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.

Mapping of integration and excision crossovers in superinfection double lysogens for phage lambda in escherichia coli

Abstract: I N a previous paper it was shown that one prophage apparently acts as a homology region for a superinfecting phage of the same kind (CALEF, MARCHELLI, GUERRINI 1965). A more rigorous test for the same possibility can be obtained by correlating the frequency of integration of superinfecting phage at any given region with the map length of that region. The work presented here consists primarily in a genetic mapping of the prophages in a double lysogen. The mapping was meant to verify that the process of integration of the second prophage into a segment of the first, under conditions which inhibit its function (homoimmunity), occurs at a frequency related to the length of the segment involved. Concomitantly we were able to verify a number of features of the virus-host relationships such as linear insertion and order of markers. A series of 19 independent double lysogens of independent origin have been analyzed genetically and are reported in this paper. The analysis has shown a positive correlation between map length and integration at any given segment. Some of the double lysogens, the structure of which had been deduced by PI transduction mapping, were further analyzed by examining their monolysogenic segregants. The data obtainable by this method made it possible to: ( 1 ) map the prophage (confirming the known order of prophage genes), (2) have some insight into the modalities of haploidization, and (3) measure the relative length of those portions of the prophage map which lie outside the two extreme markers.

Stochastic cellular fate decision making by multiple infecting lambda phage.

Abstract: Bacteriophage lambda is a classic system for the study of cellular decision making. Both experiments and mathematical models have demonstrated the importance of viral concentration in the lysis-lysogeny decision outcome in lambda phage. However, a recent experimental study using single cell and single phage resolution reported that cells with the same viral concentrations but different numbers of infecting phage (multiplicity of infection) can have markedly different rates of lysogeny. Thus the decision depends on not only viral concentration, but also directly on the number of infecting phage. Here, we attempt to provide a mechanistic explanation of these results using a simple stochastic model of the lambda phage genetic network. Several potential factors including intrinsic gene expression noise, spatial dynamics and cell-cycle effects are investigated. We find that interplay between the level of intrinsic noise and viral protein decision threshold is a major factor that produces dependence on multiplicity of infection. However, simulations suggest spatial segregation of phage particles does not play a significant role. Cellular image processing is used to re-analyse the original time-lapse movies from the recent study and it is found that higher numbers of infecting phage reduce the cell elongation rate. This could also contribute to the observed phenomena as cellular growth rate can affect transcription rates. Our model further predicts that rate of lysogeny is dependent on bacterial growth rate, which can be experimentally tested. Our study provides new insight on the mechanisms of individual phage decision making. More generally, our results are relevant for the understanding of gene-dosage compensation in cellular systems.

Development and application of an efficient recombineering system for Burkholderia glumae and Burkholderia plantarii

Abstract: The lambda phage Red proteins Redα/Redβ/Redγ and Rac prophage RecE/RecT proteins are powerful tools for precise and efficient genetic manipulation but have been limited to only a few prokaryotes. Here, we report the development and application of a new recombineering system for Burkholderia glumae and Burkholderia plantarii based on three Rac bacteriophage RecET-like operons, RecETheBDU8 , RecEThTJI49 and RecETh1h2eYI23 , which were obtained from three different Burkholderia species. Recombineering experiments indicated that RecEThTJI49 and RecETh1h2eYI23 showed higher recombination efficiency compared to RecETheBDU8 in Burkholderia glumae PG1. Furthermore, all of the proteins currently categorized as hypothetical proteins in RecETh1h2eYI23, RecEThTJI49 and RecETheBDU8 may have a positive effect on recombination in B. glumae PG1 except for the h2 protein in RecETh1h2eYI23 . Additionally, RecETYI23 combined with exonuclease inhibitors Pluγ or Redγ exhibited equivalent recombination efficiency compared to Redγβα in Escherichia coli, providing potential opportunity of recombineering in other Gram-negative bacteria for its loose host specificity. Using recombinase-assisted in situ insertion of promoters, we successfully activated three cryptic non-ribosomal peptide synthetase biosynthetic gene clusters in Burkholderia strains, resulting in the generation of a series of lipopeptides that were further purified and characterized. Compound 7 exhibited significant potential anti-inflammatory activity by inhibiting lipopolysaccharide-stimulated nitric oxide production in RAW 264.7 macrophages. This recombineering system may greatly enhance functional genome research and the mining of novel natural products in the other species of the genus Burkholderia after optimization of a protocol.