Polyamine biosynthesis in Escherichia coli: construction of polyamine-deficient mutants

Previous work is summarized on the biosynthetic pathway for polyamines in Escherichia coli. Deletion mutants have been obtained in the various biosynthetic steps, resulting in cells with no polyamines. These mutants grow at one-third the rate of polyamine-supplemented cultures and can serve as suitable hosts for bacteriophages T4, T7, Q beta, and f2. The major effects of polyamine deficiency in these polyamine-deficient strains are: (i) these cells do not serve as hosts for bacteriophage gamma and (ii) polyamine-deficient male strains have defects which are attributable to a decrease in the stability of the male pili, namely, decreased numbers of recombinants in Hfr crosses and poorer adsorption of the male-specific bacteriophages f1, f2, and Q beta. One polyamine-deficient strain has been developed which becomes absolutely dependent on polyamines for growth if it also contains a specific rpsL (strA) mutation.