Research on phage λ: a lucky choice

Bacteriophage λ is a paradigm in the field of gene regulation and one of the best-understood systems in genetic regulatory biology. A so-called Genetic Switch determines the mechanisms by which λ transitions to its dual lifestyles-lytic or lysogenic. When λ initiates the lysogenic lifestyle, the phage-encoded CI repressor binds cooperatively to multi-partite operators in a defined pattern that autoregulates repression of phage lytic promoters as well as activation of the lysogenic promoter. The study of this genetic switch and related earlier research on phage λ revealed the main principles of gene expression and regulation in molecular biology. This article describes the underlying molecular details of λ lysogeny, as it is currently understood.