The N protein of bacteriophage lambda is a positive regulator of early lambda gene expression. In a lambdatrp transducing phage, lambdatrp46Nam, the synthesis of trp enzymes in vivo is also dependent on the presence of active N protein. The DNA of this phage has been used in a protein-synthesizing system in vitro to develop a biochemical assay for the activity of the N protein. From the followi...

Transgenic mice suitable for the in vivo assay of suspected mutagens at the chromosome level have been constructed by stable integration of a lambda phage shuttle vector. The shuttle vector, which contains a beta-galactosidase (beta-gal) target gene, can be rescued from genomic DNA with in vitro packaging extracts. Mutations in the target gene are detected by a change in lambda phage plaque col...

Bacteriophage phi 80 and lambda-phi 80 hybrid phage of the type lambda (QSR)80, in which the rightmost 10% of the lambda genome is replaced by corresponding phi 80 material, are unable to grow lytically in himA and hip/himD mutants of Escherichia coli K12 at 32 degrees. The genetic element responsible for the growth defect, rha, has been mapped to the (QSR)80 region and was located more precise...

N15 is a temperate bacteriophage that forms stable lysogens in Escherichia coli. While its virion is morphologically very similar to phage lambda and its close relatives, it is unusual in that the prophage form replicates autonomously as a linear DNA molecule with closed hairpin telomeres. Here, we describe the genomic architecture of N15, and its global pattern of gene expression, which reveal...

A mutant of E. coli (designated the STS mutant) has been isolated in which the phage induction and error-prone DNA repair pathways appear to be expressed constitutively without the cells having received an inducing signal. Phage lambda was not able to lysogenize this mutant, whereas a noninducible mutant of lambda, lambdacIind-, known to synthesize a repressor that is insensitive to the inducti...

Electron microscopy of disrupted Escherichia coli cells under certain conditions revealed loops of a fiber 120 A in diameter which were attached to the cell envelope and showed a 130 A repeating beaded substructure. These fibers were detected only when the cells were lysed in 0.15 M NaCl solutions directly on the electron microscope supporting films and if the dehydration steps began within 2 m...

A factor which inactivates the phage lambda can be extracted from Escherichia coli. This factor is a protein and is located in the outer membrane of the bacterial envelope. It is found in extracts of strains which are sensitive to phage lambda, but not in extracts of strains specifically resistant to this phage. We conclude that this factor is the lambda receptor, responsible for the specific a...

A 2400 base pair DNA segment containing the leftward operator (OL) of phage lambda was covalently joined in vitro to a fragment of simian virus 40 (SV40) DNA harboring the SV40 replication origin. The recombinant molecule was propagated in the presence of helper wild-type SV40 DNA in monkey kidney cells and partially cloned by an infectious center procedure. After propagation in monkey cells an...

Cosmids are plasmids that contain the phage lambda sequences (cos) required for packaging of the phage DNA into the virion. Induction of a lambda prophage in an Escherichia coli strain carrying a cosmid results in lysates containing phage particles that are filled with cosmid DNA. However, the lysates also contain a large excess of infectious phage particles which complicate use of the packaged...

Chi's are genetic elements that stimulate generalized recombination in their locale in phage lambda. All Chi's wherever located on lambda's chromosome, act asymmetrically in crosses blocked in DNA replication: (1) They stimulate exchange primarily to their left on the conventional lambda map, and (2) the stimulated exchange is frequently nonreciprocal, the recombinant carrying the Chi element b...