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1
Xu, Chuanbin. "The stability and cytotoxic properties of xenorxides and xenorhabdins, secondary metabolites of the entomopathogenic nematode symbiont, Xenorhabdus bovienii, Enterobacteriaceae". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37671.pdf.
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Sirs, Heidi Louise. "Molecular and biological studies on nematicidal strains of Xenorhabdus species". Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409877.
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Baxter, Laura April. "The identification and characterisation of insecticidal toxins from Xenorhabdus species". Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411586.
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Pinyon, Rebecca A. "Isolation and characterisation of novel non-ribosomal peptide synthetase genes from the entomopathogenic Xenorhabdus bovienii T228". Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09php659.pdf.
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Cambon, Marine. "Heterogeneity within infections : the case of the vector-borne insect pathogen, Xenorhabdus nematophila". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30308.
Testo completoAbstract (sommario):
De nombreuses études ont jusqu'ici considéré les infections comme étant des interactions deux-à-deux, entre un hôte et un pathogène, minimisant ainsi la complexité du processus infectieux. En effet, les infections sont souvent très hétérogènes, menant à des interactions plus complexes. Au cours de ce travail, nous cherchons à répondre à deux questions: (i) La transmission d'un pathogène peut-elle être impactée lorsque de l'hétérogénéité phénotypique apparaît dans sa population au cours de l'infection ? (ii) Comment les pathogènes interagissent-ils avec la communauté bactérienne généralement associée à l'hôte avant l'infection ? Pour étudier ces questions, nous nous sommes intéressés à Xenorhabdus nematophila, une bactérie pathogène d'insectes transmise par un vecteur, le némaotde Steinernema carpocapsae. Au cours d'une infection par X. nematophila, différentes sous-populations ayant différentes caractéristiques phénotypiques sont produites. Nous avons cherché à déterminer les mécanismes moléculaires responsables de cette diversification phénotypique, ainsi que sa potentielle valeur adaptative pour X. nematophila. Nous avons montré que certaines de ces formes phénotypique sont des mutants qui semblent être sous forte sélection positive au cours de l'infection. À l'inverse, ces mutants ont un impact négatif sur la reproduction du vecteur nématode, ce qui réduit leur transmission. La dynamique d'hétérogénéité phénotypique chez X. nematophila semble donc déterminée par des pressions de sélections contraires à court terme et à long terme. La production de molécules anti-microbiennes chez X. nematophila devraient lui permettre de dominer la communauté bactérienne à l'intérieur de l'insecte et faciliter sa ré-association avec son vecteur. Nous avons donc décrit la composition de la communauté microbienne présente dans des insectes morts d'une infection par X. nematophila, et montré qu'en dépit de sa production d'antibiotiques, X. nematophila est loin de dominer la communauté microbienne après la mort de l'insecte. Elle cohabite avec des bactéries provenant à la fois du microbiote de l'hôte insecte, et de celui du vecteur nématode. Cela soulève de nombreuses questions sur le rôle d'autres microorganismes dans les interactions Xenorhabdus-Steinernema, et sur leur influence dans l'évolution de cette symbiose mututalisteNumerous studies have considered infections as pairwise interactions between a single pathogen and its host, sometimes leading to an incomplete picture of infectious processes. In this work, we focused on more complex types of interactions that arise because infections are usually heterogeneous. More precisely, we have investigated two main issues: (I) how pathogen transmission is impacted by phenotypic heterogeneity which arises within the pathogen population during the infection, and (ii) how do pathogens interact with the bacterial community which is naturally associated to the host before infection? To assess these questions, we have been studying Xenorhabdus nematophila, an insect-killing bacterial pathogen which is transmitted by a nematode vector, Steinernema carpocapsae. One interesting feature of X. nematophila is that it produces different sub-populations during the course of an infection, each one having distinctive phenotypic features (e.g. one form produces antibiotics and is mobile, while the other does not produce antibiotics nor flagella). In this work, we first tried to identify the molecular mechanisms responsible for this diversification of phenotypes, and tested if phenotypic heterogeneity in X. nematophila has some adaptive value. We showed that some of these phenotypic forms were mutants, which seem to be under strong positive selection during infection. We also showed, however, that these mutants impair nematodes reproduction, which in turn reduces transmission. Therefore, the dynamics of phenotypic heterogeneity in X. nematophila seems to be determined by contradictory short-term and long-term selective pressures. A second interesting feature of X. nematophila is that it produces a lot of antimicrobial compounds which should allow it to dominate the bacterial community inside the insect it has killed. This can be key to ensure the re-association of X. nematophila with its nematode vector inside the insect cadaver. We investigated the bacterial composition of the microbial communities present in insects cadavers after infection by X. nematophila. We found that despite the numerous antibiotics it is able to secrete, X. nematophila is far from dominating microbial community after host death. It rather cohabits with microorganisms from the microbiota of both the insect host and the nematode vector. This raises numerous questions about the impact of these other microorganisms on Xenorhabdus-Steinernema interactions, and therefore on their potential influence on how this mutualistic association has evolved
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Roder, Alexandra Catherine, e Alexandra Catherine Roder. "Influence of Xenorhabdus Symbionts on Gonad Development and Pheromone Production of First-Generation Adult Steinernema Nematodes (Nematoda: Steinernematidae)". Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/626344.
Testo completoAbstract (sommario):
Entomopathogenic Steinernema nematodes (Nematoda: Steinernematidae) have a mutualistic relationship with Xenorhabdus bacteria (Gamma-Proteobacteria Enterobacteriaceae). The two partners form an insecticidal alliance that is successful in killing a wide range of insects. A few studies have shown that Steinernema IJs have an enhanced virulence and reproductive fitness when they associate with their cognate symbionts. However, there are unanswered questions regarding the physiological interactions that govern and perpetuate the interactions between different nematode developmental stages and their bacterial partners. In this study, we evaluated gonad development and maturation time of first-generation adults of S. carpocapsae and S. feltiae adults when reared under four bacterial scenarios: a) cognate symbiotic, b) non-cognate symbiotic bacterial strain, c) non-cognate symbiotic bacterial species and d) non-symbiotic bacteria (Serratia proteamaculans). For comparative purposes, we also considered adult nematodes reared in vivo in Galleria mellonella larvae to assess nematode development under natural conditions. Furthermore, in this study we also measured production of nematode pheromones (ascarosides), which play a key role in mating and reproduction. For this purpose, we considered in vitro rearing methods (with cognate and non-cognate Xenorhabdus symbionts) to qualitatively and quantitatively characterize ascarosides produced by first-generation adults. Our data showed that for both Steinernema spp. tested, time to adult maturation and gonad development was tightly dependent on the bacterial conditions under which juveniles were reared. However, contrasting results were observed when assessing total body length and gonad size. S. feltiae males and females size (body length and width) and respective gonad length were smaller when reared with a non-cognate symbiotic species. Additionally, non-symbiotic bacteria did not sustain S. feltiae maturation to adult stages. Contrarily, S. carpocapsae juveniles developed to adults when reared with any of the bacterial conditions tested, including with non-symbiotic Serratia proteamaculans. Additionally, S. carpocapsae adults, unlike S. feltiae, did not exhibit enhanced body and gonad size when reared with their cognate symbiont. In fact, S. carpocapsae males and females had larger gonad lengths when reared with a non-cognate symbiotic strain, XnAna (X. nematophila associated with S. anatoliense). S. carpocapsae males and females had significantly underdeveloped gonads when reared with non-symbiotic bacteria. In both Steinernema spp., sex ratio was not impacted by the bacterial condition. However, sex ratio (female:male) S. carpocapsae, decreased from 2:1 to 1:1 when reared with non-symbiotic bacteria. The body and gonad sizes of Steinernema spp. reared in vitro with their cognate symbiont were significantly smaller than those grown in vivo. Ascaroside production in either Steinernema spp. was not significantly impacted by the rearing conditions. In S. carpocapsae, a significant increase in glucoside-1 was observed when the nematodes were reared with cognate or non-cognate bacteria. No detectable quantities of asc-C11 were produced by S. feltiae nematodes when reared with a non-cognate symbiotic bacterial species. We conclude that bacterial symbionts influenced maturation and development of first-generation adults’ in both Steinernema spp. tested in this study. However, response to the bacterial symbionts was species specific. Additionally, this study showed that Xenorhabdus as a food source plays an important role in the type and amount of ascarosides produced by Steinernema spp.
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Sartori, Thaís. "Avaliação da atividade leishmanicida de metabólicos de bactérias entomopatogênicas". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/131895.
