Lambda phage

About: Lambda phage is a research topic. Over the lifetime, 1609 publications have been published within this topic receiving 84675 citations. The topic is also known as: Enterobacteria phage lambda.

An action spectrum of the riboflavin-photosensitized inactivation of Lambda phage.

Abstract: The Action Spectrum of riboflavin (RB) sensitized inactivation of lambda phage was determined between 266 and 575 nm. Below 304 nm, RB depresses the phage reduction by screening phage from radiation that it would otherwise absorb directly. Between 308 and 525 nm, RB sensitizes the inactivation of phage. Enhanced phage reduction is observed at 320 and 500 nm because of binding of RB to the phage and the shifting of the absorption curve of the phage-bound flavin relative to free flavin in phosphate-buffered saline. Enhanced inactivation at 320 and 500 nm and depressed phage inactivation between 360 and 410 nm is also influenced by the inner filter effect.

Construction from Mu d1 (lac Apr) lysogens of lambda bacteriophage bearing promoter-lac fusions: isolation of lambda ppheA-lac.

Abstract: Bacteriophage Mu d1 (lac Aprr) was used to obtain strains of Escherichia coli K-12 in which the lac genes are expressed from the promoter of pheA, the structural gene for the enzyme chorismate mutase P-prephenate-dehydratase. A derivative of bacteriophage lambda which carries the pheA-lac fusion was prepared; the method used is generally applicable for the construction, from Mu dl lysogens, of specialized transducing lambda phage carrying the promoter-lac fusions. A restriction enzyme cleavage map of lambda ppheA-lac for the enzymes HindIII and PstI is presented.

Posttranscriptional Control of the Lysogenic Pathway in Bacteriophage Lambda

Abstract: Publisher Summary This chapter discusses the recent developments in the study of Lambda (λ) phage gene expression showing that post-transcriptional control of phage genes by host functions provides highly sensitive regulatory circuits. The control of transcription initiation from the early promoters of bacteriophage λ is not sufficient to provide for subtle controls involved with the switch between lysogenic and lytic pathways. The ability of λ to choose between lytic and lysogenic development has evolved as a response to changes in the physiological state of the host cell. The frequency by which the phage enters the lytic or lysogenic pathway is determined in large measure by the nutritional state of the host cell. For example, starved cells lysogenize more efficiently than cells grown in a rich medium. In addition, the number of infecting phage particles per cell is also known to determine the rate of lysogenization: the higher the multiplicity of infection, the higher the rate of lysogenization. It is probable that the physiological state of the cell is signaled to the phage by host regulatory factors.

Identification and characterization of a gene responsible for inhibiting propagation of methylated DNA sequences in mcrA mcrB1 Escherichia coli strains.

Abstract: Identifying and eliminating endogenous bacterial enzyme systems can significantly increase the efficiency of propagation of eukaryotic DNA in Escherichia coli. We have recently examined one such system which inhibits the propagation of lambda DNA rescued from transgenic mouse tissues. This rescue procedure utilizes lambda packaging extracts for excision of the lambda DNA from the transgenic mouse genome, as well as E. coli cells for subsequent infection and propagation. This assay, in combination with conjugal mating, P1 transduction, and gene cloning, was used to identify and characterize the E. coli locus responsible for this difference in efficiency. It was determined that the E. coli K-12 mcrB gene when expressed on a high-copy-number plasmid can cause a decrease in rescue efficiency despite the presence of the mcrB1 mutation, which inactivates the classic McrB restriction activity. (This mutation was verified by sequence analysis.) However, this McrB1 activity is not observed when the cloned mcrB1 gene is inserted into the E. coli genome at one copy per chromosome. A second locus was identified which causes a decrease in rescue efficiency both when expressed on a high-copy-number plasmid and when inserted into the genome. The data presented here suggest that this locus is mrr and that the mrr gene product can recognize and restrict cytosine-methylated sequences. Removal of this DNA region including the mrr gene from E. coli K-12 strains allows high rescue efficiencies equal to those of E. coli C strains. These modified E. coli K-12 plating strains and lambda packaging extract strains should also allow a significant improvement in the efficiency and representation of eukaryotic genomic and cDNA libraries.