Дисертації з теми "Bacterial symbiont"
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Russell, Shelbi Lianne. "Mode and Fidelity of Bacterial Symbiont Transmission and Its Impact on Symbiont Genome Evolution." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493576.
Повний текст джерелаАнотація:
Mutualistic symbioses have enabled the colonization of novel habitats and niches in a large array of eukaryotic and bacterial taxa. Reliable mechanisms of symbiont transmission between host generations are necessary to stabilize these associations over evolutionary time. Historically, symbionts have been categorized as either vertically transmitted from the parents to offspring or horizontally transmitted through the environment. The route between hosts influences how symbiont populations are connected between hosts and between geographic localities. Over evolutionary time vertical transmission leads to gene loss and genome erosion. Growing evidence from diverse associations suggests that modes utilizing both horizontal and vertical strategies exist, raising the question of how these “mixed modes” influence symbiont genome evolution. The overarching goal of my dissertation was to determine whether the mode of symbiont transmission in an obligate mutualism is consistent over evolutionary time and what impact transmission mode fidelity has on symbiont genome evolution. To test these questions, I used the chemosynthetic symbiosis between the marine bivalve Solemya velum and its gammaproteobacterial symbionts, which has been reported to transmit its symbionts vertically through the ovary, but bears none of the genomic hallmarks of strict vertical transmission.
In this work, I used population genomics of S. velum subpopulations sampled from five localities along the New England coast, from Massachusetts to North Carolina, to test for evidence of horizontal transmission in the evolutionary history of this species. These analyses revealed that symbionts and mitochondria do not exhibit concordant genealogies, divergent symbiont lineages have come into contact and recombined, and symbiont genomes have experienced large-scale structural changes mediated by mobile elements and horizontal gene transfer. In total, these lines of evidence indicate that a substantial amount of horizontal transmission has occurred in the recent history of this association. The vertical transmission route through host tissues was characterized via in situ hybridization to symbiont 16S rRNA in adult host tissues and by qPCR of the rhlE gene in spawned eggs. These data showed that symbionts are present at low abundance in the ovary, associated with the supportive cells and mature oocytes, and each spawned egg contains approximately 50-100 copies of the symbiont genome. Lastly, I tested for evidence of mixed transmission modes in symbiont populations contained within host tissues (each host gill contains more than a billion symbiont cells), by deep-coverage whole genome sequencing. Using a novel variant-calling procedure, I detected low amounts of genetic variation among symbiont genomes within a host relative to between hosts. However, the variant sites that were present were correlated in position along the genome, present on the same chromosome, and segregating in the symbiont population at large, suggesting that these variants arose via recombination with a variant symbiont genotype introduced by horizontal transmission.
In total, this work supports the existence of mixed transmission modes in symbiotic associations and indicates they have distinct consequences for symbiont evolution. Mixed modes may provide a best-of-both-worlds strategy to ensure that hosts acquire symbionts every generation while maintaining opportunities for recombination and acquisition of novel genetic elements. These results are relevant to understanding the impact of symbiont transmission mode on genome evolution in associations ranging from mutualisms to pathogenic infections.Biology, Organismic and Evolutionary
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Beinart, Roxanne Abra. "Linking bacterial symbiont physiology to the ecology of hydrothermal vent symbioses." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11270.
Повний текст джерелаАнотація:
Symbioses between prokaryotes and eukaryotes are ubiquitous in our biosphere, nevertheless, the effects of such associations on the partners' ecology and evolution are poorly understood. At hydrothermal vents, dominant invertebrate species typically host bacterial symbionts, which use chemical energy to fix carbon to nourish their hosts and themselves. In this dissertation, I present evidence that symbiont metabolism plays a substantive, if not major, role in habitat use by vent symbioses. A study of nearly 300 individuals of the symbiotic snail Alviniconcha sp. showed specificity between three host species and three specific symbiont phylotypes, as well as a novel lineage of Oceanospirillales. Additionally, this study revealed a structured distribution of each Alviniconcha-symbiont combination across ~300 km of hydrothermal vents that exhibited a gradient in geochemical composition, which is consistent with the physiological tendencies of the specific symbiont phylotypes. I also present a comparison of the in situ gene expression of the symbionts of Alviniconcha across that same geochemical gradient, which further implicates symbiont energy and nitrogen metabolism in governing the habitat partitioning of Alviniconcha. Finally, I present data that allies productivity and sulfur metabolism in three coexisting vent symbioses, demonstrating specific interaction with the environment. Three symbioses, namely the snails Alviniconcha and Ifremeria, and the mussel Bathymodiolus, are found around vents with differing concentrations of sulfide, thiosulfate and polysulfide. Using high-pressure, flow-through incubations and stable isotopic tracers, I quantified symbiont productivity via sulfide and thiosulfate oxidation, and provided the first demonstration of thiosulfate-dependent autotrophy in intact hydrothermal vent symbioses. I further demonstrated that vent symbioses can excrete thiosulfate and/or polysulfides, implicating them in substantively influencing the sulfur chemistry of their habitats. In summary, this dissertation demonstrates the importance of symbiont physiology to the ecology of prokaryote-eukaryote symbioses by revealing that symbiont activity may be critically important to the distribution of symbioses among specific niches, as well as can alter the geochemical environment through uptake and excretion of chemicals.
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Peterson, Brittany F., and Michael E. Scharf. "Metatranscriptome analysis reveals bacterial symbiont contributions to lower termite physiology and potential immune functions." BIOMED CENTRAL LTD, 2016. http://hdl.handle.net/10150/621516.
Повний текст джерелаАнотація:
Background: Symbioses throughout the animal kingdom are known to extend physiological and ecological capabilities to hosts. Insect-microbe associations are extremely common and are often related to novel niche exploitation, fitness advantages, and even speciation events. These phenomena include expansions in host diet, detoxification of insecticides and toxins, and increased defense against pathogens. However, dissecting the contributions of individual groups of symbionts at the molecular level is often underexplored due to methodological and analytical limitations. Termites are one of the best studied systems for physiological collaborations between host and symbiota; however, most work in lower termites (those with bacterial and protist symbionts) focuses on the eukaryotic members of this symbiotic consortium. Here we present a metatranscriptomic analysis which provides novel insights into bacterial contributions to the holobiont of the eastern subterranean termite, Reticulitermes flavipes, in the presence and absence of a fungal pathogen. Results: Using a customized ribodepletion strategy, a metatranscriptome assembly was obtained representing the host termite as well as bacterial and protist symbiota. Sequence data provide new insights into biosynthesis, catabolism, and transport of major organic molecules and ions by the gut consortium, and corroborate previous findings suggesting that bacteria play direct roles in nitrogen fixation, amino acid biosynthesis, and lignocellulose digestion. With regard to fungal pathogen challenge, a total of 563 differentially expressed candidate host and symbiont contigs were identified (162 up-and 401 downregulated; a/FDR = 0.05) including an upregulated bacterial amidohydrolase. Conclusions: This study presents the most complete bacterial metatranscriptome from a lower termite and provides a framework on which to build a more complete model of termite-symbiont interactions including, but not limited to, digestion and pathogen defense.
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Gibson, Cara. "Heritable Microbial Endosymbionts in Insects: Insights from the Study of a Parasitic Wasp and its Cockroach Host." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195875.
Повний текст джерелаАнотація:
Endosymbiosis is a pervasive phenomenon that has been a powerful force in insect evolution. In many well studied insect-bacterial associations, the bacteria can serve as reproductive manipulators, nutritional mutualists or defenders of their hosts. Fungi are also frequently associated with insects, and initial estimates suggest that these fungi are hyperdiverse. Saving a handful of examples, however, the functions of these fungi within insect hosts are largely unknown. This dissertation begins with a review that lays the conceptual groundwork for understanding bacterial and fungal endosymbiosis in insects. I make predictions about why one versus the other microbe might serve the insect, given any unique physiological, ecological or evolutionary conditions. I then aim to derive insights about microbial symbiosis by focusing on a particular system, that of brownbanded cockroaches, Supella longipalpa (Blattaria: Blattellidae) and their specialist wasp parasitoids, Comperia merceti (Hymenoptera: Encyrtidae). Here, I identify the symbiotic community of these two insects by using both culture-dependent and independent methods to characterize the vertically transmitted bacterial and fungal associates. Finally, I show that a heritable fungus in C. merceti, long presumed to be a mutualist, is parasitic under laboratory conditions: infected wasps incur fitness costs for housing the fungal symbiont relative to uninfected wasps. Additionally, although the fungus is not horizontally transmitted sexually, it is readily horizontally transmitted from the offspring of infected females to those of uninfected females that are using the same host.
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Hansen, Thorsten. "IDENTIFYING MECHANISMS OF HOST PLANT SPECIALIZATION IN APHIS CRACCIVORA AND ITS BACTERIAL SYMBIONTS." UKnowledge, 2018. https://uknowledge.uky.edu/entomology_etds/42.
Повний текст джерелаАнотація:
Many insects form close relationships with microbial symbionts. Insect symbionts can provide novel phenotypes to their hosts, including influencing dietary breadth. In the polyphagous cowpea aphid, Aphis craccivora, the facultative symbiont Arsenophonus improves aphid performance on one host plant (locust), but decreases performance on other plants. The goal of my thesis was to investigate the mechanism by which Arsenophonus facilitates use of locust. First, I assembled an Aphis craccivora-Arsenophonus-Buchnera reference transcriptome to conduct RNAseq analysis, comparing gene expression in aphids feeding on locust and fava, with and without Arsenophonus infection. Overall, few transcripts were differentially expressed. However, genes that were differentially expressed mapped to a variety of processes, including metabolism of glucose, cytoskeleton regulation, cold and drought regulation, and B-vitamin synthesis. These results imply that Arsenophonus is producing B-vitamins, which might be deficient in locust. In a second set of experiments, I used qPCR to test whether symbiont function across host plants might be mediated by bacterial titer. I measured relative Arsenophonus abundance across plants, and found Arsenophonus titer was variable, but generally greater on locust than fava. In summary, my results suggest that Arsenophonus synthesis of B-vitamins should be further investigated and may be mediated by bacterial titer.
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Wilson, Alex, Helen Dunbar, Gregory Davis, Wayne Hunter, David Stern, and Nancy Moran. "A dual-genome microarray for the pea aphid, Acyrthosiphon pisum, and its obligate bacterial symbiont, Buchnera aphidicola." BioMed Central, 2006. http://hdl.handle.net/10150/610396.
Повний текст джерелаАнотація:
BACKGROUND:The best studied insect-symbiont system is that of aphids and their primary bacterial endosymbiont Buchnera aphidicola. Buchnera inhabits specialized host cells called bacteriocytes, provides nutrients to the aphid and has co-speciated with its aphid hosts for the past 150 million years. We have used a single microarray to examine gene expression in the pea aphid, Acyrthosiphon pisum, and its resident Buchnera. Very little is known of gene expression in aphids, few studies have examined gene expression in Buchnera, and no study has examined simultaneously the expression profiles of a host and its symbiont. Expression profiling of aphids, in studies such as this, will be critical for assigning newly discovered A. pisum genes to functional roles. In particular, because aphids possess many genes that are absent from Drosophila and other holometabolous insect taxa, aphid genome annotation efforts cannot rely entirely on homology to the best-studied insect systems. Development of this dual-genome array represents a first attempt to characterize gene expression in this emerging model system.RESULTS:We chose to examine heat shock response because it has been well characterized both in Buchnera and in other insect species. Our results from the Buchnera of A. pisum show responses for the same gene set as an earlier study of heat shock response in Buchnera for the host aphid Schizaphis graminum. Additionally, analyses of aphid transcripts showed the expected response for homologs of known heat shock genes as well as responses for several genes with unknown functional roles.CONCLUSION:We examined gene expression under heat shock of an insect and its bacterial symbiont in a single assay using a dual-genome microarray. Further, our results indicate that microarrays are a useful tool for inferring functional roles of genes in A. pisum and other insects and suggest that the pea aphid genome may contain many gene paralogs that are differentially regulated.