Testo completoAbstract (sommario):
A leishmaniose, doença parasitária vetoriada causada por protozoários do gênero Leishmania, é uma das principais doenças tropicais negligenciadas do mundo. Os medicamentos atualmente disponíveis para o tratamento das leishmanioses são insatisfatórios, principalmente devido à baixa efetividade dos mesmos, surgimento de resistência do parasito ou reações adversas graves apresentadas pelos pacientes. Nas últimas décadas, tem havido um interesse renovado em produtos naturais derivados de micro-organismos como fonte para a concepção de novas drogas. As bactérias entomopatogênicas Xenorhabdus nematophila e Photorhabdus luminescens produzem grande número de metabólitos secundários, muitos deles têm efeitos tóxicos específicos sobre as células eucarióticas. O objetivo deste trabalho foi avaliar a atividade leishmanicida de sobrenadantes de culturas destas bactérias. Os testes in vitro foram realizados sobre formas promastigotas e amastigotas de Leishmania amazonensis e incluíram o efeito citotóxico dos sobrenadantes sobre macrófagos. Ambos os sobrenadantes de culturas de P. luminescens e X. nematophila mostraram atividade leishmanicida significativa contra as formas promastigotas de L. amazonensis (valores de CI50 de 7,5 % e 0,63 % (v/v), respectivamente). O sobrenadante de cultura de X. nematophila foi o mais efetivo e o mais estável ao calor. Além disso, ambos os sobrenadantes de culturas continham pequenas moléculas que estimularam a atividade leishmanicida de macrófagos por um mecanismo independente de óxido nítrico. Estes resultados revelaram que estas bactérias entomopatogênicas são fontes potenciais para a concepção de novos medicamentos contra a leishmaniose.Leishmaniasis, a vector-borne parasitic disease caused by protozoa of the genus Leishmania, is one of the main neglected tropical diseases in the world. The drugs currently available for the treatment are unsatisfactory, mainly due to their low effectiveness, parasite resistance emergence or serious adverse reactions presented by the patients. In recent decades, there has been a renewed interest in natural products derived from microorganisms as a source for the design of new drugs. The Entomopathogenic bacteria Xenorhabdus nematophila and Photorhabdus luminescens produce a large number of secondary metabolites, many of them have specific toxic effects on eukaryotic cells. The objective of this study was to evaluate the leishmanicidal activity of these bacteria culture supernatants. In vitro tests were performed on promastigote and amastigote forms of L. amazonensis and included the cytotoxic effect of the supernatants on macrophages. Both supernatants from P. luminescens and X. nematophila cultures showed significant leishmanicidal activity against promastigotes forms of L. amazonensis (IC50 values of 7.5% and 0.63 % (v/v), respectively). The supernatant from X. nematophila was the most effective and more heat-stable. Furthermore, both culture supernatants contained small molecules that stimulated the leishmanicidal activity of macrophages by a mechanism independent of nitric oxide. These results revealed that these entomopathogenic bacteria are potential sources for the development of new drugs against leishmaniasis.
8
He, Hongjun. "Thermal adaptation in Xenorhabdus spp., bacterial symbionts of entomopathogenic nematodes, Steinernema spp". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0014/MQ42392.pdf.
Testo completo
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Lee, Ming-Min. "A Phylogenetic Hypothesis on the Evolution and Interactions of Xenorhabdus Spp. (Gamma-Proteobacteria) and Their Steinernema Hosts (Nematoda: Steinernematidae)". Thesis, The University of Arizona, 2009. http://hdl.handle.net/10150/193414.
Testo completoAbstract (sommario):
Nematodes in the genus Steinernema (Nematoda: Steinernematidae) and their associated bacteria Xenorhabdus spp. (Gamma-Proteobacteria) are an emergent model of terrestrial animal-microbe symbiosis. Although interest in this association initially arose out of their potential as biocontrol agents against insect pests (Tanada and Kaya, 1993), this mutualistic partnership is currently viewed more broadly under the umbrella of basic sciences to inform ecology, evolution, biochemistry, molecular, among other disciplines (Burnell and Stock, 2000; Forst and Clarke, 2002).Despite advances in the discovery and field application of this nematode-bacterium partnership, and the growing popularity of this model system, relatively little has been published to uncover the evolutionary facets of their association. This study adds to the body of knowledge regarding nematode-bacteria symbiosis by 1) producing novel, multi-gene phylogenies for Steinernema and Xenorhabdus; 2) proposing a possible scenario for historical association in the form of a cophylogenetic hypothesis; 3) describing a newly discovered Steinernema species from France.
10
Hu, Kaiji. "Nematicidal properties of Xenorhabdus spp. and Photorhabdus spp., bacterial symbionts of entomopathogenic nematodes". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0013/NQ52710.pdf.
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An, Ruisheng. "Gene expression in moraxella osloensis, photorhabdus temperata and xenorhabdus koppenhoeferi during host infection". The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1180533739.
Testo completo
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Bisch, Gaëlle. "Les bactéries entomopathogènes du genre Xenorhabdus : description pathologique et génomique de souches à la virulence atténuée". Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20050/document.
Testo completoAbstract (sommario):
Les entérobactéries du genre Xenorhabdus sont pathogènes de larves d'insectes et symbiotiques de nématodes du genre Steinernema. En lutte biologique, les couples Steinernema-Xenorhabdus sont utilisés contre un large spectre d'insectes ravageurs de culture. Les deux partenaires du couple modèle Steinernema carpocapsae-Xenorhabdus nematophila peuvent être expérimentalement dissociés tout en restant pathogènes pour les insectes. En revanche, certaines souches de Xenorhabdus sont non-virulentes lorsqu'elles sont injectées directement dans une larve d'insecte. L'objectif de cette thèse est de caractériser deux souches non-virulentes de Xenorhabdus, X. poinarii G6 (Xp G6) et X. bovienii CS03 (Xb CS03). Les souches appartenant à l'espèce non-virulente X. poinarii possèdent des génomes de petite taille. Nous avons mis en évidence un phénomène de réduction génomique due à la délétion de larges régions génomiques chez la souche Xp G6. Cette évolution pourrait avoir eu lieu suite à un transfert des fonctions bactériennes de virulence à son nématode hôte et/ou à sa spécialisation envers certains coléoptères. Au sein de l'espèce X. bovienii, Xb CS03 est non-virulente par injection dans les lépidoptères Spodoptera littoralis et Galleria mellonella. Par rapport à d'autres couples némato-bactériens Steinernema sp.-X. bovienii, le couple formé par Xb CS03 et son nématode symbiotique S. weiseri 583 présente également une virulence atténuée sur ces lépidoptères. Le génome de Xb CS03 est de très grande taille et contient un grand nombre de gènes dégradés (pseudogènes). Une comparaison génomique entre Xb CS03 et une souche virulente appartenant à la même espèce, X. bovienii SS-2004 (Xb SS-2004), montre que Xb CS03 est plus riche que Xb SS-2004 en gènes codant des chaînes d'assemblage enzymatiques NRPS/PKS (non-ribosomal peptide synthase/polyketide synthethase) produisant des métabolites antimicrobiens potentiels. A l'inverse, Xb SS-2004 contient davantage de gènes codant des facteurs de virulence de type hémolysine, adhésine ou systèmes de sécrétion. Ceci suggère deux scénarios évolutifs différents, privilégiant une forte virulence pour Xb SS-2004 et l'élimination des compétiteurs au sein du cadavre de l'insecte pour Xb CS03. Enfin, une recherche de facteurs de virulence potentiels a été effectuée par une approche de génomique comparative entre les souches non-virulentes Xp G6 et Xb CS03, d'une part et trois souches de Xenorhabdus virulentes, d'autre part. L'analyse fonctionnelle de gènes candidats a été entamée. En conclusion, la caractérisation de nouveaux modèles bactériens dans le genre Xenorhabdus ouvre le champ à l'identification de nouvelles stratégies de virulence et de nouveaux facteurs de virulence chez les bactéries entomopathogènesXenorhabdus are enterobacteria pathogenic of insect larvae and symbiotic of nematodes from the Steinernema genus. The Steinernema-Xenorhabdus associations are used against a wide range of insect pests. The two partners of the model Steinernema carpocapsae-Xenorhabdus nematophila association can be experimentally dissociated. Each partner is pathogenic for insect larvae. Contrarily, some other Xenorhabdus strains are non-virulent when injected directly into insect larvae. In this thesis, we characterized two non-virulent Xenorhabdus strains, X. poinarii G6 (Xp G6) and X. bovienii CS03 (Xb CS03). Strains from the X. poinarii species had small-sized genomes. We showed that the Xp G6 strain had undergone a genome reduction due to the deletion of large genomic regions. Transfer of virulence functions from the bacteria to the nematode and/or the specialization of the association towards coleopteran insects are likely the cause of this evolution. Within the X. bovienii species, Xb CS03 was non-virulent strain when injected into the Spodoptera littoralis and Galleria mellonella lepidopteran insects. When compared to other Steinernema-X. bovienii pairs, the association between Xb CS03 and its symbiotic nematode S. weiseri 583 had also a lower virulence on those insects. Xb CS03 had a large-sized genome and harbored numerous degraded genes (pseudogenes). Genome comparison between Xb CS03 and a virulent strain from the same species, X. bovienii SS-2004 (Xb SS-2004), showed that Xb CS03 contained more loci encoding NRPS/PKS enzymes (non-ribosomal peptide synthase/polyketide synthethase), producing potential antimicrobial metabolites, than Xb SS-2004. On the other hand, Xb SS-2004 contained more genes encoding virulence factors such as hemolysins, adhesins or secretion systems. This suggests that the two strains followed different evolutionary scenarios, favoring strong virulence in Xb SS-2204 and elimination of competitors for Xb CS03.Finally, we searched for potential virulence factors by comparing the genomes of the non-virulent strains Xp G6 and Xb CS03 with three virulent strains. Functional analyses of the candidates are in progress. In conclusion, characterizing new bacterial models in the Xenorhabdus genus paves the way for the identification of new virulence strategies and new virulence genes in entomopathogenic bacteria
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Isaacson, Peter J. "Antimicrobial activity of Xenorhabdus sp. (Enterobacteriaceae), symbiont of the entomopathogenic nematode, Steinernema riobrave (Rhabditida: Steinernematidae)". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0027/MQ51364.pdf.
