THE ESTABLISHMENT OF LYSOGENICITY IN ESCHERICHIA COLI

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Abstract
Cells of a strain of E. coli K12 sensitive to the "temperate" phage lambda may give any of 5 different responses after exposure to the phage: lytic, lysogenic, refractory (unaffected by the phage), lethal, and hereditarily resistant. With the exception of the rare resistant type, these responses are governed by non-genetic factors; the proportions of the response types are detd. by the physiol. conditions of the culture and by the phage multiplicity. A cell infected with a single lambda particle could give rise to a lysogenic clone. Individual clones derived from lambda-infected cells were analyzed for the presence of lysogenic cells, non-lysogenic cells, and free phage. Cells which gave rise to clones of cells did not, in addition, produce free phage. Thus, the decision as to whether lysis or cell multiplication is to take place is made by the bacterium either before or shortly after infection. However, during the 1st hr. after infection the establishment of lambda prophage leading to lysogenesis can be suppressed in some or all cells in a clone by growing the cells at temps, above 20[degree]C. The observations are compatible with the hypothesis that the infecting phage which leads to lysogenesis acts as a cytoplasmic particle immediately after infection of the cell and later becomes attached to a regularly-inherited cell constituent.