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König, Sten. "The bacterial symbiont in the shallow water lucinids Codakia orbicularis and C. orbiculata analyzed by physiological proteogenomics." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066700.
Повний текст джерелаАнотація:
Les bivalves côtiers Codakia orbicularis et C. orbiculata, de la famille des Lucinidae, abritent des Gammaprotéobactéries endosymbiotiques sulfo-oxydantes dans leurs branchies. Ces deux bivalves vivent dans les herbiers à Thalassia testudinum et hébergent la même bactérie symbiotique selon les analyses effectuées à partir des séquences d’ADNr 16S. Lors de période de stabulation, la population bactérienne symbiotique décroit alors qu’il n’y a pas, dans le même temps, de relargage des symbiotes observé. Des analyses en cytochimie ont montré une forte activité d’enzymes lysosomales lors de ces épisodes de privation de nourriture et de soufre. Il a ainsi été montré que les symbiotes peuvent servir directement de source de nourriture aux bivalves pour survivre lors de ces périodes de crise. Le transfert de carbone des symbiotes vers l’hôte peut être flexible et pourrait consister en un simple transfert de matière organique ou "milking", dans des conditions normales de nutrition et de digestion des symbiotes et devenir du "farming", dans des conditions de stabulation. Jusqu’à ce jour, le symbiote reste non cultivable. De ce fait, l’utilisation de techniques indépendantes de la culture comme les approches –omics ont été mises en place pour étudier la physiologie de cette bactérie symbiotique. Le génome du symbiote a été analysé par Next Generation Sequencing (NGS) permettant ainsi d’obtenir les bases du protéome et ainsi de pouvoir analyser la physiologie du symbiote. Dans ce travail, le protéome des bactéries a été analysé sous différentes conditions. L’oxydation des sulfures est une des voies métaboliques clés du symbiote de Codakia. Cette voie fait très probablement appel au système Sox périplasmique, ainsi qu’à une sulfite réductase cytoplasmique (DsrAB), une APS réductase (AprAB) et une ATP sulfurylase (SopT). De plus, deux autres enzymes additionnelles d’oxydation des sulfures ont pu être mises en évidence dans l’espace périplasmique du symbiote telle que la quinone réductase (Sqr) et la sulfide déhydrogénase (FccAB). Les gènes des enzymes du cycle de Calvin Benson Bassham (CBB) ne semblent pas être tous présents dans le génome du symbiote. Les protéines de la RuBisCO sont abondamment exprimées. Il semblerait que la régénération du ribulose-1,5-bisphosphate soit effectuée de façon non conventionnelle via une phosphofructokinase PPi-dépendante. Une autre caractéristique du CBB est qu’il y a deux formes différentes de RuBisCO codées dans le génome du symbiote. Les deux formes sont exprimées en même temps, mais la forme I de la RuBisCO est 50 fois plus exprimée que la forme II. En plus de la vie autotrophique, plusieurs gènes nécessaires à une vie hétérotrophique sont présents dans le génome. Dans le protéome, les enzymes de la glycolyse et du cycle TCA sont faiblement exprimées. Les protéines du métabolisme du glycogène ont également été identifiées dans le protéome. De plus, plusieurs types de transporteurs comme ABC, TRAP et PTS sont présents dans le génome et certaines formes d’expression de ces transporteurs ont pu être suspectées, y compris lors de la vie intracellulaire du symbiote. De façon inattendue, un groupe de gènes nif est présent dans le génome permettant la fixation de l’azote atmosphérique par le symbiote. Les protéines codées par les gènes clés, comme la nitrogénase NifH/K/D, ont été abondamment trouvées dans le protéome. De plus, l’analyse du protéome montre une régulation forte de ces protéines dans des conditions de stabulation du bivalve hôte. La rubrerythrine est fortement exprimée et servirait à protéger la nitrogénase de l’oxygène au sein des bacteriocytes. L’endosymbiote bactérien code également pour un système de sécrétion de type 6 (T6SS) pour le transport de molécules bactériennes effectrices à travers les membranes du cytoplasme de la cellule hôte et jouerait un rôle possible de communication directe avec l’hôteThe shallow water bivalves Codakia orbicularis and Codakia orbiculata, both belonging to the family Lucinidae, harbor endosymbiotic sulfur-oxidizing gamma-Proteobacteria in their gills. The bivalves live in seagrass beds of Thalassia testudinum and harbor the same bacterial symbionts according to 16S rDNA sequence analysis. During starvation, the symbiont population decreases while no release of symbionts were observed. We observed lysosomal enzyme activity during sulfide and food starvation with cytochemical staining methods. We suggest that the host uses symbionts as a nutrient source to survive a hunger crisis. The carbon transfer from the symbionts to the host could be flexible and could consist in transfer of organic matter, "milking", under normal feeding conditions and digestion of the symbionts, "farming", under starved conditions. Until now the symbiont alone is not cultivable. Therefore, cultivation-independent techniques, like -omics approaches were used to analyze the physiology of the symbiont. Next generation sequencing (NGS) was employed to sequence the genomes of symbionts from both hosts, display the backbone for proteomics. The soluble- and membrane-associated symbiont proteomes were analyzed during different conditions. The oxidation of sulfide is one key metabolic pathway of the Codakia symbiont, most probably using the periplasmic Sox-system, a cytoplasmatic sulfite reductase (DsrAB), an APS reductase (AprAB) and an ATP sulfurylase (SopT). Furthermore, indications for two additional putative sulfide oxidation systems in the periplasmic space, the sulfide quinone reductase (Sqr) and the sulfide dehydrogenase (FccAB), could be found. The Calvin Benson Bassham cycle (CBB) of the symbiont is not completely encoded in the genome. The key genes, RuBisCO, are abundantly expressed. It is assumed that the regeneration of the ribulose-1,5-bisphosphate is performed unconventionally via a PPi-dependent phosphofructokinase. Another feature of the CBB is that two different forms of RuBisCO are encoded in the genome. Both are expressed at the same time, but RuBisCO form I is about 50x times more expressed. Additional to the autotrophic lifestyle, all genes for the heterotrophic lifestyle are encoded in the genome. In the proteome, the enzymes related to glycolysis and TCA-cycle were low expressed. Interestingly, proteins for glycogen metabolism were identified in the proteome. Additionally, several types of transporters like ABC, TRAP and PTS are encoded in the genome. In the proteome several indications were found for an expression of these transporters, even in the endosymbiotic lifestyle. Unexpectedly, in the genome a nif gene cluster is encoded for gaseous nitrogen fixation as ammonium source. The key genes, the nitrogenase NifH/K/D, were abundantly identified in proteome. Further, the proteome analyses indicate a strictly down-regulation of these proteins under starvation conditions. Rubrerythrin, a strongly expressed protein and is predicted to protect the nitrogenase against oxygen stress. The bacterial endosymbionts encode a specialized secretion system type 6 (T6SS) for the transport of bacterial effector molecules through the membranes to the host cytoplasm and display one possibility for a direct "communication" with the host. In summary, genomics and proteomics analyses of the Codakia symbiont improved the knowledge about the metabolism of the symbiont in lucinid bivalves.. The genomics and proteomics data generated in this study can be used as a basis for further in-depth analyses of the physiology of the symbionts and interaction with the host
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Flórez, Laura Victoria [Verfasser], Martin [Gutachter] Kaltenpoth, Christian [Gutachter] Hertweck, and Martha S. [Gutachter] Hunter. "Burkholderia as bacterial symbionts of Lagriinae beetles : symbiont transmission, prevalence and ecological significance in Lagria villosa and Lagria hirta (Coleoptera: Tenebrionidae) / Laura Victoria Flórez ; Gutachter: Martin Kaltenpoth, Christian Hertweck, Martha S. Hunter." Jena : Friedrich-Schiller-Universität Jena, 2017. http://d-nb.info/117760261X/34.
Повний текст джерела
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Wilkinson, Peter Graham. "Characterisation of the bacterial flora associated with the grey field slug Deroceras reticulatum and assessment of its suitability as a target for biological control." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5276.
Повний текст джерелаАнотація:
The field slug Deroceras reticulatum is a major pest in UK agriculture and amidst growing concern and regulatory pressures surrounding chemical molluscicides, innovation is required to advance the current repertoire of slug controls. This study set out to investigate the bacteria associated with D. reticulatum to assess their importance to the slug and potential as a target for biological control. Slug gut bacterial isolates identified using the phenotypical API system (BioMérieux) and 16S rRNA gene sequencing, were mainly soil-dwelling organisms of the phyla Proteobacteria and Bacteriodetes some of which may be important in human or plant disease. A ribosomal intergenic spacer analysis (RISA) was developed to study microbial communities in the slug gut. Slugs had an average species richness of 12 and comparing the bacterial communities in slugs from different locations yielded a mean similarity of 0.159 (Jaccard index) which was significantly lower than similarity indices of slugs collected within a single location (Mean Jaccard index 0.205, p<0.001, ANOVA). Cloning and sequencing of RISA bands common to slugs and slug eggs, but absent from the surrounding soil and plants identified bacteria for future investigation as potential beneficial symbionts. Bacteria extracted from the slug gut were tested for sensitivity to 16 antibiotics and greatest inhibition of growth was observed for chloramphenicol, gentamicin and tetracycline. These antibiotics administered to slugs by feeding and injection caused a reduction in gut-associated bacteria in plate counts, and in bacterial 16S rDNA quantities estimated by real-time quantitative PCR. Field collected D. reticulatum has a large transient gut bacterial population which is reduced upon starvation to a low background level. No significant detrimental effect of antibiotic treatment on the fitness and survival of the slugs was seen, in some instances control slugs suffered greater mortality than slugs that had been injected with antibiotic. Slugs that died during bioassays had a significantly greater amount of bacterial 16S rDNA in their gut than slugs that were sacrificed as healthy individuals suggesting the presence of a bacterial pathogen. This study has found little evidence that a bacterial symbiont may exist and be important for optimal fitness and survival of D. reticulatum, but insight into slug associated bacteria will be valuable in the direction of future studies in this field.
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Andam, Cheryl Marie Palacay. "Role of lateral gene transfer in the evolution of legume nodule symbionts." Diss., Online access via UMI:, 2007.
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BLACUTT, JACOB. "GENOME ANALYSIS OF BACTERIAL SYMBIONTS ASSOCIATED WITH HAPTOPHYTE PRYMNESIUM PARVUM." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/612639.
Повний текст джерелаАнотація:
Prymnesium parvum is an ecologically and commercially significant organism due to
its propensity to form large toxic algal blooms. However, the combinations of factors that
determine whether or not an algal bloom will form are still unknown. The purpose of this
thesis was to identify and characterize the bacterial symbionts of Prymnesium parvum,
which might help induce the formation of the algal blooms. In this experiment many
bacteria were shown to be in or around Prymnesium parvum during an algal bloom.
Additionally, after further analysis the majority of the genome of one species was
assembled in addition to its associated plasmid. Based on 16s rDNA data this species is
related very closely to Erythrobacter longus strain OCh101 and Erythrobacter litoralis
HTCC2594, while the proteins in the plasmid relate it to a similar plasmid seen in
Dinoroseobacter shibae DFL12. This data provides evidence that some of the bacteria found
within the sample could be contributing to the formation of algal blooms. To further
understand the bacterial role in Prymnesium parvum more analysis needs to be done with
these suspected bacteria.
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Oliver, Kerry M. "The role of pea aphid bacterial symbionts in resistance to parasitism." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1031%5F1%5Fm.pdf&type=application/pdf.