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Sicard, Mathieu. "Modalités écologiques et évolutives des interactions entre les nématodes entomopathogènes Steinernema et leurs symbiotes bactériens Xenorhabdus". Montpellier 2, 2003. http://www.theses.fr/2003MON20193.
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Vigneux, Fabienne. "Interaction hôte-pathogène : apoptose induite par une nouvelle cytotoxine secrétée par la bactérie entomopathogène "xenorhabdus nematophila"". Montpellier 2, 2005. http://www.theses.fr/2005MON20173.
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Vo, Tien Duy [Verfasser], Helge Björn [Gutachter] Bode e Eugen [Gutachter] Proschak. "Target identification of peptides from Xenorhabdus and Photorhabdus / Tien Duy Vo ; Gutachter: Helge Björn Bode, Eugen Proschak". Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2021. http://d-nb.info/1225793173/34.
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Tabil, Magnus Amos. "Studies on the use of Xenorhabdus spp. for the management of root-knot nematode (Meloidogyne javanica) on tomato". Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487485.
Testo completoAbstract (sommario):
The effect of cells and toxins of Xenorhabdus spp. as biological .control on root-knot nematode (Meloidogyne javanica) was investigated. The mutualist b~cteria were obtained from two entomopathogenic nematodes, Steinemema abbasi and S. riobrave originating from the United Arab Emirates and were identified to the genus level using molecular techniques and the partial 16S rRNA gene sequences were deposited with the GENBANK. The bacteria were given Accession numbers as 00186672 for Xenorhabdus sp. RUAE (fro':l Steinemema abbasl) and 00186671, 00186674 and 00186673 for Xenorhabdus sp. 119, Xenorhabdus sp.120 and Xenorhabdus sp.124 from and S. riobrave. 00186672 was closely related to X. japonica and X. nematophila while the other three were found to be same species having 100% gene sequence homology. Cells and toxins of X. bovienii, X. nematophila and Xenorhabdus sp. RUAE (00186672) proved nematoxic to M. javanica. Higher concentrations of cells and toxins were more effective in immobilisation of juveniles and suppression of hatching of eggs than the lower concentrations. At 25°C, X. nematophila inhibited more egg hatch than ?. bovienii. The four newly isolated Xenorhabdus spp. equally inhibited egg' hatch and immobilised J2. At concentration of 2x1 07 cells/ml, X. nematophila, Xenorhabdus sp. 119 (00186671) and Xenorhabdus sp.120 (00186674) completely prevented egg hatch. Cell suspensions of all the Xenorhabdus spp. used caused more than 80-90% immobilisation of juveniles. On phytotoxicity, 30min exposure of roots of tomato seedlings recorded the highest survival at concentrations of 2x107 and 4x107cells/ml. X. nematophila and Xenorhabdus sp. RUAE (00186672) when stored in compost soil for 2 months caused over 60% mortality of larvae of Gallaria mellonella. When the same bacteria were stored in sealed bottles either in a fridge (at 5°C) or on the laboratory bench for one year recorded over 60% immobilisation of juveniles of M. incognita. When used as a soil drench, all the bacteria reduced penetration of roots and production of eggs. Similar results were obtained when tomato plants were treated with bacteria as bare-root dip for 30 min. When the bacteria were applied as bare-root dip for the tomato seedlings and transplanted into soil naturally-infested with root-knot nematode, the suppression of penetration and egg formation was less effective.
18
Huot, Louise. "Analyse moléculaire de la réponse immunitaire du lépidoptère Spodoptera frugiperda au complexe nématobactérien entomopathogène Steinernema carpocapsae-Xenorhabdus nematophila". Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTG084.
Testo completoAbstract (sommario):
Les complexes nématobactériens (CNBs) entomopathogènes sont des associations naturelles symbiotiques et mutualistes entre des nématodes et des bactéries parasites d’insectes. Dans le cadre de ces associations, le nématode sert tout d’abord de vecteur à la bactérie, qu’il transporte dans le sol et libère à l’intérieur du corps des insectes. La bactérie augmente quant à elle la virulence du CNB, puis sert de ressource nutritive au nématode dans le cadavre de l’insecte. En raison de l’originalité de ces pathogènes et de leur potentiel en lutte biologique contre les insectes ravageurs de cultures, les modalités de leurs interactions avec les insectes ont fait l’objet de nombreuses études. Ces travaux ont permis d’établir que la capacité d’un CNB à infecter et à tuer un hôte dépend d’une combinaison de facteurs écologiques et comportementaux, ainsi que du dialogue s’établissant entre chaque membre du CNB et le système immunitaire de l’insecte. Les insectes possèdent un système immunitaire élaboré et capable de répondre de façon adaptée à une grande diversité d’agents infectieux. Ce système est basé sur trois composantes principales : des barrières épithéliales, des réponses cellulaires et humorales locales et des réponses humorales systémiques. Bien qu’un grand nombre de stratégies et de facteurs permettant aux nématodes et aux bactéries de contrer ces trois composantes ait été identifié au sein de différents modèles d’interaction CNB-insecte, l’étude du dialogue s’établissant entre chaque partenaire et le système immunitaire des hôtes souffre d’un déficit de connaissance des aspects signalétiques et moléculaires des réponses immunitaires que les insectes opposent à ces infections duales.L’objectif premier de cette thèse était de contribuer au développement de ces connaissances au travers d’une analyse transcriptionnelle détaillée et structurée des réponses immunitaires d’un modèle d’insecte lépidoptère, Spodoptera frugiperda, à l’un des CNBs les plus étudiés, l’association S. carpocapsae-X. nematophila. Dans le contexte scientifique actuel, ce travail était tout d’abord caractérisé par deux nouveautés méthodologiques : l’utilisation d’une approche transcriptomique sur tissus immuno-compétents pour identifier les gènes de l’immunité affectés par l’infection par le CNB, et l’utilisation d’une méthode d’infection par injection de la bactérie et du nématode pour discriminer les réponses immunitaires induites par chaque partenaire. Ce travail a permis d’obtenir une image très résolutive et structurée des réponses immunitaires de l’insecte qui servira de base de travail pour (i) la caractérisation fonctionnelle des interactions des gènes de l’immunité identifiés avec chaque partenaire du CNB et (ii) l’étude détaillée du dialogue moléculaire entre le système immunitaire de S. frugiperda et le CNB. Ce travail a également été marqué par la découverte de deux potentiels nouveaux clusters de gènes immunitaires, les GBHs et les UNKs, qui sont parmi les gènes les plus fortement induits lors de l’interaction tripartite. Nos analyses bioinformatiques et tests d’activité préliminaires suggèrent que les GBHs pourraient avoir été acquis par tranfert horizontal de gènes bactériens et que les UNKs pourraient résulter d’une co-évolution d’insectes de la famille des noctuelles avec des CNBs Steinernema-Xenorhabdus. Cette hypothèse ouvre de nouvelles pistes de recherches pour la compréhension des variations de sensibilité aux CNBs entomopathogènes au sein de la diversité des insectesEntomopathogenic nematobacterial complexes (NBCs) are natural symbiotic associations between nematodes and bacteria that are pathogenic for insects. In these associations, the bacterial partner uses the nematode as a vector, which transports it in the soil and releases it inside the insect’s body. The bacterium then increases the NBC’s virulence and is used as a food supply by the nematode partner in the insect’s dead body. Due to the originality of these dual pathogens and to their potential for biological control of insect crop pests, studies have been conducted on diverse aspects of their interactions with insects. These works have shown the ability of an NBC to infect and kill an insect depends on a combination of ecological and behavioral factors, as well as on the dialogue between the two partners of the NBC and the insect’s immune system. Insects possess an elaborate immune system which is able the respond by adapted ways to a huge diversity of infectious agents. This system relies on three main components: epithelial barriers, local cellular and humoral responses and systemic humoral responses. A large number of strategies and factors used by NBCs to counteract these three components have already been identified in several NBC-insect interaction models. However, the study of the dialogue between each NBC partner and the hosts’ immune systems is currently suffering from a lack of knowledge of the signaling and molecular aspects of the insects’ immune responses to these dual infections.The first goal of this thesis was to increase this knowledge through a detailed and structured transcriptional analysis of the immune responses of a lepidopteran model, Spodoptera frugiperda, to one of the most studied NBCs, the S. carpocapsae-X. nematophila association. In the current scientific context, this work was mainly characterized by two methodologic novelties: the use of a topologic approach for the transcriptomic analysis of the induced immune responses to the infection by the NBC, and the use of an infection by injection method for the discrimination between the nematode- and the bacterium-induced immune responses. This work allowed the observation of a structured and highly resolutive picture of the induced immune responses, which will be used as a working base for (i) the functional characterization of the interactions of identified immune genes with each partner of the NBC, and (ii) for the detailed analysis of the molecular dialogue between the immune system of S. frugiperda and the NBC. Finally, this work also allowed the identification of two potential new clusters of immune genes, the GBHs and the UNKs, which are among the most overexpressed genes during the tripartite interaction. Our preliminary bioinformatics analyses and activity tests suggest the GBHs could have been acquired by horizontal gene transfer from bacteria and the UNKs could result from a coevolution between noctuids and some Steinernema-Xenorhabdus NBCs. This hypothesis opens new research trails for the understanding of the NBC-sensitivity variations within insect diversity
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Lee, Sarah Caroline. "Characterisation of the insecticidal protein toxin complex from Xenorhabdus nematophila PMF1296 : structural and biophysical analysis of the XptA1 component". Thesis, Coventry University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420164.
