Transcription stimulates recombination. I. Specialized transduction of Escherichia coli by lambda trp phages

Specialized transduction of Trp+ by lambda trp phages, whose trp genes were totally under the control of the PL promoter of lambda, was studied. In all cases the efficiency of transduction (EOT) was significantly reduced in homoimmune recipients. In Su- recipients the EOT by phages whose trp gene expression was N-dependent was reduced 2- to 3-fold by the lambda mutant Pam but 30- to 100-fold by an Nam mutant. With phages whose trp gene expression was N-independent, either Pam or Nam caused 2- to 3-fold reduction in the EOT. It was concluded that transcription of the trp genes of the specialized transducing phages had a direct, stimulatory effect on their recombination leading to transduction.