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McGinley, Susan. "Better Parasitic Wasps for Biological Control: Bacterial Symbionts Make a Difference." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006. http://hdl.handle.net/10150/622173.
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Hanekom, Thea. "Screening bacterial symbionts of marine invertebrates for ribosomally synthesized natural products." University of the Western Cape, 2016. http://hdl.handle.net/11394/5441.
Повний текст джерелаАнотація:
>Magister Scientiae - MScPharmaceutical research and development strategies rely on the constant discovery of novel natural products as potential drugs. Recent studies have shown that the microorganisms associated with sponges are the true producers of some previously isolated compounds. This study created a large collection of bacterial symbionts associated with the South African marine sponge, Hamacantha esperioides. The bioactivity assays performed, showed that 44 isolates produced compounds with antimicrobial or anti-inflammatory activity. The successful identification of novel species that produce potential natural products highlights the importance of cultivation-dependent methods. To further screen for natural products, a cultivation-independent approach was used. A sequenced-based method, based on the biosynthetic genes of polytheonamide, was developed to screen for proteusins in sponge metagenomic DNA and the genomes of bacterial symbionts. The degenerate primers could amplify the targeted genes from DNA known to contain homologues. Evaluation of the primers' specificity showed non-specific amplification of genes, some containing similar conserved domains as the target genes. This study demonstrated that the use and development of cultivation-dependent and -independent screens are important for the discovery of novel natural products from the symbiotic bacteria of South African sponges.
National Research Foundation (NRF)
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Geniez, Sandrine. "Investigation of Wolbachia symbiosis in isopods and filarial nematodes by genomic and interactome studies." Thesis, Poitiers, 2013. http://www.theses.fr/2013POIT2277/document.
Повний текст джерелаАнотація:
Les Wolbachia sont des alpha-proteobactéries présentes chez de nombreux arthropodes et nématodes filaires. Ces bactéries héritées maternellement induisent chez leurs hôtes des phénotypes allant du parasitisme au mutualisme, avec le long de ce continuum des phénotypes tels que la féminisation (F), l'incompatibilité cytoplasmique (IC) ou la mort des mâles. Wolbachia est ainsi un modèle particulièrement intéressant pour étudier les différents types de relations symbiotiques.Chez Brugia malayi, comme pour les autres nématodes filaires, Wolbachia vit en symbiose obligatoire avec son hôte. L'élimination de la bactérie par des traitements antibiotiques entraîne une perte de fertilité voire la mort du nématode. Chez l'isopode terrestre Armadillidium vulgare, Wolbachia induit la féminisation des mâles génétiques en femelles fonctionnelles entraînant des biais de sex-ratio vers les femelles dans la descendance.Pour comprendre les mécanismes impliqués dans ces deux symbioses, nous avons mis au point une nouvelle méthode de capture pour isoler l'ADN de Wolbachia et séquencer 8 souches de Wolbachia d'isopodes (F et IC). Une étude de génomique comparative a permis d'établir un premier pan-génome des bactéries du genre Wolbachia et d'identifier 2, 5 et 3 gènes présents seulement chez les souches mutualistes, féminisantes ou induisant la mort des mâles. L'expression des gènes potentiellement impliqués dans la féminisation ou le mutualisme a été étudiée au cours du développement de l'hôte. L'étude de l'interactome protéique bactérie-hôte a ensuite été initiée en utilisant comme appât des protéines bactériennes à domaines eucaryotes en vue d'identifier les cibles de Wolbachia chez l'hôteBacteria of the genus Wolbachia are gram-negative alpha-proteobacteria present in many arthropods and filarial nematodes. These obligate intracellular bacteria are maternally inherited and induce a large number of phenotypes across the symbiosis continuum from mutualism to parasitism, including feminization (F), cytoplasmic incompatibility (CI) or male killing. Studying Wolbachia symbioses is therefore of particular interest in the investigation of symbiotic relationships.In Brugia malayi and other filarial nematodes, they are obligate leading to a loss of worm fertility, and eventual death upon their depletion with antibiotic. In arthropods, they rather are parasitic. In the isopod crustacean Armadillidium vulgare they cause feminization when present: genetic males develop as functional female leading to female biased sex-ratio progenies.In order to understand the molecular mechanisms of these two symbioses, we set up a new capture procedure to catch Wolbachia DNA and performed whole-genome sequencing on 8 Wolbachia strains, symbionts of isopods (F & CI). Comparative genomics led to the establishment of the Wolbachia pan-genome as well as the identification of phenotype related gene patterns. We identified 2, 5 and 3 genes that are only found in mutualist, feminizing and male killing strains, respectively. Expression of genes potentially involved in feminization and mutualism were also analyzed throughout host post-embryonic development. Host-symbiont interactome approach was then initiated by protein-protein interaction studies using bacterial proteins with eukaryote like motifs as bait in order to identify Wolbachia host targets involved in symbiosis
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Scates, Sara Stuart. "Symbiont-Mediated Modification of Mosquitocide Toxicity in the Dengue Vector, Aedes aegypti." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/64171.
Повний текст джерелаАнотація:
The incidence of mosquito-borne human diseases is increasing worldwide, with effective chemical control limited due to widespread insecticide resistance in the insect. Recent evidence also suggests that bacterial symbionts of mosquitoes, known to be essential in nutritional homeostasis and pathogen defense, may play a significant role in facilitating mosquitocide resistance. Here, I examined the metabolic detoxification and toxicity of two mosquitocides, propoxur and naled, and the capacity of bacterial symbionts to modify the detoxification of the mosquitocides and, thus, alter their toxic action in the yellow fever mosquito, Aedes aegypti. The insecticide synergists piperonyl butoxide (PBO), triphenyl phosphate (TPP), and S,S,S-tributyl phosphorotrithioate (DEF) were used to examine the metabolic detoxification and toxic action of the two mosquitocides in mosquito larvae. A significant increase in the toxicity of propoxur was observed when applied in combination with PBO; however, there was no corresponding decrease in AChE activity. Naled applied in combination with PBO resulted in a decrease in anticholinesterase activity (higher residual AChE activity) and a subsequent decrease in toxicity of the insecticide. This suggests that esterases play a major role in the metabolic detoxification of both insecticides in mosquito larvae. The acute toxicities of naled and propoxur to Ae. aegypti larvae were also studied following a reduction of bacterial symbionts with the broad-spectrum antibiotics gentamycin, penicillin, and streptomycin. Antibiotic-treated mosquito larvae showed increased susceptibility and a reduction in cytochrome P450 monooxygenase and general esterase activities when treated with naled and propoxur. A reduction of bacteria in mosquito larvae treated with broad-spectrum antibiotics, therefore, appears to affect the metabolic detoxification of standard-use mosquitocides, such as propoxur and naled. The results also suggest that the bacteria themselves may contain metabolic detoxification enzymes that are functionally similar to those in the mosquito larvae. Additional experiments, however, are needed to fully elucidate the contribution of bacterial symbionts in Ae. aegypti larvae in the metabolic detoxification of mosquitocides.Master of Science in Life Sciences
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Young, Simon. "Genetic features of Sodalis glossinidius, a symbiont bacterium of tsetse flies." Thesis, University of Glasgow, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274255.
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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.
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Klein, Timothy Matsiko Ninsiima. "The isolation and characterisation of novel natural products from marine bacterial symbionts." University of the Western Cape, 2015. http://hdl.handle.net/11394/4747.
Повний текст джерелаАнотація:
>Magister Scientiae - MScDrug-resistant infections are a global health crisis and drastically hinder the treatment options to effectively combat disease. Today, natural products remain an important source of novel drug candidates. Micro-organisms, in addition to being a source of bioactive natural products, represent a sustainable source of these compounds. As the marine environment is largely underexplored, the oceans represent a potential source of novel NPs. This study aimed at the discovery of novel NPs from bacteria associated with novel marine invertebrate species endemic to the South African coast, including a sponge Spongia (Spongia) sp. 001RSASPN and a tunicate, Pseudodistoma africanum Millar, 1954. The methodology comprised of culture-dependent and culture-independent strategies. The former involved the isolation of bacteria associated with the invertebrate species and subsequent screening for anti-microbial activity against a panel of indicator strains including a multi-drug resistant E. coli strain. Anti-bacterial activity was detected in 6.1% and 4% of bacterial isolates from the sponge and tunicate isolates respectively. The culture-independent strategy involved the use of PCR to select bioactive strains likely to contain novel NRPS or PKS secondary metabolite pathways. An NRPS A- domain exhibiting low sequence identity (65%) to reference sequences in the NCBI database was amplified from isolate PE8-15, a strain belonging to the genus Bacillus. This predicted a novel NRPS pathway within this strain. In addition, this isolate exhibited the most diverse anti-microbial profile including anti-bacterial and anti-fungal activity (A.fumigatus ATCC 46645). Therefore, as the most promising candidate, the genome of PE8-15 was sequenced following which 10 secondary metabolite pathways including bacteriocins (5), NRPS (3), siderophore (1) and a terpene pathway were identified. The A-domain amplified from PE8-15 originated from Cluster 4, and NRPS pathway predicted to encode a lipopeptide. Lipopeptides are an important class of compounds with a range of industrial applications in the pharmaceutical, cosmetic as well as food industry. The identification of potentially novel secondary metabolite pathways from even well- studied groups of organisms demonstrates the importance of sequence-based methods in natural product discovery. Furthermore, this study highlights the South African coast as a rich source of microbial natural products and should be exploited further for drug discovery.
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Salerno, Jennifer L. "Transmission and Nutritional Contribution of Dual Bacterial Symbionts in Deep-Sea Mussels." W&M ScholarWorks, 2003. https://scholarworks.wm.edu/etd/1539626398.
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Treanor, David. "Symbionts in societies : the biology of Wolbachia in social insects." Thesis, University of Sussex, 2018. http://sro.sussex.ac.uk/id/eprint/76440/.
Повний текст джерелаАнотація:
Heritable bacterial symbionts are astonishingly common in insects, yet relatively little is known about how heritable symbionts influence the biology of social insects such as ants, bees, wasps and termites. In this thesis I investigate various aspects of the biology of heritable symbionts in social insects, principally focusing on the relationship between ants, the largest group of social insects, and the symbiont Wolbachia, the archetypal reproductive parasite. In Chapter 1, I begin by reviewing the biology of Wolbachia. In Chapter 2, I show that the sex, caste and size of an individual's colony determine the likelihood that it is infected with Wolbachia, and I provide correlational evidence that Wolbachia provides small increases in colony productivity in the ant Temnothorax crassispinus. In Chapter 3, I combine colony censuses and antibiotic treatment experiments, finding that Wolbachia neither distorts host sex ratios nor causes strong female mortality type mating incompatibilities in the ant Myrmica scabrinodis. In Chapter 4, I critically evaluate the theory that heritable symbionts should evolve to manipulate caste-fate in social insects, outlining three distinct evolutionary scenarios under which this might occur. In Chapter 5, I provide evidence for negative interactions between Wolbachia and both Spiroplasma and Arsenophonus in M. scabrinodis hosts, and I show that multiple unrelated strains of both Wolbachia and Spiroplasma occur across the Palaearctic. In Chapter 6, I show that one of two strains of Wolbachia infecting the ant Monomorium pharaonis was acquired by hybrid introgression. In Chapter 7, I find that ant species with limited queen dispersal are almost twice as likely to be infected with Wolbachia relative to other ant species, supporting the hypothesis that population structure influences the invasion ability of Wolbachia. Finally, in Chapter 8, I discuss the broader significance of my findings.
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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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Matcher, Gwynneth F., Samantha C. Waterworth, Tara A. Walmsley, Tendayi Matsatsa, Shirley Parker-Nance, Michael Trevor Davies-Coleman, and Rosemary Dorrington. "Keeping it in the family: coevolution of latrunculid sponges and their dominant bacterial symbionts." John Wiley and Sons Ltd, 2016. http://hdl.handle.net/10962/65603.