Testo completo
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Zhao, Lei [Verfasser], Helge Björn [Akademischer Betreuer] Bode, Helge Björn [Gutachter] Bode e Martin [Gutachter] Grininger. "Nonribosomal peptides produced by xenorhabdus and photorhabdus / Lei Zhao ; Gutachter: Helge Björn Bode, Martin Grininger ; Betreuer: Helge Björn Bode". Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2020. http://d-nb.info/1219574201/34.
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Maxwell, Philip W. (Philip William). "The interaction of surface components of Xenorhabdus nematophilus (Enterobacteriaceae) with the hemolymph of nonimmune larvae of the greater wax moth, Galleria mellonella (Lepidoptera; Galleridae)". Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23285.
Testo completoAbstract (sommario):
The following studies were done to identify factors that influence the virulence of Xenorhabdus nematophilus and the interactions of the bacterium with the nonself defence systems of nonimmune Galleria mellonella. Isolates of X. nematophilus that are qualitatively similar in biochemical properties differed significantly in virulence for G. mellonella larvae. The production of enzymes such as proteases could not account for differences in the virulence of the isolates.Growth conditions, influenced the growth rate and the interactions of the bacterium with nonimmune G. mellonella larvae. In general, X. nematophilus cells grown under aerobic conditions were more susceptible to the nonself defences of G. mellonella larvae than those grown under less than ideal conditions, resulting in increased clearance of the bacteria from the hemolymph (blood) of the insects. Clearance of the bacteria from the hemolymph of the insect was positively correlated with culture condition, culture age, and attachment to insect hemocytes in vitro.
Isolates of X. nematophilus produced flagella and fimbriae when grown under microaerobic and aerobic conditions. The type of fimbriae produced was influenced by culture conditions. The injection of both flagella and fimbriae in picogram quantities into nonimmune G. mellonella caused an increase in total hemocyte counts within these insect larvae. The injection of fimbrial and flagellar antigens into G. mellonella larvae caused changes in the hemocyte types found in circulation in the insect's hemolymph. (Abstract shortened by UMI.)
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Antonello, Ana Maria. "Efeito imunomodulador e antiparasitário de metabólitos secundários de Photorhabdus luminescens e Xenorhabdus nematophila sobre Leishmania amazonensis e Trypanosoma cruzi, in vitro". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/174986.
Testo completoAbstract (sommario):
Os fármacos atualmente disponíveis para o tratamento da Doença de Chagas e leishmaniose possuem eficácia insatisfatória, principalmente devido à resistência parasitária e reações adversas severas. Duas entomobactérias, Photorhabdus luminescens e Xenorhabdus nematophila, produzem uma variedade de metabólicos secundários tóxicos a células eucarióticas. Diante disto, testou-se a toxicidade de metabólitos secretados por P. luminescens e X. nematophila sobre Leishmania amazonensis e Trypanosoma cruzi, in vitro. Os meios condicionados de ambas bactérias mostraram significativo efeito parasiticida de forma concentração e tempo-dependente (L. amazonensis: IC50 P. luminescens = 21,80 μg/mL e X. nematophila = 0,33 mg/mL; T. cruzi: IC50 P. luminescens = 1,0 mg/mL e IC50 X. nematophila = 0,34 mg/mL) e apresentaram alta seletividade ao parasito (L. amazonensis: SIP. luminescens = 3.92 e SIX. nematophila = 19,85; T. cruzi: SIP. luminescens = 7,23 e SIX. nematophila = 14.17 para promastigotas e tripomastigotas, respectivamente). Além disso, os metabolitos estimulam a atividade de macrófagos contra amastigotas por um mecanismo independente de óxido nítrico. Com relação à caracterização dos compostos antiparasitários, sugere-se que moléculas com diferentes características atuem sobre cada parasito. P. luminescens secreta uma molécula leishmanicida de natureza peptídica menor que 3 kDa e uma molécula tripanocida de natureza não proteica, resistente a aquecimento a 100 ºC. X. nematophila produz uma molécula leishmanicida de polaridade inferior à tripanocida, uma vez que a atividade antiparasitária ficou em fases diferentes na extração com metanol. O mecanismo de ação de ambas bactérias sobre promastigotas parece estar relacionado à lesão mitocondrial, uma vez que ambas levaram à despolarização da membrana mitocondrial. X. nematophila, além disso, estimula a produção de ROS pelas formas promastigotas. A seletividade pelo parasito aliada a baixa citotoxicidade tornam estas bactérias promissoras fontes de compostos com potencial terapêutico contra leishmanioses e doença de Chagas.Drugs currently available for Chagas disease and leishmaniasis have unsatisfactory efficacy, mainly due to parasitic resistance and severe adverse reactions. Two entomobacteria, Photorhabdus luminescens and Xenorhabdus nematophila, produce a variety of secondary metabolites toxic to eukaryotic cells. So, the toxicity of the metabolites secreted by Photorhabdus luminescens and Xenorhabdus nematophila were tested against Trypanosoma cruzi and Leishmania amazonensis. The mean values of both bacteria showed a significant concentration-dependent and time-dependent effect 14.17 (L. amazonensis: IC50P. luminescens = 21.80 μg / mL and IC50X. nematophila = 0.33 mg / mL, T. cruzi: IC50P. luminescens = 1,0 mg/mL and IC50X. nematophila = 0 , 34 mg / mL), and showed a high selectivity to the parasite (L. amazonensis: SIP. luminescens = 3,92 and SIX.nematophila = 19.85, T. cruzi: SIP. luminescens = 7.23 and SIX.nematophila = 14.17 for promastigotes and trypomastigotes, respectively). In addition, cultures stimulate the activity of macrophages against amastigotes by an independent mechanism of nitric oxide. Regarding the characterization of antiparasitic compounds, it is suggested that molecules with different characteristics act on each parasite. P. luminescens secretes a leishmanicidal peptide molecule lesser than 3 kDa and a trypanocidal molecule of non-protein nature, resistant to heating at 100 °C. X. nematophila produces a leishmanicidal molecule of lower polarity than trypanocidal, since antiparasitic activity was at different phases in methanol extraction. The mechanism of action of both bacteria on promastigotes seems to be related to the mitochondrial injury, since both led to the depolarization of the mitochondrial membrane. X. nematophila, furthermore, stimulates the production of ROS by the promastigote. Selectivity by the parasite coupled with low cytotoxicity makes these bacteria promising sources of compounds with therapeutic potential against leishmaniasis or Chagas' disease.
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McMullen, John George II. "Comparative Phenotypic and Genomics Approaches Provide Insight into the Tripartite Symbiosis of Xenorhabdus bovienii with Steinernema Nematode and Lepidopteran Insect Hosts". Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/596124.
