STUDIES ON LYSOGENESIS I

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Abstract
A lysogenic strain of E. coli was shown to carry 3 bacteriophages P1, P2, and P3, active on a strain of Shigella dysenteriae. These phages are distinguishable for serological and plaque morphology characters. Actively growing lysogenic cultures liberate phage spontaneously at a constant rate; this is due to maturation of the phage and lysis in a constant small proportion of cells. All single cell isolates from the lysogenic strain produce all 3 phages; each cell, therefore, must carry the determinants ("prophages") of all 3 phages. When a cell lyses and liberates a cluster of phage particles, though, these are all of one type, either P1, or P2, or P3. No mixed bursts of phage have been observed. A discussion of the possible relationships between prophage and mature phage is given in the attempt to interpret these data. A technic for assaying free phage admixed with large amts. of lysogenic bacteria is described, which involves selective killing of the lysogenic cells with streptomycin, the phages being resistant to this drug.