Recombination and phenotypic mixing during phage growth in strains of Escherichia coli doubly lysogenic for coliphage lambda

Abstract

Strains of Escherichia coli C112 doubly lysogenic for genetically marked strains of coliphage lambda were prepared by superinfection of singly lysogenic bacteria. A particular recombinant constituted about one-half of the total phage in mass lysates resulting from spontaneous and UV-induced lysis of all strains. This recombinant carried the clear plaque marker of the first prophage to be established within the cell and the host range marker of the second prophage. Both the clear marker and the host range marker of this recombinant were independently in excess of their respective alleles. It is concluded that in lambda double lysogens both prophages establish and maintain a definite orientation with respect to one another and to the neighboring bacterial nuclear structures and that this is reflected in the type of phage released following lysis. In all lysates there was a poor correlation between the proportions of host range genotypes and phenotypes. Although the relative proportions of the host range markers fluctuated with the order of lysogenization by the prophages bearing them, the proportion of h + phenotypes was invariably higher than that of h phenotypes. Order of lysogenization exerted no influence on pheotype proportion. Association of individual host range genotypes with noncorresponding phenotypes, that is, phenotypic mixing, was observed in all lysates.