Unstable mutations that relieve catabolite repression of tryptophanase synthesis by Escherichia coli.

From strains of Escherichia coli that carry deletions of the trp region, five different mutants were isolated that were capable of synthesizing tryptophanase at unusually high rates in conditions of severe catabolite repression. Notwithstanding the comparative insensitivity to catabolite repression, the rates of tryptophanase synthesis in the mutants were greatly diminished by the introduction of a defective gene for adenyl cyclase. Each of the mutants segregated variants of the parental type. The results of genetic analysis appear to be consistent with the mutants arose by duplication of the tryptophanase gene.