Повний текст джерелаАнотація:
publisher versionThe Latrunculiidae are a family of cold water sponges known for their production of bioactive pyrroloiminoquinone alkaloids. Previously it was shown that the bacterial community associated with a Tsitsikamma sponge species comprises unusual bacterial taxa and is dominated by a novel Betaproteobacterium. Here, we have characterized the bacterial communities associated with six latrunculid species representing three genera (Tsitsikamma, Cyclacanthia, and Latrunculia) as well as a Mycale species, collected from Algoa Bay on the South African southeast coast. The bacterial communities of all seven sponge species were dominated by a single Betaproteobacterium operational taxonomic unit (OTU0.03), while a second OTU0.03 was dominant in the Mycale sp. The Betaproteobacteria OTUs from the different latrunculid sponges are closely related and their phylogenetic relationship follows that of their hosts. We propose that the latrunculid Betaproteobacteria OTUs are members of a specialized group of sponge symbionts that may have coevolved with their hosts. A single dominant Spirochaetae OTU0.03 was present in the Tsitsikamma and Cyclacanthia sponge species, but absent from the Latrunculia and Mycale sponges. This study sheds new light on the interactions between latrunculid sponges and their bacterial communities and may point to the potential involvement of dominant symbionts in the biosynthesis of the bioactive secondary metabolites.
This research was supported by a SARChI grant from the South African National Research Foundation (NRF, GUN: 87583) and the Rhodes University Sandisa Imbewu Programme. S. C. W. was supported by an NRF Innovation PhD Scholarship and a Rhodes University Henderson PhD Scholarship. T. A. W. was supported by PhD Fellowships from the NRF and the German Academic Exchange Service (DAAD)
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Rolim, Adrian Augusto Sosa Gómez. "Microbiota intestinal e assinatura isotópica de adultos de Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) como marcadores para a identificação da fonte alimentar de imaturos." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/11/11146/tde-05012015-155654/.
Повний текст джерелаАнотація:
A correta adoção de medidas de manejo de resistência de insetos-pragas é motivo de preocupação constante, inclusive para as novas tecnologias disponíveis, como as plantas geneticamente modificadas para a expressão de toxinas da bactéria Bacillus thuringiensis (Bt). Portanto, para manter a eficiência das plantas-Bt comercialmente disponíveis, é preconizada a manutenção de áreas de refúgio (livres de plantas Bt) para evitar a rápida seleção de insetos resistentes. No caso de insetos polífagos, a determinação das áreas de refúgio pode levar em consideração a contribuição que fontes não-comerciais e/ou não-transgênicas têm na produção de adultos colonizadores que não sofreram seleção para o evento de transgenia de interesse. A identificação da fonte alimentar pode determinar a procedência de insetos e tornar mais eficiente e segura a implementação de zonas de refúgio e a determinação dos riscos de desenvolvimento de resistência pelo inseto-praga alvo. O objetivo deste trabalho foi o de avaliar o potencial de dois marcadores biológicos, a assinatura isotópica e a microbiota intestinal, para a identificação da fonte de alimento do imaturo pela análise de adultos de Spodoptera frugiperda (J.E. Smith) (Lepidoptera, Noctuidae), como subsídio para o monitoramento da origem de insetos migrantes em áreas de cultivo Bt para a adoção de estratégias adequadas de manejo de resistência. A análise isotópica de adultos foi realizada utilizando-se insetos criados em 12 plantas hospedeiras distintas, seis de metabolismo C3 e seis de metabolismo C4. Parte dos adultos provenientes dessa criação foram liofilizados, macerados e submetidos à análise isotópica para a determinação dos níveis de ?13C e ?15N. Amostras das plantas utilizadas na alimentação desses insetos também foram submetidas ao mesmo processo de análise. A outra parte dos adultos recémemergidos de S. frugiperda foi utilizada para a determinação da microbiota intestinal pela análise de região do gene do 16S rRNA após sequenciamento em plataforma 454. Os resultados da análise isotópica de carbono para as plantas utilizadas como fonte alimentar apresentaram médias entre -31,37? e -25,07? para plantas C3 e entre -13,03? e -12,26? para plantas C4. Adultos de S. frugiperda oriundos de lagartas criadas em plantas do grupo C3 apresentaram média de ?13C entre - 30,36? e -23,72?, enquanto aqueles do grupo C4 apresentaram média entre - 18,25? e -13,28?. O sequenciamento da microbiota via metagenômica produziu 126,970 sequências com cerca de 421 pb. O alimento influenciou substancialmente a diversidade da microbiota intestinal associada ao intestino de adultos, independentemente do metabolismo fotossintético da planta hospedeira. Análises comparativas de diversidade em que a abundância relativa dos diferentes componentes foi considerada (Unifrac ponderado) permitiu a distinção de praticamente todas as microbiotas. Foram identificadas várias UTOs exclusivamente associadas à microbiota intestinal de adultos provenientes de cada fonte de alimento, mas a maioria apresentou abundância relativa extremamente baixa. Apenas as UTOs 1199 e 2255 foram exclusivamente associados ao milho com abundância relativa superior a 2,5%.The correct insect resistant management has been a topic of constant concern, even for the newer technologies available, such as genetically modified crops expressing Bacillus thuringiensis (Bt) toxins. The use of refuge areas with non-Bt crops to avoid the fast selection for resistant insects is proposed for maintaining the efficiency of Bt-crops. The implementation of refuge areas for polyphagous insects can consider non-commercial and non-Bt crops as sources of susceptible insects. The identification of the food source used during immature development can make the implementation of refuge areas safer and more efficient and allow for better estimates of risk assessment for insect resistance development. The objective of this study is to determine the potential use of, the isotopic signature and gut microbiota of adults as biological markers to allow for the identification of the food source during the larval stage of Spodoptera frugiperda (J.E. Smith) (Lepidoptera, Noctuidae). Adults were obtained from larval rearing on 12 food sources, six host-plants with a C3 photosynthetic metabolism and six host-plants with a C4 metabolism. Part of the adults obtained and the food source used during their immature development were lyophilized and macerated, and subjected to ?13C e ?15N isotopic analysis. The remaining adults of S. frugiperda were used to determine the composition of the gut microbiota by metagenomic analysis of the V1-V3 region of the 16S rRNA gene using a 454 sequencing platform. The carbon isotopic signatures obtained for the hostplants used as food source were between -31.37? and -25.07? for C3 plants, and - 13.03? and -12.26? for C4 plants. Adults of S. frugiperda obtained from larval rearing on C3 plants had a carbon isotopic signature between -30.36? and -23.72?, while those from C4 host-plants has between -18.25? and -13.28?. The metagenomic sequencing yielded 126,970 reads with an average of 421bp. The larval food source substantially influenced the diversity of the adult gut microbiota regardless of the plant\'s photosynthesis metabolism. Comparative analysis among gut microbiota in which the relative abundance was taken into account (weight- Unifrac) allowed the discrimination of the majority of the communities. Several OTUs were identified as exclusive to the adult gut microbiota from different food sources, but most of these OTUs were minor components of the community. OTUs 1199 and 2255, both exclusively associated with corn, were the only ones to represent at least 2.5% of their community.
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Lesueur, Didier. "Optimisation de la fixation d'azote dans la symbiose acacia mangium-bradyrhizobium : relations de la plante-hote et de la bacterie symbiote avec l'acidite et les oligoelements." Paris 6, 1992. http://www.theses.fr/1992PA066545.
Повний текст джерелаАнотація:
Le theme general de cette these est l'etude des relations ecophysiologiques entre la symbiose acacia mangium-bradyrhizobium et le milieu environnant. Ces recherches ont trois objectifs principaux: 1) determiner le role de certaines proprietes majeures des sols tropicaux telles que l'acidite et la presence excessive d'aluminium, dans l'ecologie des souches de bradyrhizobium, et dans le fonctionnement de la symbiose que forment ces bacteries avec differentes provenances de la plante-hote; 2) identifier les elements mineraux, particulierement les oligoelements, exiges par cette symbiose pour se former et fonctionner; 3) rechercher les mecanismes que la bacterie microsymbiote pourrait developper pour acquerir le ou les oligoelements indispensables a la symbiose. . .
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Rahoo, Ali Murad. "Studies on the Pesticidal Potential of Entomopathogenic nematodes, their bacterial symbionts and the toxins they produce." Thesis, University of Reading, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519862.
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Rodrigues, Pedro A. D. P., and Pedro A. D. P. Rodrigues. "Bacterial Symbionts at the Colony and Individual Levels: Integration through Behavior and Morphology in a Social Insect." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621295.
Повний текст джерелаАнотація:
The determination of a symbiotic association as beneficial requires good assessment of the costs and benefits involved in the maintenance and transmission of these microbes across generations. In social insects, symbiotic associations are complex as they may involve a network of interactions between individual and colony that result in stable associations over evolutionary time. My goal was to investigate the roles of behavior and morphology as integrators that have enabled the benefits of harboring gut microbes to reach both adult and growing brood in a colony. To achieve this goal, I used turtle ants (Cephalotes), a group that has co-evolved with their gut microbes since the Eocene (Sanders et al. 2014) and that shows a variety of morphological and behavioral specializations likely connected to this symbiotic association. In my dissertation I present evidence that the specialized behavior and morphology of Cephalotes are indeed strongly associated with mechanisms that ensure stability of ant-gut microbe interactions over evolutionary time. In Appendix A, I show that a valve between the crop and midgut (proventriculus) of C. rohweri works as a filtration organ, capable of excluding possible pathogens from the mostly liquid diet consumed by turtle ants. In addition, the proventricular filter is also associated with the structuring of the gut microbiota, dividing it in at least two great groups: one upstream and another downstream of the proventriculus. Through behavioral observation and microscopy, we also suggest that the formation of the proventricular filter is only complete after young and sterile workers (callows) are inoculated with the core group of symbiotic bacteria. In Appendix B, I present results confirming that the compartmentalization of gut microbiota is also present in the congener C. varians. I compare these results with previously published data, defining the meta-communities of the gut microbiota, and demonstrate that the previously recognized core microbiota is composed of compartment-specific microbial communities and lineages. This compartmentalization of the gut microbiota is similar to the one found in highly specialized herbivores, both vertebrates and invertebrates. In addition, I also sampled the infrabuccal pocket, a characteristic oral cavity found in ants and that has largely been ignored in studies of gut symbiosis. Based on my results, I provide compelling evidence that hindgut microbes are inoculated into food particles trapped in the infrabuccal pocket, aiding in digestion of this substrate. Moreover, I suggest that trophallaxis olays a central role in inoculation of food and individuals, and might be responsible for the transmission of nutrients that are predicted to result from the gut bacteria metabolism. Finally, in Appendix C I characterize abdominal trophallaxis in C. rohweri to gain insight on its role in the context of symbiotic associations with gut microbes. I show that the hindgut contents, including bacteria, can be transmitted via abdominal trophallaxis. This interaction is found to occur between all combinations of major and minor workers, in addition to callows. The rate of solicitation of abdominal trophallaxis is higher when individuals are protein starved, indicating that hindgut content may also be nutritive. Using shotgun metagenomic data, we show that the microbiota present in the infrabuccal pocket (mostly hindgut bacteria) are indeed capable of re-utilizing nitrogen and synthesizing essential amino acids, in addition to breaking down plant material. We also report that oral trophallaxis is a possible route for transmission of crop-specific bacteria for callows, as this group has performed oral trophallaxis at a relatively higher rate than older workers. Put together, these results highlight the importance of nestmate interactions and gut morphology in the establishment and maintenance of symbiotic microbes in a social insect, introducing a new model for explaining the evolution and functioning of ant-gut microbe symbiosis.
