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Introduction to Lambda

A. D. Hershey, William Dove


The bacteriophages form a diverse collection of viruses that multiply in bacterial cells. This book describes the variety called λ and some of its relatives, which multiply in Escherichia coli. Chapter 1 presents general characteristics of the λ group, and explains how λ came to be the subject of intensive study.

The classical phages destroy their host cells by lysis. Lambda causes lysis too, but can also propagate in a form that permits joint multiplication of phage and host. Phages possessing this added potentiality are called temperate, in distinction from the broad class of intemperate or virulent species, which cannot reproduce without destroying their host cells.

Lambda is also one of a few well known genetic elements, called episomes, that are able to multiply in the cell either autonomously or as part of the bacterial chromosome. In fact λ and the fertility agent F of E. coli are historical prototypes of the class. Campbell (1969) presents the comparative biology of episomes.

For newcomers to phage research, Stent’s Molecular Biology of Bacterial Viruses (1963) can be recommended as a source book.

Lambda phage particles are about half protein and half DNA. Each contains one double-stranded DNA molecule encapsulated in an icosahedral head, 0.05 μ in diameter, from which projects a tubular tail, 0.15 μ long (Chapter 14). The DNA molecule is made from the usual four bases and weighs about 31 million daltons. Phage particles can be prepared in milligram quantities for analysis of various sorts.

Lambda is...

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