de la synthase des enzymes intervenantdans la formation du tryptophane chez Escherichia coli. C.r.hebd. Seanc.Acad. Sci. Paris 248:3490
CohnM.,
HoribataK.1959; Physiology of the inhibition by glucose of the induced synthesis of the β-galactosidase-enzyme system of Escherichia coli. J. Bact. 78:624
CollinsJ. F.,
MandelstamJ.,
PollockM. R.,
RichmondM. H.,
SneathP. H. A.1965; A suggested phenotypic classification and terminology for enzyme mutants in micro-organisms. Nature, Lond. 208:841
DubnauD. A.,
PollockM. R.1965; The genetics of Bacillus licheniformis penicillinase: a preliminary analysis from studies on mutation and interstrain and intra-strain transformations. J. gen. Microbiol. 41:7
JacobF.,
AdelbergE. A.1959; Transfer de caracteres gen6tique par incorporation au facteursexueld Escherichia coli. C.r.hebd. Seanc. Acad. Sci., Paris 249:189
LoomisW. F.,
MagasanikB.1964; The relation of catabolite repression to the induction system for β-galactosidase in Escherichia coli. J. mol. Biol. 8:417
MandelstamJ.,
JacobyG. A.1965; Induction and multi-sensitive end-product repression in the enzymic pathway degrading mandelate in Pseudomonas fluorescens. Biochem. J. 94:569