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Vala, Salvador Filipa De Freitas. "Genetic conflicts between cytoplasmic bacteria and their mite host." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2001. http://dare.uva.nl/document/59417.
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Conway, James G., and James G. Conway. "The Effects of the Symbiont Rickettsia on the Interactions Between a Whitefly Pest (Bemisia Tabaci) and a General Fungal Pathogen (Beauveria Bassiana)." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/626379.
Повний текст джерелаАнотація:
Some intracellular symbionts of insects confer host protection from a variety of bacterial, fungal and viral pathogens as well as from predators and parasitoids. Within the cryptic species complex of whiteflies known collectively as Bemisia tabaci is a cosmopolitan invasive agricultural pest, which is commonly infected with the symbiont Rickettsia sp. nr. bellii. Rickettsia swept rapidly through southwestern USA whitefly populations of the MEAM1 species and has been associated in a genotype-dependent manner with increased whitefly fitness and female biased sex ratios. Here we sought to determine whether Rickettsia in MEAM1 might have a defensive role against the general entomopathogenic fungus, Beauvaria bassiana. Nymphs from two lines of whitefly, each with Rickettsia positive (R+) and negative (R-) sublines were exposed to different doses of B. bassiana. The results provided evidence of protection by Rickettsia in one genetic line (MAC1) but not in the other (MAC2). In a third experiment, females of the four sublines were each outcrossed for two generations with males from an outbred whitefly culture, derived from the field within the year, and F2 nymphs from these four new sublines were exposed to the fungus. In this experiment, Rickettsia was protective in both MAC1-O and MAC2-O lines. Taken together, our results suggest the symbiont Rickettsia can confer protection against a generalist entomopathogenic fungus, B. bassiana, and that this protection is conditional on host genotype. To our knowledge, this is the first record of an insect symbiont conferring protection against a generalized and commercially available biological control agent. Bemisia tabaci MEAM1 is a global pest of warm temperate and tropical agriculture, and the prevalence of Rickettsia in many populations of this species could limit the predictability or efficacy of fungal pathogens as a potential management tool.
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Wentrup, Cécilia [Verfasser], Nicole [Akademischer Betreuer] Dubilier, and Monika [Akademischer Betreuer] Bright. "Acquisition and activity of bacterial symbionts in marine invertebrates / Cécilia Wentrup. Gutachter: Nicole Dubilier ; Monika Bright. Betreuer: Nicole Dubilier." Bremen : Staats- und Universitätsbibliothek Bremen, 2012. http://d-nb.info/1072046628/34.
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HAGNERE, CATHERINE. "Symbioses d'amibes libres et de bacteries de l'environnement hydrique induisant une mercuri-resistance et une limitation de la proliferation de bacteries pathogenes." Strasbourg 1, 1993. http://www.theses.fr/1993STR15011.
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Põlajev, Aleksei. "Selfish, mobile genes in honeybee gut bacteria." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-360510.
Повний текст джерелаАнотація:
Transposons are selfish, mobile genetic elements, moving within the genome. The transposase genemakes this possible, as it codes for the enzyme that catalyzes the movement. In the case of bacteria,they can also move horizontally between individual bacteria, and sometimes even between species.By default, they are a burden for the host organism, coding for a protein that the host does not need.They also pose the risk of disabling the host’s crucial genes by inserting themselves into it.Transposons are under some pressure to benefit the host, to help propagate themselves moreeffectively. And some transposons have indeed evolved to benefit the host. Lactobacillus kunkeei is a bacterial species known to reside in honeybee guts. It is known for itsrole in honey preservation and wine spoilage. The genome of L. kunkeei is reduced because it is asymbiont, however it contains an unusually high amount of transposons in its genome. In this study, the transposase genes (transposon enzymes) found in L. kunkeei are studied andcategorized. The L. kunkeei have been extracted from honeybees (Apis mellifera). The honeybeesthemselves have been collected from the islands Åland and Gotland. This study focuses on the transposase genes that come in pairs, one after another in the genome.Transposase genes were identified using annotation software and orthology-based methods. Theannotation software provides numbering for the genes, which allows finding paired genes. Thepaired genes were categorized based on alignments and phylogenetic software. Pseudogenizedtransposons were identified based on length and/or clustering into triplets. A total of 766 paired transposase genes were found. The transposase genes were found to take up1.9% of the genome, on average. A low level of diversity has been found when performingalignments and generating phylogenetic trees. The positions of the transposase genes are generallyconserved within phylogenetic groups. Pseudogenization has been detected for some transposasegenes – 4.5 per genome, on average. All of the studied transposons belong to the IS3 family, whichis a family of Class I transposons.
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Kaltenpoth, Martin. "Protective bacteria and attractive pheromones - symbiosis and chemical communication in beewolves (Philanthus spp., Hymenoptera, Crabronidae)." Doctoral thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=982568959.
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Schimak, Mario-Philip [Verfasser], Nicole [Akademischer Betreuer] Dubilier, and Monika [Akademischer Betreuer] Bright. "Transmission of bacterial symbionts in the gutless oligochaete Olavius algarvensis / Mario-Philip Schimak. Betreuer: Nicole Dubilier. Gutachter: Nicole Dubilier ; Monika Bright." Bremen : Staats- und Universitätsbibliothek Bremen, 2016. http://d-nb.info/1084866269/34.
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Nguyen, Van Phuong. "Plant and bacterial functions required for morphological bacteroid differentiation in the Aeschynomene-Bradyrhizobium model." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT158/document.
Повний текст джерелаАнотація:
Les légumineuses sont capables de développer des organes symbiotiques, les nodules, qui hébergent des bactéries du sol appelées rhizobia. Au sein des nodules les rhizobia intracellulaires se différencient en bactéroïdes capables de réduire l'azote atmosphérique en ammonium au bénéfice de la plante. En contrepartie, la plante alimente la bactérie en sources de carbone. Des études récentes sur le modèle symbiotique Medicago/Sinorhizobium ont montré dans les nodules la forte présence d'une grande diversité de peptides appelés NCR qui sont similaires aux peptides antimicrobiens (AMP) impliqués dans l'immunité innée. Ces NCR sont responsables du maintien de l'homéostasie entre les cellules hôtes et la forte population bactérienne qu'elles contiennent. Bien que certains NCR sont de vrais AMP, capable de tuer des bactéries in vitro, dans les nodules ils induisent plutôt une différenciation terminale caractérisée par une élongation cellulaire, une amplification du génome, une perméabilité membranaire et une perte des capacités de division de la bactérie. Néanmoins le mode d'action des NCR reste à élucider. Au cours de ma thèse j'ai participé à la caractérisation des processus de différenciation dans le modèle Aeschynomene, une légumineuse tropicale, Bradyrhizobium.Dans un premier temps, une nouvelle classe de NCR a été identifiée chez différentes espèces d'Aeschynomene. Ces NCR sont responsables de la différenciation des Bradyrhizobium via un processus similaire à celui décrit chez Medicago. Ces résultats suggèrent une évolution convergente des processus de différenciation chez les Dalbergioïdes (Aeschynomene) et le clade des IRLC (Medicago).Ensuite, pour identifier les fonctions bactériennes requises lors de la différenciation, j'ai criblé 53 mutants Tn5 d'Aeschynomene indica fix- . Huit gènes bactériens dont la mutation inhibe ou affecte le processus de différenciation ont été identifiés. Parmi eux, je me suis focalisé sur la DD-CPase une enzyme de modification du peptidoglycane et sur 2 gènes impliqués dans l'homéostasie du phosphate.La caractérisation du gène DD-CPase1 a permis de démontrer que le remodelage du peptidoglycane est requis pour une différenciation correcte des bactéroïdes chez les plantes hôtes qui produisent des NCR, en général, et chez Aeschynomene en particulier. Ces résultats suggèrent une interaction possible entre DD-CPase1 et des NCR conduisant à l'endoréplication des bactéroïdes.Enfin, j'ai étudié les propriétés physiologiques et symbiotiques des mutants pstC et pstB. Les mutants Tn5 des gènes pstC et pstB de la souche ORS285 de Bradyrhizobium sont sévèrement affectés par la carence en phosphate en culture pure et leurs propriétés symbiotiques (différenciation, réduction de l'azote) sont fortement réduites. Des analyses fonctionnelles plus approfondies de l'opéron Pst devraient permettre une meilleure compréhension du lien entre l'homéostasie du phosphate et l'efficience symbiotique dans l'interaction Aeschynomene-Bradyrhizobium.Mes travaux ont permis d'élargir nos connaissances sur l'évolution de la symbiose en montrant que le modus operandi impliquant des peptides dérivés de l'immunité innée utilisée par certaines légumineuses pour maintenir leur population bactérienne intracellulaire sous contrôle est plus répandue et ancienne qu'on ne le pensait et a été utilisée par l'évolution à plusieurs reprises. De plus différentes cibles bactériennes pouvant participer au processus de différenciation ont également été identifiéesThe legume species are able to form symbiotic organs, the nodules, that house soil bacteria called rhizobia. Within these nodules intracellular rhizobia differentiate into bacteroids, which are able to reduce atmospheric dinitrogen to ammonium for the benefit of the plants. In counterpart, the plants provide carbon sources to the bacteria. Recent studies on symbiotic model Medicago-Sinorhizobium showed that the nodules of M. truncatula produce a massive diversity of peptides called NCRs, which are similar to antimicrobial peptides (AMPs) of innate immune systems. These NCRs are responsible in maintaining the homeostasis between the host cells in the nodules and the large bacterial population they contain. Although many NCRs are genuine AMPs, which kill microbes in vitro, in nodule cells they do not kill the bacteria but induce them into the terminally differentiated bacteroids characterized by cell elongation, genome amplification, membrane permeability and loss of cell division capacity. However, the action mode of NCRs is still an open question. During my PhD thesis I focused on the identification of plant and bacterial functions required for bacteroid differentiation in the Aeschynomene-Bradyrhizobium model.Firstly, a new class of cysteine rich peptides (NCR-like) was identified in tropical aquatic legumes of the Aeschynomene genus, which belong to the Dalbergioid clade. These peptides govern terminal bacteroid differentiation of photosynthetic Bradyrhizobium spp. This mechanism is similar to the one previously described in Medicago suggesting that the endosymbiont differentiation in Dalbergioid and ILRC legumes is convergently evolved.Secondly, in order to identify the bacterial functions involved in bacteroid differentiation, I screened 53 fix- Tn5 mutants of the ORS278 strain on Aeschynomene indica. This screening allowed identify 8 bacterial genes, which inhibit or disorder the bacteroid differentiation. Among these identified genes, I focused on DD-CPase encoding a peptidoglycan-modifying enzyme and two genes pstC and pstB belonging to Pst-system.The characterization of DD-CPase gene demonstrated that the remodeling peptidoglycan enzyme, DD-CPase1, of Bradyrhizobium is required for normal bacteroid differentiation in host legumes that produce NCRs, in general, and in Aeschynomene spp., in particular. This prompts a possibility of direct interaction of DD-CPase1 with NCRs leading to endoreduplication of the bacteroids.Finally, I have investigated the physiological and symbiotic properties of different mutants of pstC and pstB genes. The Tn5 mutants of pstC and pstB genes of Bradyrhizobium sp. strain ORS278 severely affected symbiosis on A. indica and A. evenia. Further functional studies on pst-operon will provide deeper understanding the correlation between phosphate homeostasis and nitrogen fixation efficiency in Aeschynomene-Bradyrhizobium symbiosis.This study broadens our knowledge on the evolution of symbiosis by showing that the modus operandi involving peptides derived from innate immunity used by some legumes to keep their intracellular bacterial population under control is more widespread and ancient than previously thought and has been invented by evolution several times
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Paredes, Jorge R., and Jorge R. Paredes. "Phylogeography of the Asia Ii and the Americas Major Clades of the Bemisia Tabaci Sibling Species Group." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/626338.
