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Accueil > Départements > Microbiologie > Michael DUBOW : Génomique et Biodiversité microbienne des biofilms

pubmed Vergnaud-Pourcel

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pubmed query = (Vergnaud, Gilles[Author - Full]) OR Pourcel, christine[Author - Full]

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  • Recovery and Characterization of Bacteria Resisting Infection by Lytic Bacteriophage.

    20 novembre, par Latino L, Pourcel C
    Related Articles

    Recovery and Characterization of Bacteria Resisting Infection by Lytic Bacteriophage.

    Methods Mol Biol. 2018;1693:85-98

    Authors: Latino L, Pourcel C

    Abstract
    Bacteria and bacteriophages coexist and coevolve, bacteriophages being obligatory predators exerting an evolutionary pressure on their prey. Mechanisms in action vary depending on the bacterial genomic content and on the regulation of the bacteriophage cycle. To assess the multiplicity of bacterial genes involved in resistance as well as the changes in the bacteriophage interactions with the bacteria, it is necessary to isolate and investigate large numbers of independent resistant variants. Here we describe protocols that have been applied to the study of Pseudomonas aeruginosa and four of its virulent bacteriophages belonging to the Podoviridae and Myoviridae bacteriophage families. Mutations are identified using whole genome sequencing of resistant variants. Phenotypic analyses are performed to describe the changes conferred by the mutations.

    PMID: 29119434 [PubMed - in process]

  • Russian isolates enlarge the known geographic diversity of Francisella tularensis subsp. mediasiatica.

    6 septembre, par Timofeev V, Bakhteeva I, Titareva G, Kopylov P, Christiany D, Mokrievich A, Dyatlov I, Vergnaud G

    Russian isolates enlarge the known geographic diversity of Francisella tularensis subsp. mediasiatica.

    PLoS One. 2017;12(9):e0183714

    Authors: Timofeev V, Bakhteeva I, Titareva G, Kopylov P, Christiany D, Mokrievich A, Dyatlov I, Vergnaud G

    Abstract
    Francisella tularensis, a small Gram-negative bacterium, is capable of infecting a wide range of animals, including humans, and causes a plague-like disease called tularemia-a highly contagious disease with a high mortality rate. Because of these characteristics, F. tularensis is considered a potential agent of biological terrorism. Currently, F. tularensis is divided into four subspecies, which differ in their virulence and geographic distribution. Two of them, subsp. tularensis (primarily found in North America) and subsp. holarctica (widespread across the Northern Hemisphere), are responsible for tularemia in humans. Subsp. novicida is almost avirulent in humans. The fourth subspecies, subsp. mediasiatica, is the least studied because of its limited distribution and impact in human health. It is found only in sparsely populated regions of Central Asia. In this report, we describe the first focus of naturally circulating F. tularensis subsp. mediasiatica in Russia. We isolated and characterized 18 strains of this subspecies in the Altai region. All strains were highly virulent in mice. The virulence of subsp. mediasiatica in a vaccinated mouse model is intermediate between that of subsp. tularensis and subsp. holarctica. Based on a multiple-locus variable number tandem repeat analysis (MLVA), we show that the Altaic population of F. tularensis subsp. mediasiatica is genetically distinct from the classical Central Asian population, and probably is endemic to Southern Siberia. We propose to subdivide the mediasiatica subspecies into three phylogeographic groups, M.I, M.II and M.III.

    PMID: 28873421 [PubMed - in process]

  • A carrier state is established in Pseudomonas aeruginosa by phage LeviOr01, a newly isolated ssRNA levivirus.

    5 août, par Pourcel C, Midoux C, Vergnaud G, Latino L
    Related Articles

    A carrier state is established in Pseudomonas aeruginosa by phage LeviOr01, a newly isolated ssRNA levivirus.

    J Gen Virol. 2017 Aug 04;:

    Authors: Pourcel C, Midoux C, Vergnaud G, Latino L

    Abstract
    ssRNA bacteriophages are very abundant but poorly studied, particularly in relation to their effect on bacterial evolution. We isolated a new Pseudomonas aeruginosa levivirus, vB_PaeL_PcyII-10_LeviOr01, from hospital waste water. Its genome comprises 3669 nucleotides and encodes four putative proteins. Following bacterial infection, a carrier state is established in a fraction of the cells, conferring superinfection immunity. Such cells also resist other phages that use type IV pili as a receptor. The carrier population is composed of a mixture of cells producing phage, and susceptible cells that are non-carriers. Carrier cells accumulate phage until they burst, releasing large quantities of virions. The continuous presence of phage favours the emergence of host variants bearing mutations in genes involved in type IV pilus biogenesis, but also in genes affecting lipopolysaccharide (LPS) synthesis. The establishment of a carrier state in which phage particles are continuously released was previously reported for some dsRNA phages, but has not previously been described for a levivirus. The present results highlight the importance of the carrier state, an association that benefits both phages and bacteria and plays a role in bacterial evolution.

    PMID: 28771128 [PubMed - as supplied by publisher]

  • Fine structure analysis of lipopolysaccharides in bacteriophage-resistant Pseudomonas aeruginosa PAO1 mutants.

    7 juillet, par Latino L, Caroff M, Pourcel C

    Fine structure analysis of lipopolysaccharides in bacteriophage-resistant Pseudomonas aeruginosa PAO1 mutants.

    Microbiology. 2017 Jun;163(6):848-855

    Authors: Latino L, Caroff M, Pourcel C

    Abstract
    Pseudomonas aeruginosa lipopolysaccharides (LPS) serve as primary receptors for many bacteriophages and, consequently, their biosynthesis is frequently affected in phage-resistant mutants. We previously isolated phage-resistant PAO1 mutants using three different phages, and showed that they were affected in the synthesis of LPS. Here we have investigated in detail the effect of mutations in seven genes involved in different steps of the production of core and oligosaccharide chains. The band profile of purified LPS was analysed by PAGE, and we further characterized the O-chains and core structures by MALDI mass spectrometry (MS). Mild LPS extraction conditions and native LPS MS analyses helped unveil lipid A molecular species with three phosphate residues in the close vicinity of the already highly charged inner-core region. No other MS direct analysis has allowed this peculiarity to be demonstrated for native lipid A high-molecular-weight molecular species, in normal growth conditions and without involving separation techniques. The present results shed light on the possible interactions between the phages and the LPS structures in the early phase of infection.

    PMID: 28682742 [PubMed - in process]

  • Correction : Comparison of French and Worldwide Bacillus anthracis Strains Favors a Recent, Post-Columbian Origin of the Predominant North-American Clade.

    28 juin, par Vergnaud G, Girault G, Thierry S, Pourcel C, Madani N, Blouin Y

    Correction: Comparison of French and Worldwide Bacillus anthracis Strains Favors a Recent, Post-Columbian Origin of the Predominant North-American Clade.

    PLoS One. 2017;12(6):e0180603

    Authors: Vergnaud G, Girault G, Thierry S, Pourcel C, Madani N, Blouin Y

    Abstract
    [This corrects the article DOI: 10.1371/journal.pone.0146216.].

    PMID: 28654701 [PubMed - in process]