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Search Results: 1 - 10 of 3995 matches for " Alain Givaudan "
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Virulence and Pathogen Multiplication: A Serial Passage Experiment in the Hypervirulent Bacterial Insect-Pathogen Xenorhabdus nematophila
élodie Chapuis,Sylvie Pagès,Vanya Emelianoff,Alain Givaudan,Jean-Baptiste Ferdy
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015872
Abstract: The trade-off hypothesis proposes that the evolution of pathogens' virulence is shaped by a link between virulence and contagiousness. This link is often assumed to come from the fact that pathogens are contagious only if they can reach high parasitic load in the infected host. In this paper we present an experimental test of the hypothesis that selection on fast replication can affect virulence. In a serial passage experiment, we selected 80 lines of the bacterial insect-pathogen Xenorhabdus nematophila to multiply fast in an artificial culture medium. This selection resulted in shortened lag phase in our selected bacteria. We then injected these bacteria into insects and observed an increase in virulence. This could be taken as a sign that virulence in Xenorhabdus is linked to fast multiplication. But we found, among the selected lineages, either no link or a positive correlation between lag duration and virulence: the most virulent bacteria were the last to start multiplying. We then surveyed phenotypes that are under the control of the flhDC super regulon, which has been shown to be involved in Xenorhabdus virulence. We found that, in one treatment, the flhDC regulon has evolved rapidly, but that the changes we observed were not connected to virulence. All together, these results indicate that virulence is, in Xenorhabdus as in many other pathogens, a multifactorial trait. Being able to grow fast is one way to be virulent. But other ways exist which renders the evolution of virulence hard to predict.
Plastic architecture of bacterial genome revealed by comparative genomics of Photorhabdus variants
Sophie Gaudriault, Sylvie Pages, Anne Lanois, Christine Laroui, Corinne Teyssier, Estelle Jumas-Bilak, Alain Givaudan
Genome Biology , 2008, DOI: 10.1186/gb-2008-9-7-r117
Abstract: We used a combination of macrorestriction and DNA microarray experiments to perform a comparative genomic study of different P. luminescens TT01 variants. Prolonged culturing of TT01 strain and a genomic variant, collected from the laboratory-maintained symbiotic nematode, generated bacterial lineages composed of primary and secondary phenotypic variants and colonial variants. The primary phenotypic variants exhibit several characteristics that are absent from the secondary forms. We identify substantial plasticity of the genome architecture of some variants, mediated mainly by deletions in the 'flexible' gene pool of the TT01 reference genome and also by genomic amplification. We show that the primary or secondary phenotypic variant status is independent from global genomic architecture and that the bacterial lineages are genomic lineages. We focused on two unusual genomic changes: a deletion at a new recombination hotspot composed of long approximate repeats; and a 275 kilobase single block duplication belonging to a new class of genomic duplications.Our findings demonstrate that major genomic variations occur in Photorhabdus clonal populations. The phenotypic consequences of these genomic changes are cryptic. This study provides insight into the field of bacterial genome architecture and further elucidates the role played by clonal genomic variation in bacterial genome evolution.Comparative genomics, in the study of different bacterial genera, species, and strains, leads to the definition of two DNA pools in bacterial genomes: a set of genes shared by all genomes in a taxa, namely the 'core' genome; and a set of genes containing mobile and accessory genetic elements, termed the 'flexible' gene pool. Both intergenomic and intragenomic rearrangements occur in this 'flexible' gene pool [1]. Changes in the 'flexible' gene pool are considered to be the motor of bacterial diversification and evolution [2-4].However, comparative genomic analyses of genomic variants with
