Involvement of horizontal gene transfer in the emergence of new pathotypes of Ralstonia solanacearum : [Abstract of poster]

Ralstonia solanacearum is a widely distributed phytopathogenic bacterium that is known to invade more than 200 host species, mainly in tropical areas. R. solanacearum has been described as a highly flexible organism capable of counteracting plant resistance, leading to the emergence of a new pathological variant. We propose to investigate the fundamental role of horizontal gene transfer (HGT) in its genome evolution. In the R. solanacearum species complex, the natural ability to transform has been described as an ubiquitous physiological trait. Eighty percent of strains distributed in all phylotypes - likely species - have the ability to acquire free plasmids and/or genomic DNA (Coupat et al., 2008, FEMS Microbiol Ecol 66:14-24). Extent and number of transfer events were also evaluated by using selective antibiotics markers as well as by comparative genomic hybridization with DNA microarrays. Results showed that replacements might involve DNA fragments up to 90 kb and multiple integration events into the R. solanacearum genome. In addition, inter-phylotype HGT studies showed that transformants were able to acquire large DNA blocks (30 kb) containing pathogenicity determinants from the DNA donor (Guidot et al., 2009, ISME J. doi :1038/ismej.2009.14). The natural transformation mechanism thus appears as one of the main forces for the generation of emergent pathogens. We confirmed that a recombinant strain, which was found to be more virulent on tomato than its wild type parental strain, has acquired a type III effector which was not present in the wild type parental genome. (Texte intégral

Les maladies pyogènes du dromadaire en Ethiopie. Symptomatologie. Etiologie

L'étude des maladies pyogènes du dromadaire en Ethiopie permet de dégager deux entités cliniques assez définies: le mala ou forme ganglionnaire et le maha ou doula ou nécrose cutanée. Le mala principale maladie pyogène, est dû à Corynebacterium pseudotuberculosi s et Streptococcus groupe B de Lancefield. C'est une affection chronique, se traduisant par des abcès ganglionnaires à la base du cou et sur la croupe. Les streptocoques B et les staphylocoques dominent dans l'étiologie du maha, maladie cutanée à abcès plats évoluant vers l'ulcération. Les autres affections pyogènes externes sont des infections localisées, liées à des traumatismes divers, et pour lesquelles sont isolés: streptocoque B (47 p. 100 des cas), Corynebacterium pyogenes (12,2 p. 100), staphylocoques (14 p. 100), bactéries du type Lactobacillus et, rarement Corynebacterium pseudotuberculosis, ainsi qu'un actinomycète présentant les caractères de Dermatophilus congolensi

Ralstonia solanacearum, a widespread bacterial plant pathogen in the post-genomic era

Ralstonia solanacearum is a soil-borne bacterium causing the widespread disease known as bacterial wilt. Ralstonia solanacearum is also the causal agent of Moko disease of banana and brown rot of potato. Since the last R. solanacearum pathogen profile was published 10 years ago, studies concerning this plant pathogen have taken a genomic and post-genomic direction. This was pioneered by the first sequenced and annotated genome for a major plant bacterial pathogen and followed by many more genomes in subsequent years. All molecular features studied now have a genomic flavour. In the future, this will help in connecting the classical field of pathology and diversity studies with the gene content of specific strains. In this review, we summarize the recent research on this bacterial pathogen, including strain classification, host range, pathogenicity determinants, regulation of virulence genes, type III effector repertoire, effector-triggered immunity, plant signalling in response to R. solanacearum, as well as a review of different new pathosystems

Method for detecting Ralstonia solanacearum race 3 biovar 2

The invention concerns a method for the detection of Ralstonia solanacearum race 3 biovar 2 strains in a medium, comprising the determination of the presence or the absence in a sample of the medium, of: (i) at least one first nucleic acid target having a sequence selected from the group constituted of SEQ ID NO: 1-49, complementary sequences thereof, and homologous sequences thereof, or (ii) at least one fragment of said first target nucleic acid, wherein said fragment is not constituted of or comprised in a sequence selected from the group constituted of SEQ ID NO: 111-140; whereby, if said first nucleic acid target or fragment thereof is present in the sample, it is determined that Ralstonia solanacearum race 3 biovar 2 strain is present in the medium. (Resumé d'auteur

Aging promotes pro-fibrotic matrix production and increases fibrocyte recruitment during acute lung injury.

