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Updated: Jun 19, 2026

Following Cell-fate in E. coli After Infection by Phage Lambda
Published on: October 14, 2011
Defiance of stable lysogeny reveals hidden infection dynamics of phage Lambda
Kevin Broux1, Leonard E Bäcker1, Dries Oome1,2
1Department of Microbial and Molecular Systems, KU Leuven, Leuven 3001, Belgium.
Abstract:
Stable prophage establishment is considered a quintessential response of temperate phages when faced with host cell depletion. Scrutinizing this behavior in model phage λ, however, revealed that many λ-chromosomes avoid stable integration in the host chromosome, and rather assume a nonintegrated prophage-like (or pλ) state inside the cell that keeps expressing CI-based immunity and becomes asymmetrically segregated. This creates a heterogeneous population of host cells that are either i) immune by stably carrying an integrated λ prophage, ii) immune by carrying a pλ-episome, or iii) λ-free and transiently immune by segregating from a pλ-carrier. Superinfection of these immune cells drains the number of λ-virions and creates more pλ-episomes that prolong the immunity and expansion of the λ-free subpopulation. The subsequent decline in λ-virions causes cytoplasmically inherited CI-levels in λ-free siblings to dilute out, poising them for renewed lytic consumption by λ. These overlooked pλ-dynamics attenuate the importance of prophage establishment and permit a more productive phage-host coexistence.
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