Transduction of Gal+ by coliphage T1. II. Role of lambda transcription control in the efficiency of transduction.

One of the crossovers leading to the transduction of Escherichia coli W3350 or one of its derivatives for the Gal(+) marker by T1 grown on donors lysogenic for lambda must occur to the right of the galactose operon. The location of this crossover determined both the rate of transduction and the lambda genes which control the transduction by (lambda-gal)T1. When the crossover occurred either to the left of gene N or the right of the cI gene, it was affected in a positive fashion by the gene product of the N(+) gene. When the crossover occurred either to the left of gene N or between N and gene Q, its efficiency was not significantly affected by the expression of Q(+). However, crossovers to the right of gene Q were greatly stimulated by the presence of a functioning Q gene on the chromosome of (lambda-gal)T1 hybrid. The repressor made by the cI(+) gene of lambda blocked efficient transduction. Therefore, the control of efficient transduction by (lambda-gal)T1 is the same as the control of transcription of lambda. It is concluded that the increased efficiency of transduction by (lambda-gal)T1 in nonimmune recipients is not caused by any particular product of a gene but rather by the process of transcription itself.