Analysis of evolving lysogenized products of spontaneous zygogenesis in Escherichia coli

Subclonal analysis of spontaneous zygogenesis (Z-mating) products of Escherichia coli K12 was undertaken to grasp the extent of vertical and horizontal evolution in unstable strains expressing one parental or recombinant genome. Isolates were obtained following serial cultures or serial intercrosses. A high diversity of strains was obtained, among which some resumed the phenotype of the partners of the initial or subsequent Z-matings. When non-complementing diploids are infected with a mixture of distinct temperate bacteriophages, lysogenisation occurs at the expenses of the active chromosome only. This event is associated with an alternate expression of prophage and chromosomal genes. Present work provides further evidence for the existence of non-complementing diploidy and opens a novel route for virus research in general.