FliZ Is a Global Regulatory Protein Affecting the Expression of Flagellar and Virulence Genes in Individual Xenorhabdus nematophila Bacterial Cells
Grégory Jubelin equal contributor,Anne Lanois equal contributor,Dany Severac,Stéphanie Rialle,Cyrille Longin,Sophie Gaudriault,Alain Givaudan
PLOS Genetics , 2013, DOI: 10.1371/journal.pgen.1003915
Abstract: Heterogeneity in the expression of various bacterial genes has been shown to result in the presence of individuals with different phenotypes within clonal bacterial populations. The genes specifying motility and flagellar functions are coordinately regulated and form a complex regulon, the flagellar regulon. Complex interplay has recently been demonstrated in the regulation of flagellar and virulence gene expression in many bacterial pathogens. We show here that FliZ, a DNA-binding protein, plays a key role in the insect pathogen, Xenorhabdus nematophila, affecting not only hemolysin production and virulence in insects, but efficient swimming motility. RNA-Seq analysis identified FliZ as a global regulatory protein controlling the expression of 278 Xenorhabdus genes either directly or indirectly. FliZ is required for the efficient expression of all flagellar genes, probably through its positive feedback loop, which controls expression of the flhDC operon, the master regulator of the flagellar circuit. FliZ also up- or downregulates the expression of numerous genes encoding non-flagellar proteins potentially involved in key steps of the Xenorhabdus lifecycle. Single-cell analysis revealed the bimodal expression of six identified markers of the FliZ regulon during exponential growth of the bacterial population. In addition, a combination of fluorescence-activated cell sorting and RT-qPCR quantification showed that this bimodality generated a mixed population of cells either expressing (“ON state”) or not expressing (“OFF state”) FliZ-dependent genes. Moreover, studies of a bacterial population exposed to a graded series of FliZ concentrations showed that FliZ functioned as a rheostat, controlling the rate of transition between the “OFF” and “ON” states in individuals. FliZ thus plays a key role in cell fate decisions, by transiently creating individuals with different potentials for motility and host interactions.
Impact of Toxic Cyanobacterial Blooms on Eurasian Perch (Perca fluviatilis): Experimental Study and In Situ Observations in a Peri-Alpine Lake
Beno?t Sotton, Jean Guillard, Sylvie Bony, Alain Devaux, Isabelle Domaizon, Nicolas Givaudan, Fran?ois Crespeau, Hélène Huet, Orlane Anneville
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0052243
Abstract: Due to the importance of young-of-the-year (YOY) perch in the peri-alpine regions where they are consumed, the microcystin (MC) contamination of YOY perch was analysed both in field (Lake Bourget, France) and experimentally using force-feeding protocols with pure MCs. In-situ, schools of YOY perch present in the epilimnion of the lake were never found in direct contact with the P. rubescens blooms that were present in the metalimnion. However, MCs were detected in the muscles and liver of the fish and were thus assumed to reach YOY perch through dietary routes, particularly via the consumption of MC-containing Daphnia. Force-feeding experiment demonstrates the existence of MC detoxification/excretion processes and suggests that in situ, YOY perch could partly detoxify and excrete ingested MCs, thereby limiting the potential negative effects on perch populations under bloom conditions. However, because of chronic exposure these processes could not allow for the complete elimination of MCs. In both experimental and in situ studies, no histological change was observed in YOY perch, indicating that MC concentrations that occurred in Lake Bourget in 2009 were too low to cause histological damage prone to induce mortality. However, Deoxyribonucleic acid (DNA) damages were observed for both the high and low experimental MC doses, suggesting that similar effects could occur in situ and potentially result in perch population disturbance during cyanobacterial blooms. Our results indicate the presence of MCs in wild perch, the consumption of this species coming from Lake Bourget is not contested but more analyses are needed to quantify the risk.