Повний текст джерелаАнотація:
The Bemisia tabaci (Gennadius) sibling species group is known to comprise several morphologically undistinguishable mitotypes which can be separated into seven major phylogeographic clades using the 3' half of the mitochondrial cytochrome oxidase I gene. B. tabaci is the only vector of begomoviruses; it transmits the complex of viruses that cause the cotton leaf curl disease, which has rapidly spread from Pakistan to the Philippines, at southeast of Asia, in the last decade. The study of B. tabaci mitotypes has been limited to variants of worldwide distribution and those associated to agroecosystems, however, the study of indigenous mitotypes has been scarce. This dissertation provides a comprehensive study of the phylogeography and population biology of mitotypes belonging to two major phylogeographic clades, the Asia II and the Americas. The Asia II major clade contains the highest number of mitotypes, in contrast, there is a large gap in knowledge about mitotypes associated to highly endemistic niches in the Americas.
To study the population biology of mitotypes belonging to the Asia II major phylogeographic clade, two fragments of the mtCOI gene were amplified by polymerase chain reaction (PCR) for adult whiteflies sampled from mono and multi-cropping systems in the provinces of Punjab and Sindh in Pakistan. Phylogenetic analyses suggested that three indigenous mitotypes were distinctively distributed across ecosystems of Pakistan. The Asia II-5 and II-7 were found restricted to multi-cropping systems of Lahore, while the Asia II-1 was found widespread throughout the cotton growing region of Pakistan. Moreover, population analyses suggested the Asia II-1 is undergoing demographic expansion following a recent selective sweep or bottleneck. This event explains the predominance of Asia II-1 in Pakistan and its spread towards the southern province of Sindh. Additionally, differences in DNA polymorphism and diversity between mtCOI fragments derived in dissimilar evolutionary pairwise distances, suggestive of future implications in the “species” delimitation at a global scale when choosing one fragment over the other. The endosymbiotic bacteria assemblages associated to indigenous mitotypes Asia II-1, II-5 and II-7 were studied by analysis of 16S rRNA profiles. Besides the primary symbiont Portiera, Arsenophonus was detected almost fixed in the studied populations and several unique strains of Arsenophonus were detected in Asia II-5 and II-7, suggesting possible unique environmental adaptation capacities of these mitotypes. Hierarchical clustering of 16S rRNA profiles, proposed host-based and environmental-related differentiation. Additionally, the disruption of parallel cladogenesis between the primary symbiont and B. tabaci, disallows rejection of the hypothesis that gene flow among B. tabaci mitotypes occurs.
To study the population biology of indigenous mitotypes belonging to the Americas major clade, adult whiteflies were sampled from ecosystems of nine provinces in Ecuador. Based on phylogenetic analyses, three indigenous and one invasive mitotype were detected. Among the indigenous, a previously unrecognized mitotype, named ECU3, was found. Moreover, mitotypes were found coexisting in five locations, and the invasive B is thought to have displaced endemic mitotypes to the northern and eastern coastal habitats of Ecuador.
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Téfit, Mélisandre. "Drosophila melanogaster and its bacterial partners : community dynamics and effects on animal physiology." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEN055.
Повний текст джерелаАнотація:
Dans la nature, les relations symbiotiques sont très répandues, et d’une importance écologique fondamentale. Les animaux sont apparus, ont évolué et vivent maintenant constamment associés avec une multitude de micro-organismes. Parmi les différents types de symbioses existantes, celles liant le microbiote et son hôte occupent une place centrale et équilibrée, basée sur des relations commensales ou mutualistes entre les partenaires. Ce microbiote est de plus en plus étudié, notamment en raison du rôle crucial qu’il joue dans la santé animale ainsi que dans le développement de pathologies. Dans cette effort de recherche, Drosophila melanogaster représente un modèle de choix, grâce à la facilité de générer et maintenir des lignées de mouches axéniques, ainsi que de les réassocier avec une communauté microbienne définie.L’association de la drosophile avec l’un des ses commensaux naturels, Lactobacillus plantarum, a permis de révéler l’effet promoteur de croissance de cette bactérie. En cas de carence nutritionnelle, des larves associées avec L. plantarum se développent beaucoup plus rapidement que leurs semblables axéniques. L’ajustement du développement en fonction des conditions environnementales est cependant crucial pour la formation d’un individu à la santé optimale, et dans ce cas les individus grandissent plus vite alors que les conditions nutritionnelles sont pauvres. Nous avons donc cherché à déterminer si ce qui semble être un avantage au stade larvaire pouvait se révéler délétère pour les stades suivants et avoir un effet néfaste sur les mouches adultes. Nous avons montré que L. plantarum est bénéfique pour D. melanogaster tout au long du cycle de vie de la mouche et permet l’émergence précoce d’adultes matures et fertiles sans impact négatif sur leur santé et leurs performances. De plus, dans certaines conditions, cette souche commensale entraîne une augmentation de la durée de vie de mâles nutritionnellement carencés.Des études plus larges analysant l’interaction de la drosophile avec plusieurs espèces bactériennes peuvent informer sur la dynamique d’un microbiote de mouche. En effet, au sein de la niche environnementale, les bactéries sont échangées entre l’animal et son substrat nutritif, et ces transferts réciproques pourraient altérer la composition de la communauté. Nous avons étudié cette question en utilisant un microbiote naturel, et avons observé un haut degré de similitude entre les bactéries associées avec les mouches et la composition de la communauté bactérienne de la nourriture, illustrant le caractère stable de l’association du microbiote de la drosophile avec la population de mouches au sien de la niche.Ces résultats illustrent le pouvoir du modèle drosophile pour l’étude des interactions entre les animaux et leur microbiote, qui permet de déchiffrer la dynamique des communautés de bactéries commensales ainsi que leur impact sur la physiologie animaleIn nature, symbiotic relationships are widespread, and of paramount ecological importance. Animals have appeared, evolved, and are now living constantly associated with a variety of microorganisms. In the spectrum of different symbioses types, the microbiota occupies a central and balanced part by establishing commensalistic or mutualistic relationships with its host. Over the last years, the microbiota has been extensively studied given the crucial role it plays in animal health and disease. In this research effort, Drosophila melanogaster represents a fruitful model, thanks to the ease to generate and maintain axenic flies, and the simplicity of re-associating them with a defined microbial community.The association of Drosophila with one of its natural commensals, Lactobacillus plantarum, revealed a growth-promoting effect mediated by this bacterial species. In case of nutrient scarcity, larvae associated with L. plantarum develop twice faster than the germ-free ones. However, adjusting development to environmental cues is key to organismal fitness, and yet here animals are growing fast even though the nutritional conditions are poor. We thus questioned whether what seems like an advantage could in turn be deleterious at later stages, and adversely impact adult fitness. We showed that L. plantarum is a true beneficial partner for D. melanogaster throughout the fly life cycle. Indeed, it allows the precocious emergence of mature and fertile adults without fitness drawbacks, and in certain conditions, this commensal can even increase the lifespan of nutritionally challenged males.Broader studies assessing the interaction of Drosophila with several bacterial species can inform about the dynamics of a fly microbiota. Indeed, in the environmental niche bacteria are transferred between the fly and its nutritive substrate, and these reciprocal transfers could alter the composition of the community. We addressed this question using a wild-derived microbial community and observed a high degree of similarity between the bacteria associated with the flies and the composition of the community in the diet, illustrating the stable association of the Drosophila microbiota with the fly population in the niche.Altogether these results emphasize the power of the Drosophila model in the study of the relationships between animals and their microbiota, which allows deciphering the dynamics of commensal bacterial communities and their impact on animal physiology
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Weglarz, Kathryn M. "Investigating the Roles of Bacterial Endosymbionts in the Evolution of Adelgidae (Hemiptera: Sternorrhyncha)." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7645.
Повний текст джерелаАнотація:
Insects form close partnerships, or symbioses, with bacteria. These partnerships allow the insects to use resources that would be unavailable to them otherwise. Certain insects, hemipterans, are able to feed on nutrient-poor plant-sap because these bacteria supplement their diets. While this association is beneficial for both the insect and bacteria, it also comes with consequences: the genomes of bacterial symbionts typically undergo extreme degradation, becoming small and lacking many genes necessary for typical bacterial functioning. In the Hemiptera, aphids, mealybugs, cicadas, true bugs,and their relatives, these bacterial partnerships tend to be stable over millions of years. However, adelgids (Aphidoidea: Adelgidae) are highly unusual in that their symbiotic bacteria have been frequently replaced. These replacements offer a unique opportunity to explore the effects of symbiont role and age on symbiont genome degradation. My dissertation uses the pattern of adelgid symbiont gains and losses to understand the process of symbiont replacements and co-symbiont gain. I accomplished this by sequencing and annotating the genomes of adelgid symbionts from across the family, first focusing on the symbionts from a pest species, then expanding to representatives from across the family, and finally conducting an in-depth exploration of how the genomes of a symbiont found in two branches of the adelgids varies between species. Through this work I demonstrate that adelgid symbionts are nutritional providers, they have a unique pattern for distributing the work of providing nutrients between the symbiont pairs, and that a symbiont’s precedence, whether it was there first or whether it joined another symbiont, has an impact on genome degradation.
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Zheng, Hao [Verfasser], and Andreas [Akademischer Betreuer] Brune. "Genome Evolution of Endomicrobia: From Free-Living Bacteria to Intracellular Symbionts of Termite Gut Flagellates / Hao Zheng. Betreuer: Andreas Brune." Marburg : Philipps-Universität Marburg, 2015. http://d-nb.info/1080299211/34.
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Negandhi, Karita L. "Microbial Communities with Emphasis on Coral Disease-Associated Bacteria within Florida Reef Sponges." NSUWorks, 2009. http://nsuworks.nova.edu/occ_stuetd/109.
Повний текст джерелаАнотація:
Previous studies have shown that bacteria associated with coral diseases are not found in the surrounding water column at detectable levels, yet at the same time, coral diseases are becoming more prominent. Sponges are coral reef residents, which expel filtered seawater that is practically sterile of microbes. Therefore sponges harbor very diverse and abundant microbial communities. This leads to the possibility that coral disease associated bacteria (CDAB) may be present within reef sponge microcosms. In order to identify internal microbes, nonculturable techniques including fluorescent in situ hybridization (FISH), electron microscopy (EM) and 16S small subunit (SSU) rRNA gene cloning and sequencing were applied to local Florida reef sponges Agelas tubulata, Amphimedon compressa and Aplysina fistularis. This study targeted potential coral bacterial pathogens with FISH including Aurantimonas coralicida, Cytophaga sp., Desulfvibrio spp., Firmicutes, Serrattia marcescans, and Vibrio shiloni AK-1. All of the targeted coral disease associated bacteria were found within A. compressa and A. tubulata with FISH, but not in every individual. Differences in the spatial arrangement of targeted microbes were also seen within these sponge hosts. For instance, the two anaerobic bacteria Desulfovibrio spp. and S. marcescans were found in aggragates. In addition, electron microscopy revealed a higher abundance of bacteria in Applysina fistularis choanosome compared to the ectosome.
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Saidin, Jasnizat Bin. "Isolation and characterization of Suberites domuncula (Olivi, 1792) associated bacteria : insights on potential molecules of communication." Lorient, 2012. http://www.theses.fr/2012LORIS269.
