The Process of Infection with Bacteriophage ΦX174: VIII. Centrifugal Analysis in Alkaline Media of the RF DNA at Various Stages of Infection

Abstract

Upon sedimentation, in alkali at low ionic strength of the nucleic acid extracted from ΦX174-infected cells, parental label appears in the 33 s (denatured double-stranded DNA ring), 23 s (native or renatured double-stranded DNA ring) and 14 s (single-stranded DNA ring) infective components. By use of density-labeled parental virus, it is demonstrated that the 23 s component is a double-stranded DNA and that there is a several-fold synthesis of this component during infection. From an analysis of the results at a very early stage of infection, the 23 s component appears to have 1/20 the specific infectivity of the viral DNA. Upon density-gradient equilibrium centrifugation in alkali of the nucleic acid extracted from ΦX-infected cells, parental label can be found, under varying conditions, in all four infective density components. Components ρ-1 and ρ-3 appear to be double-stranded, ρ-2 and ρ-4 to be single-stranded. Formation of the lighter ρ-3 and ρ-4 components is inhibited by chloramphenicol.

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