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15 mars 2018: 1 événement

  • Département Microbiologie

    Jeudi 15 mars 11:30-13:00 - Dr. Xavier Charpentier - Centre International de Recherche en Infectiologie (CIRI), Lyon

    Silently transformable : how bacteria conceal their built-in capacity of genetic exchange

    Résumé : A highly conserved DNA uptake system allows some bacteria to actively import and integrate exogenous DNA. This process, called natural transformation, represents a major mechanism of horizontal gene transfer (HGT) and is involved in the acquisition of virulence and antibiotic resistance determinants. Despite evidence of widespread HGT and the high level of conservation of the genes coding the DNA uptake system, most bacterial species appear non-transformable under laboratory conditions. This observation led us to investigated the mechanism that controls expression of the DNA uptake system in the human pathogen Legionella pneumophila (1). We found that expression of the DNA uptake system is controlled by a novel RNA-based silencing system. Silencing is relieved under specific conditions, allowing bacteria to take up free DNA and subsequently undergo genetic transformation. RNA-based silencing represents a previously unknown regulatory means to control natural transformation (2). Importantly, these findings also show that a previously overlooked family of chromosome-encoded proteins act as chaperones of trans-acting sRNAs, playing key roles in post-transcriptional gene regulation throughout bacterial species (3). Also, and in light of unpublished results, a recent hypothesis suggesting that natural transformation evolved as mechanism to rid the genome of selfish genetic elements will be discussed.
    1. Attaiech L, Boughammoura A, Brochier-Armanet C, Allatif O, Peillard-Fiorente F, Edwards RA, Omar AR, MacMillan AM, Glover M, Charpentier X. 2016. Silencing of natural transformation by an RNA chaperone and a multitarget small RNA. Proc Natl Acad Sci U S A 113:8813–8818.
    2. Attaiech L, Charpentier X. 2017. Silently transformable : the many ways bacteria conceal their built-in capacity of genetic exchange. Curr Genet 63:451–455.
    3. Attaiech L, Glover JNM, Charpentier X. 2017. RNA Chaperones Step Out of Hfq’s Shadow. Trends Microbiol 25:247–249.

    Invited by Tamara Basta-Le Berre

    Lieu : Salle Kalogeropoulos - Bâtiment 400, Campus d’Orsay

    En savoir plus : Département Microbiologie