Article

Rex-centric mutualism.

Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
Journal of Bacteriology (Impact Factor: 3.19). 03/2002; 184(3):857-8. DOI: 10.1128/JB.184.3.857-858.2002
Source: PubMed

ABSTRACT We asked whether Rex exclusion encoded by a lambda prophage confers a protective or a cell-killing phenotype. We found that the Rex system can channel lysogenic cells into an arrested growth phase that gives an overall protective ability to the host despite some associated killing.

0 Bookmarks
 · 
62 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: High relatedness among interacting individuals has generally been conside- red a precondition for the evolution of altruism. However, kin-selection theory also predicts the evolution of altruism when relatedness is low, as long as the cost of the altruistic act is minor compared with its benefit. Here, we demonstrate evidence for a low-cost altruistic act in bacteria. We investigated Escherichia coli responding to the attack of an obligately lytic phage by committing suicide in order to prevent parasite transmission to nearby relatives. We found that bacterial suicide provides large benefits to survivors at marginal costs to committers. The cost of suicide was low, because infected cells are moribund, rapidly dying upon phage infection, such that no more opportunity for reproduction remains. As a consequence of its marginal cost, host suicide was selectively favoured even when related- ness between committers and survivors approached zero. Altogether, our findings demonstrate that low-cost suicide can evolve with ease, represents an effective host-defence strategy, and seems to be widespread among microbes. Moreover, low-cost suicide might also occur in higher organisms as exemplified by infected social insect workers leaving the colony to die in isolation.
    Proceedings of the Royal Society B: Biological Sciences 05/2013; 280:20123035. · 5.68 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The cI-rexA-rexB operon of bacteriophage lambda confers 2 phenotypes, Imm and Rex, to lysogenic cells. Immunity to homoimmune infecting lambda phage depends upon the CI repressor. Rex exclusion of T4rII mutants requires RexA and RexB proteins. Both Imm and Rex share temperature-sensitive conditional phenotypes when expressed from cI[Ts]857 but not from cI+ lambda prophage. Plasmids were made in which cI-rexA-rexB was transcribed from a non-lambda promoter, pTet. The cI857-rexA-rexB plasmid exhibited Ts conditional Rex and CI phenotypes; the cI+-rexA-rexB plasmid did not. Polarity was observed within cI-rexA-rexB transcription at sites in cI and rexA when CI was nonfunctional. Renaturation of the Ts CI857 repressor, allowing it to regain functionality, suppressed the polar effect on downstream transcription from the site in cI. The second strong polar effect near the distal end of rexA was observed for transcription initiated from pE. The introduction of a rho Ts mutation into the host genome suppressed both polar effects, as measured by its suppression of the conditional Rex phenotype. Strong suppression of the conditional Rex[Ts] phenotype was imparted by ssrA and clpP (polar for clpX) null mutations, suggesting that RexA or RexB proteins made under conditions of polarity are subject to 10Sa RNA tagging and ClpXP degradation.
    Canadian Journal of Microbiology 02/2005; 51(1):37-49. · 1.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A new set of lambdoid phages (mEp) classified into different immunity groups was previously described. Phages mEp213, mEp237, and mEp410 were unable to grow in mEp167 lysogenic cells, presumably due to an exclusion mechanism expressed constitutively by the mEp167 repressed prophage. In this work, to analyze the exclusion phenomenon, we constructed a genomic library from mEp167 phage in a pPROEX derivative plasmid. A DNA fragment containing an open reading frame for a 77 amino acid polypeptide was selected by its ability to confer resistance to heteroimmune phage infection. This ORF shows high amino acid sequence identity with putative Cor proteins of phages HK022, phi80 and N15. Cells expressing the mEp167 cor gene from a plasmid (Cor(+) phenotype) excluded 13 of 20 phages from different infection immunity groups. This exclusion was observed in both tonB(-) and tonB(+) cells. Lambdoid mEp phages that were excluded in these cells were unable to infect cells defective in the outer membrane FhuA receptor (fhuA(-)). Thus, Cor-mediated exclusion was only observed in fhuA(+) cells. Phage production after DNA transfection or the spontaneous induction of mEp prophage in Cor(+) cells was not blocked. In addition, ferrichrome uptake, which is mediated by FhuA, was inhibited in Cor(+) cells. Our results show that not only phage infection via FhuA but also a FhuA transport activity (ferrichrome uptake) are inhibited by Cor, presumably by inactivation of FhuA.
    Virology 12/2004; 329(2):425-33. · 3.37 Impact Factor

Full-text (2 Sources)

View
12 Downloads
Available from
Jun 4, 2014