Fibrotic lung diseases increase with age. Previously we determined that senescence increases tissue expression of fibronectin EDA (Fn-EDA) and decreases fibroblast expression of Thy-1, and that fibrocytes contribute to fibrosis following bleomycin-induced lung injury in mice. In this study we hypothesized that fibroblasts lacking Thy-1 expression produce an extracellular matrix that promotes fibrocyte retention and myofibroblast transdifferentiation, thereby promoting fibrogenesis. Young and old mice were treated with bleomycin intratracheally; fibrocytes in the bone marrow, blood, and lungs were quantified, and lung fibroblast Thy-1 expression assessed. Bone marrow-derived fibrocytes were cultured on matrices derived from Thy-1(+) or Thy-1(-) fibroblasts ± the pro-fibrotic cytokine TGFβ1. Older mice had more fibrocytes in their bone marrows at baseline and more fibrocytes in their lungs following bleomycin treatment. In parallel, lung fibroblasts in older mice had lower expression of Thy-1 at baseline that increased transiently 7 days after bleomycin treatment but then rapidly waned such that 14 days after bleomycin treatment Thy-1 expression was again markedly lower. Fibrocytes cultured on matrices derived from Thy-1(-) fibroblasts + TGFβ1 had increased gene expression for collagen type 1, fibronectin, Fn-EDA, and α-smooth muscle actin. In parallel, whereas the matrices derived from Thy-1(-) fibroblasts stimulated phosphorylation of Akt in cultured fibrocytes, the matrices derived from Thy-1(+) fibroblasts induced apoptosis. These findings suggest that senescence increases fibrocyte recruitment to the lung following injury and that loss of Thy-1 expression by lung fibroblasts promotes fibrocyte retention and myofibroblast trans-differentiation that renders the "aging lung" susceptible to fibrosis

Les “Enfances Guillaume” dans le “Roman de Guillaume d’Orange”: distinction, délicatesse, finesse d’esprit

The Roman de Guillaume d’Orange most often frees itself from any specific influence coming from the songs contained in the Cycle: this is particularly true in the chapters corresponding to the Enfances Guillaume. The reworking makes ample room for interior life and new traits closely tied to the conception of a refined society. Our objective is to examine the rewriting for its own sake: inspiration and mentalities, the influence of contemporary mores, the conception of characters and the romance universe, and the tonality of the narrative, which is characterized by refinement, subtlety and finesse

Alain Labbé

Alain Labbé nous a quittés pendant la nuit des Rameaux de cette année 2004. Ce fut une immense tristesse. La nouvelle me parvint dans les premières heures du lundi 5 avril. Je venais d’arriver à Malte et, aussitôt, le soleil printanier de la belle île méditerranéenne m’apparut voilé. La séduisante architecture de La Valette – dont Alain m’avait parlé avec la chaleur rassurante qui lui était habituelle – et la splendide cathédrale Saint-Jean que je venais de visiter, aux somptueuses décoration..

Environmental toxicity, redox signaling and lung inflammation:the role of glutathione

Glutathione (γ-glutamyl-cysteinyl-glycine, GSH) is the most abundant intracellular antioxidant thiol and is central to redox defense during oxidative stress. GSH metabolism is tightly regulated and has been implicated in redox signaling and also in protection against environmental oxidant-mediated injury. Changes in the ratio of the reduced and disulfide form (GSH/GSSG) can affect signaling pathways that participate in a broad array of physiological responses from cell proliferation, autophagy and apoptosis to gene expression that involve H(2)O(2) as a second messenger. Oxidative stress due to oxidant/antioxidant imbalance and also due to environmental oxidants is an important component during inflammation and respiratory diseases such as chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, acute respiratory distress syndrome, and asthma. It is known to activate multiple stress kinase pathways and redox sensitive transcription factors such as Nrf2, NF-κB and AP-1, which differentially regulate the genes for pro-inflammatory cytokines as well as the protective antioxidant genes. Understanding the regulatory mechanisms for the induction of antioxidants, such as GSH, versus pro-inflammatory mediators at sites of oxidant-directed injuries may allow for the development of novel therapies which will allow pharmacological manipulation GSH synthesis during inflammation and oxidative injury. This article features the current knowledge about the role of GSH in redox signaling, GSH biosynthesis and particularly the regulation of transcription factor Nrf2 by GSH and downstream signaling during oxidative stress and inflammation in various pulmonary diseases. We also discussed the current therapeutic clinical trials using GSH and other thiol compounds, such as N-acetyl-L-cysteine, fudosteine, carbocysteine, erdosteine in environment-induced airways disease

Functional diversification of the GALA type III effector family contributes to Ralstonia solanacearum adaptation on different plant hosts

Type III effectors from phytopathogenic bacteria exhibit a high degree of functional redundancy, hampering the evaluation of their precise contribution to pathogenicity. This is illustrated by the GALA type III effectors from Ralstonia solanacearum, which have been shown to be collectively, but not individually, required for disease on Arabidopsis thaliana and tomato. We investigated evolution, redundancy and diversification of this family in order to understand the individual contribution of the GALA effectors to pathogenicity.From sequences available, we reconstructed GALA phylogeny and performed selection studies. We then focused on the GALAs from the reference strain GMI1000 to examine their ability to suppress plant defense responses and contribution to pathogenicity on three different host plants: A. thaliana, tomato (Lycopersicum esculentum) and eggplant (Solanum melongena).The GALA family is well conserved within R. solanacearum species. Patterns of selection detected on some GALA family members, together with experimental results, show that GALAs underwent functional diversification.We conclude that functional divergence of the GALA family likely accounts for its remarkable conservation during R. solanacearum evolution and could contribute to R. solanacearum’s adaptation on several host plants