History, Fame, & Fortune
Bacteriophage lambda, originally obtained from a clinical isolate of E. coli lysogenic for this phage (1), was an important tool in the invention of molecular biology. Lambda is the major prototype for temperate phage biology, for specialized transduction, and one of the historical prototypes defining the concept of episomes (2). Lambda has played a central role in studies defining current concepts of gene regulation and genetic regulatory circuitry.

More recently, lambda strains were used to refine concepts of how cloning and expression vectors should work, and lambda vectors are still commonly used in the construction of genomic libraries (see, for example, Stratagene's Lambda gt11 Vector listing), and the cohesive ends of the lambda genome (cos sites) are used in the construction of cosmids. Lambda and its genes continue to be used in the development of new recombinant DNA technology.

Morphology & classification
Bacteriophage lambda is a double-stranded DNA (dsDNA) phage with an isometric head about 50 nm diameter and a flexible tail about 150 nm long (3)(micrograph). Workers who prefer to use a formal classification scheme for viruses place such viruses in the family Siphovirdae. Lambda is a temperate phage, though not all phages so classified are temperate.

Another scheme of classification denotes all phages in the set including lambda that can recombine with one another to yield infectious progeny as "lambdoid phages" (3). The phages classified this way are all dsDNA phages but not all are Siphoviridae. As far as is known, all lambdoid phages are of temperate phage lineage, though some of the known examples are defective for lysogeny.

Relatives
The lambdoid phages include phi80, P22, 434, HK97, 21, 82, 933W, HK022, and others.

Hosts & cultivation of this phage
Generally lambda is grown in K type strains of E. coli, although other strains of coli can serve as hosts. The host receptor to which wild type lambda adsorbs is known to be the maltose binding protein encoded by the E. coli lamB gene. When high expression of this gene product is accomplished by growing the bacteria in maltose, lambda adsorbs to the bacteria with high efficiency via the central tail spike.

Protocols for preparation and assay of lambda stocks, and for other procedures, can be found in several print sources (4).

Genomics

§ The bacteriophage lambda genome has a linear genetic and physical map, sometimes presented in circular representation since the molecule circularizes at the cohesive ends during some stages of virus activity (5).

§ The DNA molecule has single-stranded 12 base pair complementary (sticky) ends (cohesive ends or cos sites) (6).
Listings of restriction sites in the lambda genome are widely available.

§ The genome size is 48,502 base pairs for the strain known as "wild type" (7), this strain has a single basebair deletion compared to Ur-lambda (8).

§ The complete genome sequence is available online (accession number JO2459). [Note: Searches of GenBank for the string "lambda" will yield too many hits, because of the frequent use of this phage as a cloning vector.]

Assembly pathway

In general dsDNA phages are assembled by assembling separately tails and empty head shells, packaging DNA in the head shells, and attaching tails to the filled heads (9).

References
(1) E.M. Lederberg, "Lysogenicity in E, coli K12", Genetics: 36. 560, 1951.
(2) J. Cairns, G.S. Stent, and J.D. Watson, Phage and the origins of molecular biology, Cold Spring Harbor Laboratory, 1966, some immensely readable and entertaining chapters mentioning lambda include A. Lwoff, "The prophage and I", p.88, E. Kellenberger, ""Electron microscopy of developing bacteriophage", p. 116, A.D. Kaiser, "On the physical basis of genetic structure in bacteriophage", p. 150, and J. Weigle, "Story and structure of the lambda transducing phage" p. 226.
(3) R.W. Hendrix, J.W. Roberts, F.W. Stahl, and R.A. Weisberg, eds., Lambda II, Cold Spring Harbor Laboratory, 1983, "Introduction to Lambda", A.D. Hershey and W. Dove, p. 3-12.
(4) W. Arber, L. Enquist, B. Hohn, N.E. Murray, and K. Murray, in Lambda II, op. cit., "Experimental methods for use with lambda", p. 433.
R.W. Davis, D. Botstein, and J.R. Roth, Advanced Bacterial Genetics: A manual for genetic engineering, Cold Spring Harbor Laboratory Press, 1980.
(5) G.R. Smith, in Lambda II, op. cit., "General Recombination", p. 176.
(6) D.L.Daniels, et. al., in Lambda II, op. cit., Appendix I "A molecular map of coliphage lambda", p. 469.
(7) D.L. Daniels, et. al. in Lambda II, op. cit., Appendix II "Complete annotated lambda sequence", p. 519.
(8) R.W. Hendrix and R.L. Duda, "Lambda PaPa: not the mother of all lambda phages", Science 258(5085): 1145-8, 1992.
(9) S. Casjens and R. Hendrix, "Control mechanisms in dsDNA bacteriophage assembly", in The Bacteriophages, volume 1, ed. R. Calendar, Plenum Press, 1988, p. 15-91.