Testo completoAbstract (sommario):
Nematodes are highly diverse animals capable of interacting with almost every other form of life on Earth from general trophic interactions to intimate and persistent symbiotic associations. Much of their recognition originates from their various parasitic lifestyles. From an agricultural standpoint, plant parasitic nematodes are widely known for the destruction they can cause to crop plants, such as the case of the root-knot nematode Meloidogyne incognita, or livestock animals, like the Trichinella spiralis, which infects pigs and other animals. From a human health perspective, nematodes can cause many debilitating diseases, for example Wuchereria bancrofti, which is a causative agent of lymphatic filariasis or elephantiasis. However, not all parasitic nematodes have bad implications for human health. For instance, the diverse interactions of insect parasitic nematodes can be used to our benefit. Many of these species have been considered as biological control alternatives to different insect pests that wreak havoc on human, animal, and plant health. There still remain many questions surrounding their evolution, ecology, and physiological capabilities. Many of these taxa are hard to cultivate in the lab due to their complex and intimate lifestyles. Entomopathogenic nematodes (EPNs) are of great interest in agriculture because they vector insect pathogenic bacteria, which are capable of causing death to an insect host within 48 hours post-infection. Much of the molecular underpinnings in this system still remain to be discovered, from understanding the basic ability of these two organisms to associate with one another to genetically engineering more robust and host specific pathogens for application in the field. The focus of the research presented herein is on Steinernematidae nematodes and their bacterial symbionts. Specifically, it focused on the relationship between Xenorhabdus bovienii and its Steinernema hosts. Bioassays were designed to investigate insect virulence of X. bovienii alone in two Lepidoptera insect species with known differential susceptibility to Steinernema-Xenorhabdus pairs. A comparative genomic analysis was performed to compare different Xenorhabdus bovienii strains with observed variation in insect virulence. Results from this analysis demonstrated that virulent strains possess a type VI secretion system (T6SS) locus that is completely absent in strains with attenuated virulence. Bacterial competition assays between T6SS+ and T6SS- strains suggest this locus is involved in bacterial competition. Additionally, symbiont preference assays were carried out to investigate whether Steinernema hosts are able to discern between virulent and attenuated X. bovienii strains. Results from these assays revealed that Steinernema nematodes are able to distinguish between cognate and non-cognate X. bovienii symbionts, giving preference to virulent strains over those with attenuated virulence. Altogether these results provide further evidence that supports the notion that symbiont-switching events have occurred over the Steinernema-Xenorhabdus co-evolutionary history. Specifically, the competitive virulence of certain X. bovienii strains may have conferred them the ability to be selected by different Steinernema hosts, therefore contributing to the success of the nematode-bacterium partnership in being pathogenic to diverse insect hosts.
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Nollmann, Friederike Inga [Verfasser], Helge B. [Gutachter] Bode e Martin [Gutachter] Grininger. "Characterization and synthesis of selected secondary metabolites produced by Xenorhabdus and Photorhabdus spp / Friederike Inga Nollmann ; Gutachter: Helge B. Bode, Martin Grininger". Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2017. http://d-nb.info/1127639463/34.
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Neubacher, Nick Larry Valentin [Verfasser], Helge Björn [Akademischer Betreuer] Bode, Helge Björn [Gutachter] Bode e Eckhard [Gutachter] Boles. "Regulation of specialized metabolites in Photorhabdus and Xenorhabdus / Nick Larry Valentin Neubacher ; Gutachter: Helge Björn Bode, Eckhard Boles ; Betreuer: Helge Björn Bode". Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2020. http://d-nb.info/1223538060/34.
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Brillard, Julien. "Caractérisation de cytolysines chez les bactéries entomopathogènes des genres Xenorhabdus et Photorhabdus, et étude de leur rôle dans la relation bactérie-insecte". Lyon 1, 2001. http://www.theses.fr/2001LYO10247.
Testo completoAbstract (sommario):
Les entérobactéries des genres Xenorhabdus et Photorhabdus associées symbiotiquement à des nématodes des sols sont pathogènes par injection chez de nombreux insectes. Ces bactéries produisent in vitro des hémolysines, protéines souvent impliquées dans la virulence chez d'autres bactéries pathogènes, entraînant la cytolyse d'hématies et parfois d'autres cellules. L'objectif de ce travail a été de caractériser de tels facteurs, puis d'évaluer leur rôle dans la virulence chez l'insecte. Des études in vitro ont mis en évidence la présence de deux activités cytolytiques (C1 et C2) pour les hémocytes d'insectes (cellules immunocompétentes capables de phagocytose et d'encapsulement) dans les surnageants de culture des souches de Xenorhabdus. Chez X. Nematophila F1, ces activités ciblent les deux types d'hémocytes majoritaires du lépidoptère Spodoptera littoralis, ainsi que des hématies de mammifères. Afin de caractériser le(s) gène(s) codant pour C1, le criblage d'une banque du prophage de X. Nematophila a permis de cloner un locus de 5,7 kb qui entraîne une activité hémolytique chez E. Coli. Ce locus, qui en fait induit l'activité hémolytique cryptique SheA d'E. Coli, code pour une holine fonctionnelle, protéine phagique formant des pores dans la membrane externe des bactéries. L'hypothèse de son implication dans la sécrétion de l'activité C1 est discutée. Chez P. Luminiscens, une activité cytolytique associée aux bactéries et s'exerçant sur hématies de cheval est produite in vitro. Les gènes phlA et phlB codant pour cette activité ont été identifiées dans la séquence du génome de P. Luminiscens TT01. Ces gènes présentent des similarités de séquences avec les cytolysines de la famille des SAST (Secretion and Activation Serratia Type of Hemolysin). L'activité cytolytique est induite en conditions carencées en fer, et des fusions de promoteurs avec des gènes rapporteurs ont révélé une augmentation transcriptionnelle. Par ailleurs, la transcription des gènes in vivo dans l'hémolymphe d'insecte a été vérifiée. Le mutant phlA- construit par échange allélique présente le même pouvoir pathogène que la souche sauvage. Cependant, il est moins compétitif que la souche sauvage au cours des septicémies chez l'insecte, indiquant que ce facteur de virulence ne joue pas un rôle majeur dans le pouvoir pathogène de la bactérie.
27
Reimer, Daniela [Verfasser], Helge Björn [Akademischer Betreuer] [Gutachter] Bode e Eckhard [Gutachter] Boles. "Identification and characterization of selected secondary metabolite biosynthetic pathways from Xenorhabdus nematophila / Daniela Reimer ; Gutachter: Helge Björn Bode, Eckhard Boles ; Betreuer: Helge Björn Bode". Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2014. http://d-nb.info/1143230019/34.
Testo completo
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Reimer, Daniela [Verfasser], Helge Björn [Akademischer Betreuer] Bode e Eckhard [Gutachter] Boles. "Identification and characterization of selected secondary metabolite biosynthetic pathways from Xenorhabdus nematophila / Daniela Reimer ; Gutachter: Helge Björn Bode, Eckhard Boles ; Betreuer: Helge Björn Bode". Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2014. http://nbn-resolving.de/urn:nbn:de:hebis:30:3-331798.
Testo completo
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Zhou, Qiuqin [Verfasser], Helge B. [Gutachter] Bode e Martin [Gutachter] Grininger. "Identification of selected secondary metabolites from Xenorhabdus and investigation on the biosynthesis of anthraquinones from Photorhabdus / Qiuqin Zhou. Gutachter: Helge B. Bode ; Martin Grininger". Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2016. http://d-nb.info/1112601457/34.
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30
Halwani, Adla E. "Role of apolipophorin-III in the immediate antibacterial responses of Galleria mellonella larvae (Lepidoptera:Pyralidae)". Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36602.
Testo completoAbstract (sommario):
Apolipophorin-III is a hemolymph protein known for its role in lipid transport. Apolipophorin-III isolated from the hemolymph of last instar larvae of Galleria mellonella bound to the surface of the insect pathogenic Gram-negative bacterium Xenorhabdus nematophilus and to the lipid A moiety of its lipopolysaccharide. This binding reduced the toxicity of the lipopolysaccharide to hemocytes and decreased the inhibitory effect of the lipopolysaccharide on phenoloxidase. Apolipophorin-III also bound to the Gram-positive bacterium Micrococcus lysodeikticus; this enhanced the activity of hen egg lysozyme on the organism as well as the lytic activity of G. mellonella cell-free hemolymph.The involvement of apolipophorin-III in the immune responses of G. mellonella larvae to lipoteichoic acids, surface components of Gram-positive bacteria, was examined. Lipoteichoic acids from Bacillus subtilis, Enterococcus hirae and Streptococcus pyogenes caused a dose- and time-dependent drop in the total counts of circulating hemocytes and a partial or complete depletion of plasmatocytes depending on the species of lipoteichoic acid. All lipoteichoic acids tested activated phenoloxidase in vitro; however, in vivo, only B. subtilis lipoteichoic acid elevated the phenoloxidase activity while the other two suppressed it. Binding of apolipophorin-III to lipoteichoic acids was demonstrated. Apolipophorin-III prevented the complete depletion of plasmatocytes and depressed the activation of phenoloxidase by lipoteichoic acid from B. subtilis. The concentration of apolipophorin-III in hemolymph two hours post injections of lipopolysaccharides or lipoteichoic acids into larvae of G. mellonella did not change with respect to control insects that received phosphate-buffered saline. The concentration of apolipophorin-III in hemolymph at the end of the feeding larval stage was 8--12 mg/mL of hemolymph. Apolipophorin-III was present in significant amounts in the prepupal, pupal and adult stages. The protein was detected immunologically in hemocyte lysates, plasma and fat body. Non-denaturing polyacrylamide gels and immunoblots of fresh hemolymph suggested that apolipophorin-III is associated with a 77 kDa protein.
31
Emelianoff, Vanya. "Les problèmes de couple dans les symbioses némato-bactériennes parasites d'insecte". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2008. http://tel.archives-ouvertes.fr/tel-00528291.