Evaluación del programa escolarizado para adolescentes: "un equipo contra el VIH/SIDA"
Martha Givaudan,Susan Pick
Revista Interamericana de Psicología , 2005,
Abstract: Se reporta el desarrollo, instrumentación y evaluación longitudinal de un programa de prevención temprana de VIH/SIDA para adolescentes. El estudio se llevó a cabo en Toluca, México. La intervención consta de un componente de capacitación para docentes quienes replican posteriormente el programa con sus alumnos y alumnas en un ambiente escolarizado. La muestra estuvo constituida por 2064 adolescentes mujeres y hombres en su mayoría sin experiencia sexual. Se analizaron los resultados del efecto de las variables precursoras de conducta sexual protegida (conocimientos, actitudes y confianza para obtener y usar condones) a través de un análisis de varianza que incluyeron cuatro mediciones comparadas con un grupo control. Después de un a o de seguimiento, se encontraron diferencias estadísticamente significativas en todas las variables analizadas al comparar el grupo experimental y el grupo control. No hubo incremento en la incidencia de relaciones sexuales
Cycle Inhibiting Factors (CIFs) Are a Growing Family of Functional Cyclomodulins Present in Invertebrate and Mammal Bacterial Pathogens
Grégory Jubelin, Carolina Varela Chavez, Frédéric Taieb, Mark J. Banfield, Ascel Samba-Louaka, Rika Nobe, Jean-Philippe Nougayrède, Robert Zumbihl, Alain Givaudan, Jean-Michel Escoubas, Eric Oswald
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0004855
Abstract: The cycle inhibiting factor (Cif) produced by enteropathogenic and enterohemorrhagic Escherichia coli was the first cyclomodulin to be identified that is injected into host cells via the type III secretion machinery. Cif provokes cytopathic effects characterized by G1 and G2 cell cycle arrests, accumulation of the cyclin-dependent kinase inhibitors (CKIs) p21waf1/cip1 and p27kip1 and formation of actin stress fibres. The X-ray crystal structure of Cif revealed it to be a divergent member of a superfamily of enzymes including cysteine proteases and acetyltransferases that share a conserved catalytic triad. Here we report the discovery and characterization of four Cif homologs encoded by different pathogenic or symbiotic bacteria isolated from vertebrates or invertebrates. Cif homologs from the enterobacteria Yersinia pseudotuberculosis, Photorhabdus luminescens, Photorhabdus asymbiotica and the β-proteobacterium Burkholderia pseudomallei all induce cytopathic effects identical to those observed with Cif from pathogenic E. coli. Although these Cif homologs are remarkably divergent in primary sequence, the catalytic triad is strictly conserved and was shown to be crucial for cell cycle arrest, cytoskeleton reorganization and CKIs accumulation. These results reveal that Cif proteins form a growing family of cyclomodulins in bacteria that interact with very distinct hosts including insects, nematodes and humans.
Units of plasticity in bacterial genomes: new insight from the comparative genomics of two bacteria interacting with invertebrates, Photorhabdus and Xenorhabdus
Jean-Claude Ogier, Alexandra Calteau, Steve Forst, Heidi Goodrich-Blair, David Roche, Zoé Rouy, Garret Suen, Robert Zumbihl, Alain Givaudan, Patrick Tailliez, Claudine Médigue, Sophie Gaudriault
BMC Genomics , 2010, DOI: 10.1186/1471-2164-11-568
Abstract: RGPs account for about 60% of the genome in each of the four genomes studied. We classified RGPs into genomic islands (GIs), prophages and two new classes of RGP without the features of classical mobile genetic elements (MGEs) but harboring genes encoding enzymes catalyzing DNA recombination (RGPmob), or with no remarkable feature (RGPnone). These new classes accounted for most of the RGPs and are probably hypervariable regions, ancient MGEs with degraded mobilization machinery or non canonical MGEs for which the mobility mechanism has yet to be described. We provide evidence that not only the GIs and the prophages, but also RGPmob and RGPnone, have a mosaic structure consisting of modules. A module is a block of genes, 0.5 to 60 kb in length, displaying a conserved genomic organization among the different Enterobacteriaceae. Modules are functional units involved in host/environment interactions (22-31%), metabolism (22-27%), intracellular or intercellular DNA mobility (13-30%), drug resistance (4-5%) and antibiotic synthesis (3-6%). Finally, in silico comparisons and PCR multiplex analysis indicated that these modules served as plasticity units within the bacterial genome during genome speciation and as deletion units in clonal variants of Photorhabdus.This led us to consider the modules, rather than the entire RGP, as the true unit of plasticity in bacterial genomes, during both short-term and long-term genome evolution.The portion of the bacterial genome common to all strains in a defined set of species and required for basic cellular functions is known as the core genome. The genes variably present between individual strains constitute the flexible genome [1-3]. The estimate of the core and the flexible genomes not only depend on the phylogenetic depth of the group considered, the number of genomes available for comparison but also on the methodology used [3]. Some genes of the flexible genome may play a role in adaptation to special growth conditions, such as t
