Mutations in a Regulator Gene Allowing Pseudomonas aeruginosa 8602 to Grow on Butyramide

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Abstract
SUMMARY Mutants of Pseudomonas aeruginosa 8602 were isolated which, unlike the wild-type strain, utilized butyramide as a growth substrate. One group produced amidases with altered substrate specificities, indicating that the mutations may be in the amidase structural gene. The second group of butyramide-utilizing mutants produced wild-type enzyme and were all con- stitutive. It was concluded that such mutants possessed mutations in an amidase regulator gene which allowed them to synthesize large amounts of amidase in the presence of butyramide. Induction of amid ase synthesis by N-acetylacetamide in the wild-type strain was repressed in a competitive manner by butyramide and other amide analogues, e.g. cyanoacetamide. The constitutive mutant c I I, which could not utilize butyramide for growth, was subject to severe repression of amidase synthesis by butyramide and cyanoacetamide. The regulator mutants which were able to grow on butyramide were all less sensitive to repression by butyramide. Mutant CB 2, a butyramide-utilizing regulator mutant, was relatively insensitive to repression of amidase synthesis by cyanoacetamide whereas strain B 6, a butyramide-utilizing mutant producing an altered enzyme, was as sensitive to repression by cyanoacetamide as its parent strain the constitutive mutant c I I. The contribution of mutations in structural and regulator genes to utilization of novel growth substrates is discussed.

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