Повний текст джерелаАнотація:
Cinquante et une bactéries cultivables ont été isolées d partir de l'éponge Suberifes domuncula Récoltee en Bretagne (France). Celles-ci se repartissent entre les Gammaproteobacteria (é3%), les Firmicutes (18%), les Alphaproteobacteria (12o/o) et les Bacteroides (7%). La production d'homosérines lactones (HSL) a été recherchée chez 115 de ces isolats bactériens en utilisant un test, en microplaque, d'induction de la luminescence d'une souche d'Escherichia colipSB40é. Les surnageants de culture a 24, 48,72 et 9éh contenant potentiellement des HSL ont été testés. Des valeurs positives d'induction (des AHL Ont été produites) ainsi que des valeurs négatives ont été obtenues. Des expériences complémentaires ont Montre que pour ces dernières, les inhibitions de la luminescence étaient dues à un effet bactériostatique/bactéricide. Soixante quinze bactéries produisirent des HSL au moins une fois au cours D’une phase de leur culture. Dix neuf bactéries isolées ont produit des AHL tout au long de leur culture, i. E. De 24 d 9é heures ; 52 d'entre-elles présentaient des effets mixtes (favorisant et inhibant la production de Luminescence), 30 une inhibition et 4 n'ont présenté aucune activité. La production d'HL estimée au court De la croissance, était d 24, 48,72 et 9é heures respectivement de 22,31o/o, 42,31o/o 3é,47% 35,30%. La production de composés inhibant la luminescence de la souche E. Coli pSB40é était quant A elle, d ces mémes temps de culture, de 47,é90/o, 27,é9Yo, 47,01Yo et 55,29o/o. Parmi les producteurs d'HSL (au moins une fois au cours de la culture), 4é des 75 isolats (é8%) étaient des Gammaproteobacteria,9 (13%) des Alphaproteobacteria, T (10%) des Firmicutes et é (9%) des Flavobacteriia. Les producteurs d'HSL au sein de la famille des Gammaproteobacteria se répartissaient entre Pseudoalteromonas (15), Shewanella (7), Endozoicomonas et Coweillia (é), Vibrio (5), Pseudomonas (4) el Microbulbifer el Cobetia (1). Pour les Alphaproteobacteria un genre contenait 9 espdces : celui des Pseudovibrio. Le groupe des Flavobacteriia contenait le genre Tenacibaculum avec cinq espdces et le genre Flavobacterium une seule espdce. Sept inducteurs de luminescence d'E. Coli pSB40é étaient des Firmicutes. Dans cette étude, dix espdces bactériennes ont été repérées comme probablement endemiques de l'éponge S. Domuncula relative d la zone de l'étude. Les plus proches des bactéries apparentées d ce groupe serait une bactérie non cultivable, le clone Past-O03, provenant d'un corail (Porites asfreiodes) avec lequel elle présente 93-9é% d'identite. Le représentant cultivable le plus proche serait I'espdce Endozoicomonas elysicola MKT110 isolee dr partir d'un nudibranche, Elysia ornata (91 -93%). L'analyse phylogénétique Complémentaire des séquences disponibles d partir de NCBI a révélé que la bactérie provenant de S. Domuncula etait plus liée au groupe de la bactérie non cultivable avec une valeur de bootstrap de 85% qu'd celui du groupe des Endozoicomonas (valeur de bootstrap de é0%). Ce travail est le premier d signaler que la famille Endozoicomonas serait en mesure de produire des HSL. En effet, parmi les cinq isolats testés, I'un d'entre eux, Endozoicomonas sp. Cdtt2, a démontré une production d'HSL pendant toute la phase de croissance, soit pendant les 9é heures de culture. L'espdce Endozoicomonas sp. Hex311 produirait quant d elle un (des) compose(s) inhibiteur(s) tout au long de sa culture. Les trois autres isolats démontrent une inhibition de la luminescence de la souche E. Coli raportrice tout au long de leur croissance. Néanmoins la possibilite que des HSL soient également produites ne peut étre negligee. Par ailleurs, dans cette étude, deux bactéries ont été sélectionnées pour isoler des composés actifs présents dans les surnageants de culture: Pseudoalteromonas sp. Hex322 el Pseudomonas sp. H312. Pseudoalteromonas sp Hex322 montrait un effet inhibiteur de la luminescence d'E. Coli pSB40é. L'etude des fractions de son surnageant a montré que le(s) compose(s) inhibiteur (s) etait(ent) présents dans les fractions non-polaires alors que les fractions polaires présentaient un effet anti-biofilm. Malheureusement, en raison des quantités infimes récoltées de fractions non-polaires et polaires avec une caractéristique trds polaire, aucun composé actif n'a eté isolé. Quant d Pseudomonas sp. H312, trois composés purs ont été isolées : I'acide phénazine-1-carboxylique, un di-rhamnolipide C10-C10 et des glycolipides. Les expériences que nous avons menées en mettant en contact ces deux bactéries ont montré qu'elles seraient compétitrices I'une de l'autre. Mais, des expériences complémentaires seront nécessaires pour conclure sur ce pointOne hundred and fifty one cultivable bacteria were isolated from the sponge Suberifes domuncula collected in Brittany (France). This bacterial population consisted of Gammaproteobacteria (é20/0), Firmicutes (18Yo), Alphaproteobacteria (13%) and Bacteroides (7%). One hundred and fifteen were subjected to a microplate luminescence assay using E. Coli pSB40é as a reporter strain in order to determine a production of AHLs, using the supernatants at 24, 48,72 and 9é hours. These molecules are a possible mean to communicate between resident bacteria and/or the host. Both positive luminescence values as well as negative ones were obtained. After further experimentations, the negative values were the result of bacteriostatic/bactericidal effects. Among the AHLs producers 75 did not produce these molecules constantly but, at least once, during the time of the culture. Only 19 of them produced AHLs throughouttheir growth (from24 to 9é hours). Fifty two bacteria exhibited both effects (enhancement and inhibition of the luminescence), 3é showed a inhibition effect and 4 had no activity. Ln term of AHLs the productions at specific growth's time, at 24 hours of growth only 22. 31o/o of them were able to produced AHL, while at the 48 hours growth, the number of isolates that produced AHL were 42. 31o/o, then at 72 and 9é hours, the percentage of the AHL producers were 3é. 47o/o and 35. 30%, respectively. As for the production of E. Coll inhibitor compound(s) at specific growth time was 47. é9% at 24 hours of growth, 27. é9Yo at 48 hours, 47. 01% at 72 hours and 55. 29% at 9é hours. Among the AHL producers (at least once throughout the culture time), 4é out of 75 isolates (é8%) were Gammaproteobacteria, 9 (13Yo) were Alphaproteobacteria,7 (10o/o) were Firmicufes and é (9%) were Flavobacteriia. The AHLs producers within the Gammaproteobacteria were those from the genera Pseudoalteromonas (15 bacteria), Shewanella (7), Endozoicomonas (é) and Coweillia (é), Vlbrio (5), Pseudomonas (4), Microbulbifer (1) and Cobetia (1). The Alphaproteobacteria contained only one genus: Pseudovibrio with nine isolates. Fhe Flavobacteriia group contained the genus Tenacibaculum with five isolates and one from the genus F/avobacterium. Seven inducing the luminescence were from the Phylum Firmicutes. Ln this study ten isolates probably belonged to a sponge-specialist bacterial symbiont group endemic to S. Domuncula collected from the area of the study. Lndeed, the closest related bacterium for this group was an Uncultured bacterium, clone Past-O03, coming from a coral (Porites asfreiodes) (93-9é% of identity) while the closest cultivable representative was Endozoicomonas elysicola MKT110 isolated from the sea slug, Elysia ornata (91-93%). Further phylogenetic analysis of the available sequences from NCBI revealed that this group was more related to the group of the uncultured bacterium with a bootstrap value of 85% rather than to lhe Endozoicomonas group (bootstrap value: é0%). Besides, we reported for the first time, the capability of lhe Endozoicomonas family to induce luminescence relative to the production of AHLs. Among five sponge- Endozoicomonas tested, one of lhem, Endozoicomonas sp. Cdtt2, showed a possibility of AHLs production throughoutthe 9éh of culture. An other Endozoicomonas, Hex311 as for it, produced an inhibitor compound(s) al24 hours; then, from 48 to 9é hours AHLs were produced. The other three Endozoicononas displayed an inhibition of the E. Coli luminescence reporter strain throughout their growth. Nevertheless the possibility of an AHLs production cannot be neglected this one being hidden. For other studies, we selected two sponge-associated bacteria to proceed to the isolation of active compounds from their culture supernatants: Pseudoalteromonas sp. Hex322 and Pseudomonas sp. H312. The Pseudoalteromonas sp. Hex322 was choosen because it inhibited the luminescence of the E. Coli reporter strain so, produced a bacteriostatic/bactericidal compound(s). Further investigations of the fractions showed that the inhibitor compound(s) was present in the non-polar fractions while the polar fractions exhibited an anti-biofilm effect. Unfortunately, due to the minute quantity of the non-polar and polar fractions with a very polar characteristic, none of the active compounds were successfully isolated. Concerning Pseudomonas sp. H312, three pure compounds were isolated: the phenazine-1-carboxylic acid, a dirhamnolipid Cro-Cro and a glycolipid. The experiments setting in contact both bacteria showed that they seemed to be in competition, but to gain conclusive insights more experiments are needed
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Dittmer, Jessica. "Diversity of endosymbiotic bacterial communities in terrestrial isopods : the role of feminizing Wolbachia and other major players." Thesis, Poitiers, 2013. http://www.theses.fr/2013POIT2322/document.
Повний текст джерелаАнотація:
Les interactions isopodes terrestres-Wolbachia féminisantes constituent un excellent modèle d'étude des interactions multipartites complexes. A ce jour, trois Wolbachia féminisantes, issues d'histoires évolutives différentes, ont été identifiées chez l'hôte Armadillidium vulgare. L'objectif de cette thèse est d'avoir une vue plus complète du microbiote d'A. vulgare et de l'impact des souches de Wolbachia sur cette communauté bactérienne. Dans ce but, des approches quantitative et métagénomique ont été combinées afin de caractériser le microbiote d'A.vulgare à plusieurs niveaux d'intégration: (i) dans des populations naturelles et des lignées contrôlées de laboratoire, (ii) au sein de différents tissus hôtes et (iii) en relation avec le statut d'infection par Wolbachia. Aucun microbiote coeur n'a été mis en évidence malgré une relative homogénéité des communautés symbiotiques dans les tissus de l'hôte. De plus, les bactéries environnementales avaient un impact important sur le microbiote symbiotique. Chez les animaux infectés, Wolbachia représente la bactérie dominante et le facteur majeur de la structuration de la communauté symbiotique. Nous avons également mis en évidence la présence d'un autre constituant majeur du microbiote dans tous les tissus de l'hôte: Candidatus Hepatoplasma crinochetorum, un symbiote facultatif réputé jusque-là pour être seulement associé aux glandes digestives de l'intestin. Afin d'éclairer les interactions potentielles entre hôte et ce symbiote relativement peu connu, la séquence du génome de Ca. H. crinochetorum a été obtenue. Une analyse préliminaire des interactions fonctionnelles des voies métaboliques impliquées dans la digestion de la cellulose nous a permis d'identifier des enzymes cellulolytiques spécifiques de l'hôte et du symbiote. Cette étude ouvre de nouvelles perspectives dans l'étude de la symbiose chez les isopodesIn recent years, there has been a shift of focus in symbiosis studies, away from the traditional 'one host-one symbiont' concept towards a more holistic, community-based approach. This concept takes into account that a host is not only associated with one bacterium, but harbours and interacts with a diverse bacterial community, the microbiome. Terrestrial isopods represent an excellent model system for the understanding of complex multipartite symbioses due to their well-characterised association with feminizing Wolbachia bacteria. To date, three different feminizing Wolbachia strains have been identified in Armadillidium vulgare, presumably representing different host-symbiont co-evolutionary histories. The aim of this PhD was to get a more complete picture of the terrestrial isopod microbiome and the role of Wolbachia within the bacterial community. In order to achieve this, quantitative and metagenomic techniques were combined to characterize the microbiome of A. vulgare on multiple levels: (i) Field vs. lab populations, (ii) in different host tissues, and (iii) in relation to Wolbachia infection status, i.e. presence/absence of Wolbachia as well as infection with different Wolbachia strains. Wolbachia represented the predominant member of the bacterial community in infected individuals and was identified as an important factor influencing bacterial community structure. Apart from Wolbachia, we detected a second highly abundant bacterium: Candidatus Hepatoplasma crinochetorum, a facultative symbiont previously reported from the midgut caeca, was for the first time observed in all tested host tissues. The potential interactions of Wolbachia and Ca. H. crinochetorum constitute an interesting example for symbiont-symbiont relationships between two highly abundant members of a diverse bacterial community
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Ali, Sajjad [Verfasser], Stefan [Akademischer Betreuer] Vidal, Petr [Akademischer Betreuer] Karlovsky, and Stefan [Akademischer Betreuer] Schütz. "Exploring the interactions of bacterial secondary symbionts (BSS) in wheat aphids, Sitobion avenae F. with parasitoids / Sajjad Ali. Betreuer: Stefan Vidal. Gutachter: Petr Karlovsky ; Stefan Schütz." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://d-nb.info/1079384561/34.