Carnot Factor of a Vapour Power Cycle with Regenerative Extraction  [PDF]
Duparquet Alain
Journal of Modern Physics (JMP) , 2017, DOI: 10.4236/jmp.2017.811107
Abstract: The present paper describes the energy analysis of a regenerative vapour power system. The regenerative steam turbines based on the Rankine cycle and comprised of vapour extractions have been used industrially since the beginning of the 20th century, particularly regarding the processes of electrical production. After having performed worked in the first stages of the turbine, part of the vapour is directed toward a regenerative exchanger and heats feedwater coming from the condenser. This process is known as regeneration, and the heat exchanger where the heat is transferred from steam is called a regenerator (or a feedwater heater). The profit in the output brought by regenerative rakings is primarily enabled by the lack of exchange of the tapped vapour reheating water with the low-temperature reservoir. The economic optimum is often fixed at seven extractions. One knows the Carnot relation, which is the best possible theoretical yield of a dual-temperature cycle; in a Carnot cycle, one makes the assumption that both compressions and expansions are isentropic. This article studies an ideal theoretical machine comprised of vapour extractions in which each cycle partial of tapped vapour obeys these same compressions and isentropic expansions.
Essay on Playfulness and Play in Children’s Art Class: A Reflection Based on Winnicott  [PDF]
Alain Savoie
Creative Education (CE) , 2019, DOI: 10.4236/ce.2019.102024
Abstract: From a survey of literature, this article presents some reflections about the value of play and playfulness as, respectively, an activity and a creative attitude of mind to be fostered in art education in children. Indeed, at the heart of any artistic creative impulse sits a playful attitude of the artist towards realitya feature that has been highlighted by the psychoanalyst Winnicott. Following his line of thought, we propose that the art teacher must place the learner in a position of being able to play with her/him, in order to overlap their two areas of playing and establish a learning space. Playfulness and play tend to be confused with impulsive and disruptive behaviours and generally more tolerated at home then school. We claim that artistic activities in school should always be play-based and take place in a playful environment because art and creation emerge from and grow in and as play.
<>: Programa breve de sensibilización sobre violencia en el noviazgo
Pick, Susan;Leenen, Iwin;Givaudan, Martha;Prado, Andrea;
Salud mental , 2010,
Abstract: introduction dating violence, a recent topic in scientific investigation, has an incidence ranging from 22% to 33% among young people. these findings are supported by a previous study that showed that about one third of high school and college students have experienced physical violence from a dating partner. similarly, national and international studies (e.g. national survey on family relations dynamics and the international dating violence study) found an incidence of violence between dating partners ranging from 10% to 45% among college students worldwide. although there is evidence that men also experience violence perpetrated by women and that violence occurs in same sex relationships, the research continues to show that violence is usually perpetrated by men against women. however, past studies have focused on the occurrence of physical violence which signals the possibility that other types of violence, such as emotional or social, have a higher incidence. their incidence varies and the harmful physical, emotional, and social consequences that they imply point to the need of creating prevention programs targeted at youth populations. it is important to prevent violence in a first stage by raising youth's awareness of this problem and, ideally, also by achieving a change in their behaviors and attitudes as well as in the social norms that promote its occurrence. in order to address all of these components of prevention, programs have been developed that do not only inform youth about violence, but also facilitate the formation of social skills through active participation and role playing which allows individuals to practice new models of interaction that are violence free. in addition, programs have to consider that many schools lack the disposition or the resources to impart long prevention workshops. for this reason, the development of brief prevention strategies has become imperative. the program ?i want to, i can… prevent violence: raising awareness of da
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