Showing papers on "Lambda phage published in 2017"

Display of HIV-1 Envelope Protein on Lambda Phage Scaffold as a Vaccine Platform.

Abstract: The generation of a strong antibody response to target antigens is a major goal for vaccine development. Here we describe the display of the human immunodeficiency virus (HIV) envelope spike protein (Env) on a virus-like scaffold provided by the lambda phage capsid. Phage vectors, in general, have advantages over mammalian virus vectors due to their genetic tractability, inexpensive production, suitability for scale-up, as well as their physical stability, making them an attractive vaccine platform.

Combining Comprehensive Analysis of Off-Site Lambda Phage Integration with a CRISPR-Based Means of Characterizing Downstream Physiology.

Abstract: During its lysogenic life cycle, the phage genome is integrated into the host chromosome by site-specific recombination. In this report, we analyze lambda phage integration into noncanonical sites using next-generation sequencing and show that it generates significant genetic diversity by targeting over 300 unique sites in the host Escherichia coli genome. Moreover, these integration events can have important phenotypic consequences for the host, including changes in cell motility and increased antibiotic resistance. Importantly, the new technologies that we developed to enable this study-sequencing secondary sites using next-generation sequencing and then selecting relevant lysogens using clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9-based selection-are broadly applicable to other phage-bacterium systems.IMPORTANCE Bacteriophages play an important role in bacterial evolution through lysogeny, where the phage genome is integrated into the host chromosome. While phage integration generally occurs at a specific site in the host chromosome, it is also known to occur at other, so-called secondary sites. In this study, we developed a new experimental technology to comprehensively study secondary integration sites and discovered that phage can integrate into over 300 unique sites in the host genome, resulting in significant genetic diversity in bacteria. We further developed an assay to examine the phenotypic consequence of such diverse integration events and found that phage integration can cause changes in evolutionarily relevant traits such as bacterial motility and increases in antibiotic resistance. Importantly, our method is readily applicable to other phage-bacterium systems.

Regulation of Shiga Toxin Production

Abstract: Although Shiga toxins are produced by particular E. coli serotypes, the genes transcribed, as well as the timing and quantity of transcription, are determined by lambdoid phages (phages related to phage λ) that infect those serotypes. A lambdoid phage is referred to as temperate when it integrates into a host cell genome and replicates its DNA “lysogenically” (as the cell replicates its DNA). A stressed cell detects DNA damage and figuratively sends out an “SOS.” The phages have a sophisticated mechanism that detects the host cell SOS response to DNA damage and responds by replicating “lytically” (with lysis of the host cell). Each “Stx-phage” has one Shiga toxin operon, composed of genes encoding the Shiga toxin StxA and StxB subunits. However, an individual Stx-phage may integrate into a bacterial chromosome more than once, and different species of Stx-phage can infect a bacterium simultaneously. Both the multiplicity of infection and recombination events permit a single host to produce more than one type or variant of Shiga toxin, each produced under the control of its own phage. Additional transposable elements (transposons) from the bacterial host add to this genetic diversity, and all levels of this diversity are transmissible to other bacterial hosts. To combat phages, bacterial hosts have a primitive adaptive immune system that employs clustered, regularly-interspaced, short palindromic repeats (CRISPR) and the CRISPR-associated genes (CAS). CRISPR/CAS can inactivate infecting Stx-phages.

Expression system containing phage lysozyme, and applications thereof

Abstract: The present invention relates to an expression system containing lambda phage lysozyme, wherein the rapid and efficient bacterial lysis method and applications thereof are achieved by inducing the expression of lambda phage lysozyme in escherichia coli. According to the present invention, after the strain containing the expression system is subjected to freeze thawing or low concentration chloroform treatment, the treated strain can efficiently cleave escherichia coli cells and release the bacterial protein, and the obtained protein has higher activity compared to the protein obtained by using the commonly used bacterial lysis methods such as ultrasonic wall breaking, egg white lysozyme digestion.