Testo completoAbstract (sommario):
Les nématodes entomopathogènes Steinernema sont associés symbiotiquement à des bactéries du genre Xenorhabdus. Leur cycle de vie comprend deux phases : une phase libre, dans le sol, où les nématodes portent leurs symbiotes dans le tube digestif, et une phase parasite, dans l'insecte, où les deux partenaires se multiplient côte à côte. Le bilan fin de l'interaction, globalement bénéfique pour les deux partenaires, a été peu étudié pour le moment. Dans un premier temps, nous avons abordé ces symbioses d'un point de vue coûts-bénéfices pour le nématode afin d'identifier les pressions de sélection agissant sur son investissement dans la symbiose. Nous montrons que l'association est à la fois bénéfique (reproduction en phase parasitaire) et coûteuse (mortalité en phase libre) pour le nématode, en proportion de sa charge symbiotique. Ces corrélations engendrent un compromis survie-reproduction pour le nématode, médié par ses symbiotes. Selon les conditions environnementales, elles pourraient éventuellement déstabiliser l'association, et, notamment, altérer sa spécificité. Dans un second temps, nous avons donc exploré la spécificité de ces associations dans la nature et au laboratoire. Lors d'un échantillonage de terrain, nous avons retrouvé la spécificité de ces associations largement décrite par ailleurs. Au laboratoire, la réassociation expérimentale entre nématodes et bactéries non natives montre que le spectre des bactéries retenues est plus étroit que le spectre des bactéries bénéfiques. De plus, des différences de modalités d'association apparaissent entre espèces de nématodes, qui suggèrent que la correspondance nématode - bactérie ne serait pas aussi stricte que prévu.
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Emelianoff, Vanya. "Les problèmes de couple dans les symbioses némato-bactériennes parasites d'insecte". Phd thesis, Montpellier 2, 2008. http://www.theses.fr/2008MON20054.
Testo completoAbstract (sommario):
Les nématodes entomopathogènes du genre Steinernema sont associés symbiotiquement à des bactéries du genre Xenorhabdus. Ces associations sont traditionnellement qualifiées de mutualistes car chacun des partenaires bénéficie de la présence de l'autre. Toutefois, l'originalité du cycle de vie de ces associations permet de s'interroger sur la réalité de cette réciprocité des bénéfices. En effet, le cycle de vie de ces associations comprend deux phases : une phase libre, dans le sol, où les nématodes portent leurs symbiotes dans le tube digestif, et une phase parasite, dans l'insecte, où les deux partenaires se multiplient côte à côte. La symbiose est clairement bénéfique pour le nématode en phase parasite, ce qui est moins net en phase libre ; c'est le contraire pour la bactérie. Dans un premier temps, nous avons abordé ces symbioses d'un point de vue coûts-bénéfices pour le nématode afin d'identifier les pressions de sélection agissant sur son investissement dans la symbiose. Nos résultats montrent que l'association est coûteuse pour le nématode en termes de survie en phase libre, et que ce coût augmente avec le nombre de bactéries portées. D'un autre côté, le nématode bénéficie de l'association en termes de reproduction en phase parasitaire, en proportion de sa charge symbiotique. Ces corrélations engendrent un compromis survie-reproduction pour le nématode, médié par ses symbiotes. Selon l'environnement, le bilan de l'association serait donc mitigé pour les nématodes. Ce découplage des coûts et bénéfices peut mener à des pressions de sélection contraires entre les deux phases du cycle de vie. De plus, les coûts à l'association manifestent un conflit d'intérêts entre partenaires, qui pourrait éventuellement déstabiliser l'association, et, notamment, altérer sa spécificité. Dans un second temps, nous avons donc exploré la spécificité de ces associations dans la nature et au laboratoire. Lors d'un échantillonage de terrain, nous avons retrouvé la correspondance entre une espèce de nématode et une espèce de bactérie largement décrite par ailleurs. Au laboratoire, la réassociation expérimentale entre nématodes et bactéries non natives montre que le spectre des bactéries retenues est plus étroit que le spectre des bactéries bénéfiques. De plus, des différences de modalités d'association apparaissent entre espèces de nématodes, qui suggèrent que la correspondance nématode - bactérie ne serait pas aussi stricte que prévuEntomopathogenic nematodes from Steinernema genus are symbiotically associated with Xenorhabdus bacteria. These associations are traditionally considered as mutualistic as both partners benefit from each other. However the original life cycle of these associations raises questions about their real reciprocally-beneficial status. Indeed, the symbiosis life cycle comprises two phases : a free stage in the soil, where bacteria are carried inside nematodes' gut and a parasitic stage in the insect, where both partners are separated and multiply in parallel. Benefits of the association for nematodes are clear in parasitic, but not in free stage, and it is the opposite for bacteria. We first tried to measure the balance between costs and benefits in these symbioses to identify selective pressures acting on nematode's symbiotic investment. We showed that nematodes endure costs to the association in free stage in terms of survival, these costs increasing with bacterial load. On the other side, nematodes benefit from the symbiosis in proportion of bacterial load in parasitic stage in terms of reproduction. These two antagonistic effects lead to a trade-off between nematodes' survival and reproduction which is mediated by their bacterial symbionts. Thus, depending on the environment, symbiosis has mitigated outcomes for nematodes. This decoupling of costs and benefits along the life cycle may lead to contradictory selective pressures between the two stages of the cycle. Moreover, costs of the association for nematodes indicate a conflict of interests between partners, which could challenge association stability, in particular its specificity. In a second part, we addressed the question of symbiosis specificity in natura as well as in laboratory. Field samples confirmed the already-known constancy of association between a nematode species and a bacteria species all over the world. Experimental re-associations between two nematode species and foreign bacteria showed differences between retention and benefit specificities as well as inter-specific variability. Thus the one-to-one association between nematode and bacteria species may not be as strict as previously thought
33
Noujeim, Abi Nader Elise. "Biodiversité et biogéographie des nématodes entomopathogènes au Liban : étude phylogénique et valorisation des potentiels en lutte biologique". Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20013/document.
Testo completoAbstract (sommario):
Les Nématodes Entomopathogènes (NEP) de la famille des Steinernematidae et Heterorhabditidae sont des parasites pour les insectes. Ils hébergent dans leur intestin un symbiote bactérien (genres Xenorhabdus et Photorhabdus) essentiel au succès parasitaire. Les NEP sont présents dans les sols des cinq continents de la planète. Leur diversité génétique et leurs propriétés biologiques constituent une intéressante ressource biologique. Grâce à leur entomotoxicité, les NEP sont de bons outils de lutte biologique en agriculture et en culture ornementale un peu partout dans le monde. La diversité et la biogéographie des NEP dans les cinq continents de la Terre (à l'exception de l'Antarctique) ont été étudiées partout dans le monde mais le Liban est parmi les rares pays du moyen orient où aucune prospection de ces nématodes n'a été réalisée alors que des NEP en Turquie, Syrie, Jordanie, Palestine et Egypte ont déjà été trouvés et caractérisés. L'objet de la thèse est de procéder à une étude biogéographique dans le but de connaître la diversité des NEP au Liban. L'enjeu scientifique est donc de combler un « vide » dans la connaissance de la répartition et de la biodiversité mondiale des NEP. Pour cela, un échantillonnage à l'échelle des étages de végétation est mené au Liban. Des échantillons de sol sont ainsi prélevés, mis en contact avec des larves de Galleria mellonella pour isoler les nématodes entomopathogènes et leurs symbiotes. Les nématodes et leurs symbiotes sont par la suite identifiés morphologiquement et moléculairement. Par la suite, une approche à l'échelle de l'habitat fait l'objet de cette thèse également pour étudier les interactions biotiques et abiotiques influençant la présence des nématodes entomopathogènes dans le sol. Les enjeux technologiques, exposés au second volet de la thèse, sont liés aux propriétés biologiques des nématodes et de leurs symbiotes afin de valoriser leur entomotoxicité en lutte biologique. Dans ce cadre, la sensibilité des Cephalcia tannourinensis, ravageur des cédraies au Liban, par rapport aux nématodes entomopathogènes est exploitée in vitro ; différentes espèces de nématodes entomopathogènes sont testées pour suivre leur cycle à l'intérieur des CephalciaEntomopathogenic nematodes (EPNs) are parasites of soil-dwelling insects that occur in natural and agricultural soils around the world. Thanks to their entomotoxicity, EPNs are good tools for biological control in agriculture almost everywhere in the world. They are ubiquitous, having been isolated from every inhabited continent (except Antartica) from a wide range of ecologically diverse soil habitats including cultivated fields, forests, grasslands, deserts, and even ocean beaches. Biogeographic assessments of EPNs in the Eastern Mediterranean basin have been conducted in several countries such as Turkey, Syria, Jordan, Israel, Palestine and Egypt. Lebanon is among the few countries of the Middle East for which no survey of EPNs has been done. The scientific stake is thus to fill a gap in our knowledge of EPNs distribution in the Mediterranean basin. Survey of EPNs was conducted in this framework to cover the different vegetation levels defined in Lebanon. Soil samples were removed placed in contact with Galleria mellonella to isolate entomopathogenic nematode and their symbiotic bacteria. EPNs and their bacteria were then identified morphologically and molecularly. On the other hand, despite the different national surveys conducted on EPNs distribution around the world, habitat preferences remain inadequately known for entomopathogenic nematodes. Therefore, a comprehensive understanding of their distribution and the various biotic and abiotic factors influencing their presence is also a second object of our work. Beside a technological approach related to the biological properties of the nematodes and their symbiotics: valorisation of the entomotoxicity in biological control will be part of the third shutter of the thesis. In this framework, the sensibility of cedar pests, Cephalcia tannourinensis against entomopathogenic nematodes is exploited in vitro; different EPNs species were tested to study their life cycle inside Cephalcia larvae
34
Kunkel, Brian A. "Plant Fungal Endosymbionts Alter Host-Parasite Relationships Between Generalist Herbivores (Lepidoptera: Noctuidae) and An Entomopathogenic Nematode". The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1047328087.
