| Abstract: | When bacteriophage T1 was grown on bacteriophage lambda-lysogenic cells, phenotypically mixed particles were formed which had the serum sensitivity, host range, and density of T1 but which gave rise to lambda phage. T1 packaged lambda genomes more efficiently both when the length of the prophage was less than that of wild-type lambda and when the host cell was polylysogenic. Expression of the red genes of lambda or the recE system of Escherichia coli during T1 growth enhanced pickup of lambda by T1, whereas packaging was reduced in recB cells. If donors were singly lysogenic, the expression of transduced lambda genomes as a PFU required lambda-specified excisive recombination, whereas lambda genomes transduced from polylysogens required only lambda- or E. coli-specified general recombination to give a productive infection. |
