On the induction of a recombination-deficient mutant of Escherichia coli K-12

Abstract

A lysogenic, recombination-deficient bacterial mutant (rec⁻) can be induced to produce λ ind⁻ C587 by a temperature shift, although it does not produce phage after u.v. irradiation when lysogenic for wild λ. When this mutant (rec⁻) was made colicinogenic for colicins E2 and I, colicin production was found not to be inducible.Superinfection of irradiated lysogenic rec⁻ (λ) bacteria, at doses of irradiation that did not reduce their capacity to produce phage λ, was not productive. It seems therefore that a certain product(s) that usually arises following u.v. irradiation in rec⁺ cells, and triggers the induction of lysogenic and colicinogenic cells by causing loss of immunity or repression, is not produced in the rec⁻ mutant. However, immunity is lost and the prophage is induced after a temperature shift in rec⁻ cells which are lysogenic for λ ind⁻ C857.