Testo completo
35
Orchard, Samantha S. "Oligopeptide and nucleoside salvage by the bacterium Xenorhabdus nematophila". 2005. http://catalog.hathitrust.org/api/volumes/oclc/62308491.html.
Testo completo
36
Cowles, Kimberly N. "Activity and regulation of hemolysins in the insect pathogen Xenorhabdus nematophila". 2006. http://www.library.wisc.edu/databases/connect/dissertations.html.
Testo completo
37
Hsu, KenHao, e 許耿豪. "Gene expression and characterization of the recombinant lipase from Xenorhabdus luminescens". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/18627303753282146974.
Testo completoAbstract (sommario):
碩士國立海洋大學
水產生物技術研究所
87
Xenorhabdu luminescens lipase gene encodes a 66kDa protein. The lipase gene was cloned with PCR (polymerase chain reaction) technique and overexpressed in E. coli BL21(DE3) using the pET20b(+) vector system, but the overexpressed protein formed inclusion body. Dissolving the inclusion body in 0.2% SDS can recover the lipase activity. On the other hand, the X. luminescens lipase gene expressed in BL21(DE3) using pG3K vector had basal expression of soluble lipase. Both enzymes were purified by gel electrophoresis. The optimum pH of both lipases are pH 8. The optimum temperature for SDS-lipase and soluble lipase were 40℃ and 50℃, respectively. Soluble lipase is more stable than SDS-lipase. After 1 hour incubation in 100℃ water bath, soluble lipase and SDS-lipase retained 90% and 18% activity, respectively. Fe2+ enhanced 20% activity of lipase, but Co2+, Cu2+ and Zn2+ greatly decreased the activity. SDS lipase had higher catalytic efficiency (kcat/Km) toward p-nitrophenyl butyrate. When using p-nitrophenyl caprylate and p-nitrophenyl laurate as substrates, SDS lipase had similar Km but lower kcat than soluble lipase. The enzyme was a non-specific lipase, its activity was higher than Candida rugosa lipase and Porcine pancreatic lipase by 9 and 16 fold, respectively. The enzyme deleted 10 kDa from C terminal still retained lipase activity.
38
Richards, Gregory R. "The regulator LrhA and lipase activity in Xenorhabdus nematophila insect pathogenesis". 2008. http://www.library.wisc.edu/databases/connect/dissertations.html.
Testo completo
39
Martens, Eric C. "Initiation and maintenance of Steinernema carpocapsae nematode colonization by Xenorhabdus nematophila bacteria". 2005. http://www.library.wisc.edu/databases/connect/dissertations.html.
Testo completo
40
Herbert, Tran Erin E. "Regulation of Xenorhabdus nematophila mutualism and pathogenicity by the CPXRA two-component system". 2008. http://www.library.wisc.edu/databases/connect/dissertations.html.
Testo completo
41
Pinyon, Rebecca A. "Isolation and characterisation of novel non-ribosomal peptide synthetase genes from the entomopathogenic Xenorhabdus bovienii T228 / Rebecca A. Pinyon". Thesis, 2002. http://hdl.handle.net/2440/21756.
Testo completo
42
JAKUBÍKOVÁ, Hedvika. "Vliv metabolitů entomopatogenních bakterií rodu Xenorhabdus na přežívání a reprodukci fakultativně entomoparazitických a fytofágních hlístic". Master's thesis, 2019. http://www.nusl.cz/ntk/nusl-395267.
Testo completoAbstract (sommario):
Bacteria of the genus Xenorhabdus live as the natural symbionts of the entomopathogenic nematodes of the family Steinernematidae. They produce a wide range of toxic secondary metabolites of different chemical structure and effect. The synthesis of particular products is specific for each strain of Xenorhabdus. The thesis is focused on evaluating the impact of bacterial metabolites on facultatively entomoparasitic nematodes Oscheius myriophila, the free-living nematode Caenorhabditis elegans and the phytophagous potato cyst nematode Globodera rostochiensis. Target species of nematodes were exposed to 37 strains of Xenorhabdus bacteria, isolated from various species of Steinernematidae. Testing the impact of bacterial metabolites on O. myriophila and C. elegans nematodes was performed both by direct cultivation of target species on solid medium with live bacterial cultures as well as in sterilized liquid bacteria cultures. The effect of toxic substances on G. rostochiensis was evaluated only in selected sterilized bacteria cultures.
43
Brachmann, Alexander Oliver [Verfasser]. "Isolation and identification of natural products and biosynthetic pathways from Photorhabdus and Xenorhabdus / von Alexander Oliver Brachmann". 2009. http://d-nb.info/999694499/34.
Testo completo
44
Cowles, Charles E. "Characterization of bacterial colonization factors involved in the species-specific interaction betwen Xenorhabdus nematophila bacteria and Steinernema carpocapsae nematodes". 2006. http://www.library.wisc.edu/databases/connect/dissertations.html.
Testo completo
45
Tsai, Mi-Hau, e 蔡米皓. "Identification, and analyses of metabolites and plasmids in the symbiotic bacterium, Xenorhabdus indica, of the entomopathogenic nematode, Steinernema abbasi". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/67616102827765283563.
Testo completoAbstract (sommario):
博士國立中興大學
昆蟲學系所
100
The symbiotic bacterium of the entomopathogenic nematode, Steinernema abbasi, isolated from Taiwan, was determined to be the genus Xenorhabdus based on physiological and biochemical characteristics. It was further identified to be similar to Xenorhabdus indica of S. abbasi Oman isolate as identified by the sequence analyses of its 16S rDNA. The cultured filtrates of Xenorhabdus indica from only the primary form were toxic to Sf21 and S2 cell lines, while those of both forms were not toxic to a mammalian cell line. The necrotic rates of Galleria mellonella hemocytes at 24 h after treating with the cultured filtrates of symbiotic bacteria were significantly different from those of the control, whereas the rates treated with X. indica lipopolysaccharide (LPS) were similar to those of the control. These results indicate that necrosis in G. mellonella hemocytes occurs at 24 h after treatment with the filtrates, while erythrocytes as treated with filtrates were not significantly different, revealing that the culture filtrates do not contain hemolytic substances. Inactivated bacterial cells (primary form) caused serious paralysis in G. mellonela larvae and eventually killed insects. This symptom was found to be similar to that injected with LPS extracted from the primary form. Therefore, it is suggested that LPS is neurotoxic to G. mellonella larvae. Both hemolytic rates of mammalian and insect hemocytes treated with inactivated bacteria (primary form) were capable of causing necrosis. In in vivo assays, the inactivated bacterial cells were capable of causing necrosis and subsequently killed hemocytes of both G. mellonella and Spodoptera litura larvae; however, they were comparatively lesser destructive to S. litura hemocytes. In in vitro assays, LPS from X. indica (primary form) was not markedly detrimental to G. mellonella hemocytes compared with the control groups, suggesting that LPS is not a major factor affecting insect immune system. Therefore, it is speculated that LPS and certain substances when released into insect hemocoel from symbiotic bacteria could hamper insect immune system, resulting in proliferation of symbiotic bacteria and nematodes, and subsequently causing septicemia to rapidly kill their insect hosts. Xenorhabdus indica caused ca. 95% mortality of Galleria mellonella mature larvae at 72 h after culturing, indicating that this bacterium secreted insecticidal substances in its culture medium. The cultured filtrates could also inhibit nine kinds of human pathogens and plant pathogenic fungi. The cultured filtrates screened through 10 or 100 kDa molecular sieves could inhibit the growth of Bacillus subtilis and Botrytis cinerea while those through 3-kDa sieve could inhibit B. subtilis only. However, only the filtrates through 10-kDa sieve resulted in 96.67% mortality of G. mellonella larvae at 24 h. It is thus indicated that both insecticidal and antimicrobial substances are present in the 10-kDa sieved filtrates. Proteins in the cultured filtrates were analyzed using SDS-PAGE electrophoresis. A protein band with 85 kDa of molecular weight was detected in the 100-kDa sieved filtrates while two bands with 22 and 25 kDa were found in the 10-kDa sieved filtrates. On the basis of coloration tests, most of the separated molecules showed amino acid structures. Furthermore, both exo- and endo-chitinases in the filtrates through 10-50 kDa sieves could be detected after reacting with different substrates, emitting fluorescence under the UV microscope. The concentration of LPS isolated from X. indica was ca. 3 x 105 EU/ml, causing ca. 93% mortality of G. mellonella larvae at 36 h, respectively. The LPS from X. indica resulted in ca. 7.67 mm of inhibition zone against a bacterium, B. subtilis and a fungus, B. cinerea, whereas that from Xenorhabdus nematophila caused ca. 8.00 and 5.33 mm of inhibition zone, respectively. In contrast, LPS from Escherichia coli which is also an intestinal bacterium produced only ca. 1.33 mm of inhibition zone against B. subtilis. Therefore, the LPS from X. indica could inhibit both bacterial and fungal growth. Electron micrographs showed a circular form of DNA structure in X. indica plasmids, its size being ca. 5,167 bp, with GC=39%, AT=61%, indicating an AT-rich DNA sequence. As a result from BLAST analysis, only 7 fragments contained similarly functional genes. It was also speculated that X. indica plasmids seem to be involved in cellular membrane formation, pathogenic hemolysin, glucose metabolism, spore germination, and others. However, further studies on many other unknown functional genes which are related to syntheses of amino acid sequence leading to these functions remain to be undertaken.
