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.

Recombination-deficient deletions in bacteriophage lambda and their interaction with chi mutations.

Abstract: We have isolated a new class of deletion mutants of phage lambda that extend from the prophage attachment site, att, into the gam and cIII genes. In this respect they are similar to certain of the lambda pbio transducing phage, but they differ in having a low burst size and in forming minute plaques. Lytically grown stocks of the deletions contain a variable proportion of phage that produce large plaques. These have been shown to carry an additional point mutation. Similar mutations, called chi, have been described by Lam et al. (1974), who showed that they result in a hot-spot for recombination produced by the host recombination system (Rec). We show that chi mutations can occurat several sites in the lambda genome and produce a Rec-dependent increase in the burst size of the one deletion tested.---In addition to reducing burst size, the one deletion tested reduces synthesis of DNA and emdolysin but increases production of serum blocking protein. A chi mutation partially restores DNA synthesis and endolysin production and reduces serum blocking protein to normal levels. Our results are consistent with the hypothesis put forward by Lam et al., that chi enhances the frequency of Rec-promoted recombination, which provides the only pathway for production of maturable DNAin a red gam infection. The mechanism of the differential effect on protein production is, however, unclear.---Chi mutations are found to occur in DNA other than that of lambda. We show that, as has been suggested elsewhere (McMilin, Stahl and Stahy 1974), the lambda pbio transducing phages carry a chi mutation within the E. coli DNA substitution. A chi mutation also arose in a new substitution of unknown origin isolated in the course of this work.

Characterization of a bacteriophage that carries the genes for production of Shiga-like toxin 1 in Escherichia coli.

Abstract: The Shiga-like toxin 1-converting bacteriophage H-19B was recently shown to carry the structural genes for the toxin and was shown to have DNA sequence homology with phage lambda. We present evidence that the linear genome of bacteriophage H-19B has cohesive termini which become covalently associated during prophage integration. Integration occurs through a site on a 4-kilobase-pair EcoRI fragment located near the center of the bacteriophage chromosome. The relationship between bacteriophages H-19B and lambda was examined by Southern hybridization. Homologous regions were mapped on the respective chromosomes which corresponded to the regions of the J gene, the int-xis area, and the O and P genes of phage lambda. The H-19B tox genes were mapped to the right of the O and P gene homology, which was far away from the phage attachment site. We concluded that H-19B is a lambdoid bacteriophage. Unlike other toxin-converting bacteriophages, the toxin genes were not located adjacent to the phage attachment site. It appeared that the Shiga-like toxin 1 genes were not picked up by a simple imprecise prophage excision. H-19B could, however, have acquired chromosomally located toxin genes by a series of events involving deletion and duplication followed by aberrant excision.

Bacteriophage infection is targeted to cellular poles.

Abstract: The poles of bacteria exhibit several specialized functions related to the mobilization of DNA and certain proteins. To monitor the infection of Escherichia coli cells by light microscopy, we developed procedures for the tagging of mature bacteriophages with quantum dots. Surprisingly, most of the infecting phages were found attached to the bacterial poles. This was true for a number of temperate and virulent phages of E. coli that use widely different receptors and for phages infecting Yersinia pseudotuberculosis and Vibrio cholerae. The infecting phages colocalized with the polar protein marker IcsA-GFP. ManY, an E. coli protein that is required for phage lambda DNA injection, was found to localize to the bacterial poles as well. Furthermore, labelling of lambda DNA during infection revealed that it is injected and replicated at the polar region of infection. The evolutionary benefits that lead to this remarkable preference for polar infections may be related to lambda's developmental decision as well as to the function of poles in the ability of bacterial cells to communicate with their environment and in gene regulation.

Mutant lambda phage repressor with a specific defect in its positive control function

Abstract: The lambda phage repressor is both a positive and a negative regulator of gene transcription. We describe a mutant lambda phage repressor that has specifically lost its activator function. The mutant binds to the lambda phage operator sites and represses the lambda phage promoters PR and PL. However, it fails to stimulate transcription from the promoter PRM. The mutation lies in that portion of repressor--namely, the amino-terminal domain--that has been shown [Sauer, R. T., Pabo, C. O., Meyer, B. J., Ptashne, M. & Backman, K. C. (1979) Nature (London) 279, 396-400] to mediate stimulation of PRM. We suggest that the mutation has altered that region of repressor which, in the wild-type, contacts RNA polymerase to activate transcription from PRM.