46
ČÁPOVÁ, Diana. "Nekrofágie u entomopatogenních hlístic". Master's thesis, 2017. http://www.nusl.cz/ntk/nusl-317440.
Testo completoAbstract (sommario):
The aim of the present study was to study the occurrence of scavenging behavior among different species and strains of entomopathogenic nematodes. Another part of the study was focused on scavenging of the selected entomopathogenic nematodes in insects killed by various non-native strains of Xenorhabdus bovinenii. Further aim was to investigate the interspecific competition of the selected entomopathogenic nematodes with the nematode Oscheius myriophila for dead hosts. The final aim was the search for possible toxicity of the selected X. bovienii strains against nematode Oscheius myriophila.
47
Wu, Shan-Cheng, e 吳山正. "Production of the entomopathogenic nematode, Steinernema carpocapsae, and its symbiotic bacterium, Xenorhabdus sp., and their pathogenicity to beet armyworm, Spodoptera exigua". Thesis, 1997. http://ndltd.ncl.edu.tw/handle/66141803108613193568.
Testo completoAbstract (sommario):
碩士國立中興大學
昆蟲學系
85
Production of the entomopathogenic nematode, Steinernema carpocapsae, and its symbiotic bacte- rium, Xenorhabdus spp., and their pathogenicity to the beet armyworm, Spodoptera exiguaShan-Cheng WuABSTRACTThe pure culture of the symbiotic bacterium, Xenorhabdus sp., of the entomopathogenic nematode, Steinernema carpocapsae, was applied to infect larvae of the beet armyworm, Spodoptera exigua, and was also incorporated into artificial diets for growing this nematode. The bacteria were cultured on nutrient agar plates by adding BTB and TTC. The primary form (PⅠ) showed blue colonies, whereas the secondary form (PⅡ) was red. After culturing the media turned from yellowish green into blue, and a light yellow halo appeared around the colony. In liquid culture with a large number of bacteria, it was observable that the culture media changed from golden yellow into milky yellow. After culturing by rolling granules on plates for 24 hr, the PⅡ count in suspension was 7.29×106 cells/ml. After culturing for 48 hr, the PⅠ count was only 0.54×106 cells/ml, indicating that PⅡ grows faster than P Ⅰ. The LC50 value of PⅠ to S. exigua larvae was 64.71 cells/ ml, while that of PⅡ was 128.71 cells/ml, indicating that PⅠ is more virulent than PⅡ. The LC50 value of PⅠ was 15.76 hr, P Ⅱ being 27.33 hr. The dog food （Pedigreea crunchy bites） was adopted to be the basal diet for growing S. carpocapsae. The nematode production was ca. 6.09×104 IJs/g by adding 10% beef extracts and 10% cholesterol, and was ca. 6.05×104 IJs/g by adding 10% peptone and 10% cholesterol. Addition of symbiotic bacteria to the dog food containing 10% peptone and 10% cholesterol was beneficial for growing nematodes, the production being 7.32×104IJs/g. The infective juveniles from living insects with the inoculum of 50 IJs/ml resulted in 100% S. exigua mortality, whereas those from artificial diets containing 10% peptone or beef extracts, 10% cholesterol and symbiotic bacteria caused 83-84% mortality. It is thus indicated that the infective juveniles by artificial diets are inferior to those grown in living insects. Therefore, the nematodes grown in living insects are more pathogenic and active than those on artificial diets. Refrigeration of the pupal capsules containing nematodes for 10-20 days showed that IJs from the pupal capsules stored for 10 days caused 91.61% larval mortality of S. exigua. Increase in storage time might reduce pathogenicity of the pupal capsules to S. exigua larvae. Enclosure of 104 IJs/ml nematodes in the black film box containing vermiculites resulted in 83.33% larval mortality of S. exigua, while 103 IJs/ml and 102 IJs/ml caused 61.67% and 72.50%, respectively. The results indicated that application of the vermiculite containing film boxes with more than 102 IJs/ml nematodes to the ground surface may be promising for controlling the beet armyworm.
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Ribeiro, Carlos. "Efeito sobre os hemócitos de insectos de um factor citotóxico produzido pela bactéria Xenorhabdus nematophila (Enterobacteriaceae) : pesquisa de actividades citotóxicas : purificação e caracterização da citotoxina". Doctoral thesis, 2002. http://hdl.handle.net/10400.3/199.
Testo completoAbstract (sommario):
Tese de Doutoramento em Biologia, especialidade de Biologia Celular e MolecularApós uma actualização bibliográfica que faz o objecto da primeira parte e após a descrição dos meios técnicos e métodos na segunda parte, os resultados do nosso trabalho de investigação são expostos na terceira parte subdividida em quatro grandes capítulos. 1.- No primeiro destes capítulo fazemos um estudo dos hemócitos das espécies de lepidópteros que foram escolhidos para este estudo Mythimna unipuncta e Spodoptera littoralis ambos pertencentes à família Noctuidae. As grandes funções desempenhadas por cada um dos tipos celulares são descritas assim como o comportamento dos hemócitos in vitro. Isto permitir-nos-á descrever o estabelecimento e a afinação de um teste original de utilização dos hemócitos para o estudo das relações bactérias-insectos, que será utilizado no resto do nosso trabalho. Os resultados deste capítulo estão, em parte, reportados na nossa publicação n°1. 2.- O segundo capítulo é consagrado à evidenciação e descrição detalhada das actividades citotóxicas desenvolvidas pelo complexo nematobacteriano, principalmente, pela bactéria. São caracterizados cada um dos diferentes factores responsáveis pelas actividades citotóxicas. Este capítulo permitir-nos-á escolher, de entre todos os factores encontrados, aquele que nos pareceu o mais importante participante na depressão das reacções imunitárias induzidas pela bactéria. Será sobre o factor escolhido que incidirão os estudos desenvolvidos nos capítulos seguintes. Os resultados expostos neste quarto capítulo são os reportados nas nossas publicações n° 2 e 3. 3.- O terceiro capítulo é consagrado à purificação e à descrição bioquímica do principal factor que nós chamámos α-Xenorhabdolisina. Foram efectuados numerosos ensaios para esta purificação mas descreveremos essencialmente o método que nos permitiu obter uma fracção pura. Mostraremos que esta citotoxina é uma molécula do grupo muito importante das toxinas de origem bacteriana, que era totalmente desconhecida antes do nosso estudo. É a partir desta fracção totalmente purificada que podemos efectuar a continuação do nosso trabalho de investigação. 4.- No quarto capítulo descreveremos os efeitos deste factor citotóxico sobre as células alvo que são os hemócitos. Este estudo foi feito em microscopia óptica e electrónica. Permitiu-nos mostrar que em função das condições de aplicação, a α-Xenorhabdolisina poderia induzir quer a necrose quer a apoptose dos Na última parte substantiva do nosso trabalho está consagrado à discussão geral e conclusões, na qual faremos o estudo crítico dos resultados obtidos. Mostraremos que o factor citotóxico que purificámos e estudámos pode participar na depressão das reacções de imunidade celulares desenvolvidas pelo insecto. Discutiremos, em particular, a importância desta citotoxina no conjunto dos factores produzidos pela bactéria X. nematophila para colonizar o meio insecto. A finalizar apresentaremos a lista de referências bibliográficas consultadas no decurso do trabalho.
Apoio financeiro do Ministério para a Ciência e a Tecnologia, através da Fundação para a Ciência e a Tecnologia (FCT) e do Fundo Social Europeu (FSE), no âmbito do III Quadro Comunitário de Apoio, na forma de uma Bolsa de Doutoramento, PRAXIS XXI (BD/13935/97).