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Souza, Danilo Tosta. "Exploração da diversidade bacteriana de esponjas marinhas por abordagens dependente e independente de cultivo." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11138/tde-06012017-113512/.
Повний текст джерелаАнотація:
Este estudo descreve a diversidade e composição das comunidades bacterianas associadas a cinco esponjas marinhas, e o potencial destes microrganismos como produtores de substâncias bioativas com propriedades fungicidas. As esponjas vivem em simbiose com microrganismos que apresentam alto interesse ecológico, evolutivo e biotecnológico. Contudo, este sistema microbiano permanece pobremente entendido. Para totalmente compreender a biologia desses animais é necessário descrever os fatores ecológicos e evolutivos influenciando a estrutura e dinâmica de sua microbiota. Nesta tese é defendida a hipótese de que a composição taxonômica e estrutura das comunidades bacterianas se correlaciona com o parentesco filogenético de seus hospedeiros. Neste trabalho, as comunidades bacterianas associadas às esponjas Aplysina fulva, Aiolochroia crassa, Chondrosia collectrix, Didiscus oxeata e Scopalina ruetzleri foram examinadas usando a plataforma Ion torrent para sequenciamento parcial do gene 16S rRNA. A água do mar circundante aos espécimes foram coletadas para comparações com a microbiota de esponjas. As análises detectaram um complexo e específico sistema microbiano vivendo em esponjas, com as unidades taxonômicas operacionais dominantes classificadas nos filos: Acidobacteria, Actinobacteria, Chloroflexi, Proteobacteria e Gemmatimonadetes. Apesar da ocorrência simpátrica dos espécimes, as comunidades bacterianas diferiram significativamente entre as espécies de esponjas e a água do mar. Contudo, foi observado que as comunidades bacterianas habitando esponjas filogeneticamente mais próximas (A. fulva e A. crassa) são mais similares uma para com a outra, do que quando comparado com as comunidades em um táxon mais distante filogenitacamente (C. collectrix). O isolamento de bactérias foi realizado nas esponjas D. oxeata e S. ruetzleri. Cinquenta e seis linhagens foram isoladas e classificadas em três filos: Actinobacteria, Proteobacteria e Firmicutes. As análises filogenéticas indicaram cinco possíveis novas espécies bacterianas. Com base na taxonomia polifásica, um dos isolados, denominado ASPSP 40, foi caracterizado como pertencente a uma nova espécie do gênero Saccharopolyspora, para qual o nome Saccharopolyspora spongiae sp. nov. foi proposto. Dois isolados bacterianos demonstraram forte atividade antagônica contra as seguintes espécies de Pythium: P. aphanidermatum, P. graminicola e P. ultimum. Os metabólitos secundários desses isolados, assim identificados como pertencentes aos gêneros Terrabacter sp. ASPSP 140 e Bacillus sp. ASPSP 434, foram identificados por LC-MS/MS como sendo uma mistura de dipepitídeos cíclicos pertencentes à classe das dicetopiperazinas (DKP). Este é o primeiro relato da atividade fungicida e, consequentemente, a detecção de DKP a partir do gênero Terrabacter.This study describes the diversity of associated bacterial communities to five marine sponges, and the potential of these microorganisms as producers of bioactive substances with fungicidal properties. Sponges live in symbiosis with microorganisms that have a high ecological interest, evolutionary and biotechnological. However, this microbial system remains poorly understood. To fully understand sponge biology, it is necessary to describe the ecological and evolutionary factors that influence the structure and dynamics of their microbial communities. In this work, it is supported the hypothesis that the taxonomic composition and structure of bacterial communities correlate with phylogenetic relatedness of their corresponding hosts. Bacterial communities associated with the sponges Aplysina fulva, Aiolochroia crassa, Chondrosia collectrix, Didiscus oxeata and Scopalina ruetzleri were examined using the Ion Torrent platform for partial sequencing of the 16S rRNA gene. Seawater surrounding specimens were collected for comparisons. The analysis detected a complex and specific microbial system living in sponges, with the operational taxonomic units dominant classified in the phyla: Acidobacteria, Actinobacteria, Chloroflexi, Proteobacteria and Gemmatimonadetes. Despite sympatric occurrence of the specimens, the studied sponges presented different bacterial compositions that differed from those observed in seawater. However, lower dissimilarities in bacterial communities were clearly observed within sponges from the same phylogenetic group (A. fulva and A. crassa). Isolation of bacteria was done from the sponges D. oxeata and S. ruetzleri. Fifty-six strains were isolated and classified into three phyla: Actinobacteria, Proteobacteria and Firmicutes. Phylogenetic analysis indicated five possible novel bacterial species. Based in a polyphasic taxonomy approach, one of the isolates denominated ASPSP 40 was identified as belonging to a novel species of the genus Saccharopolyspora for which the name, Saccharopolyspora spongiae sp. nov. has been proposed. All bacterial isolates were evaluated by their antagonisms against Pythium species. Two of them, Terrabacter sp. ASPSP 140 and Bacillus sp. ASPSP 434 demonstrated strong potential in inhibiting the following species P. aphanidermatum, P. ultimum and P. graminicola. The bioactive secondary metabolites of both, characterized by LC-MS/MS, were identified as a mixture of cyclic dipepitides belonging to the class of diketopiperazine (DKP). This is the first report of fungicidal activity, and thus the detection of DKP of the genus Terrabacter.
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LEITE, Jakson. "Simbiose feij?o-caupi e riz?bio: diversidade de bact?rias associadas aos n?dulos." Universidade Federal Rural do Rio de Janeiro, 2015. https://tede.ufrrj.br/jspui/handle/jspui/1992.
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Cowpea [Vigna unguiculata (L.) Walp] is an important crop in northeastern Brazil with strategic advantages for production in semi-arid region, such its drought tolerance and good performance in low fertility soils. In addition, the nitrogen (N) fixed in symbiosis with rhizobia eliminates the demand for N fertilizers, with economic, social and environmental benefits. Little is known about the genetic diversity of bacteria associated to cowpea nodules in Brazilian semi-arid. The aim of the study was to characterize the bacterial diversity of Brazilian semi-arid soils associated with nodules of different cowpea cultivars by dependent and independent bacterial cultivation strategy. Initially a collection of 86 bacteria cowpea nodules isolated from semiarid soils was genetically characterized by partial 16S rRNA gene sequencing and symbiotic genes nifH and nodC. The sequences were compared with the NCBI database to identify isolates and phylogenetic relationships were built. In another study, we applied the independent cultivation method to evaluate bacterial communities associated with the nodules of two cowpea cultivars (BRS and BRS Acau? Pujante), in Ultisol with no history of cowpea cultivation. Nodules (N) were collected 35 days after germination, and soil samples (BS) from 0-20 cm deeper. DNA was extracted for analysis of bacterial communities with 454 pyrosequencing of the 16S ribosomal gene rRNA. The analysis of the diversity of the bacterial collection of the nodules 54 of the 86 isolates were Bradyrhizobium. Other (32) belong to Rhizobium (13) and Microvirga (1), Alfaproteobact?ria class; Burkholderia (8), and Ralstonia (1), Betaproteobacteria class; Acinetobacter (1), Cronobacter (3), Enterobacter (1), and Pantoea (1), Gamaproteobact?ria; and Leifsonia (3), phylum Actinobacteria. As Bradyrhizobium predominated, analyzes were performed with the almost full 16S rRNA, nifH and nodC and isolates were distributed in 5 lines: 16S rRNA type I (44 isolates), type II (6), Type III (1), Type IV ( 2) and type IV (1). Phylogenetic analysis of the 16S rRNA gene grouped the Type I strain in the large group Bradyrhizobium japonicum and close to the type strain of Bradyrhizobium yuanmingense. The analyses of the nifH and nodC gene separated the isolates in 5 symbiotic lines (I, II, III, IV and IV) and were congruent among them, which supports the theory of monophyletic in origin symbiotic gene Bradyhrizobium. The symbiotic lineages I and II are nearby and correspond to all isolates with 16S rRNA type I, being the dominant group associated with nodules. The partial 16S rRNA gene sequencing of bacterial communities showed high diversity in the three environments (BS, RS and N). The communities associated with the nodes were significantly different (p> 0.01) from the surrounding nodules (LS and RS). Phyla Actinobacteria, Bacteriodetes, Proteobacteria were plentiful for BS and RS. In nodes, the Proteobacteria and Bacteriodetes phyla predominated, Gammaproteobacteria being (58.8%) and Alphaproteobacteria (37.4%) in the phylum Proteobacteria and dominant Flavobacteriia (84.8%) and Sphingobacteriia (10.9%) in the phylum Bacteriodetes. For gender, Chryseobacterium, Entreobacter and Bradyrhizobium dominate in all nodes samples where Chryseobacterium prevailed in BRS Acau? and Enterobacter in BRS Pujante.
O feij?o-caupi [Vigna unguiculata (L.) Walp] ? uma das principais culturas no Nordeste do Brasil com vantagens estrat?gicas para produ??o no semi?rido, como toler?ncia a seca e bom desempenho em solos de baixa fertilidade. Al?m disso, fixa N em simbiose com riz?bios eliminando a demanda de fertilizantes nitrogenados, com benef?cios econ?micos, sociais e ambientais. Pouco se sabe sobre a diversidade gen?tica de bact?rias associadas aos n?dulos de feij?o-caupi no semi?rido. O objetivo do estudo foi caracterizar a diversidade de bact?rias de solos do semi?rido brasileiro associadas aos n?dulos de diferentes cultivares de feij?o-caupi com arbordagem que depende e independe de cultivo das bact?rias. Inicialmente uma cole??o de 86 bact?rias de n?dulos de feij?o-caupi isoladas de solos do semi?rido foi caracterizada geneticamente pelo sequenciamento parcial do gene 16S rRNA e dos genes simbi?ticos nifH e nodC. As sequ?ncias foram comparadas com as do banco de dados do NCBI para identificar os isolados e as rela??es filogen?ticas dos mesmos com as de esp?cies conhecidas. Em outro estudo, aplicou-se o m?todo independente de cultivo para avaliar comunidades de bact?rias associadas aos n?dulos de dois cultivares de feij?o-caupi (BRS Pujante e BRS Acau?), em Argissolo Amarelo sem hist?rico de uso com a lavoura. Os n?dulos (N) foram coletados 35 dias ap?s a germina??o e a amostragem do solo (BS) de 0-20 cm. O DNA das amostras foi extra?do para an?lises das comunidades bacterianas com 454 pirosequenciamento do gene ribossomal 16S rRNA. Na an?lise da diversidade da cole??o de n?dulos 54 dos 86 dos isolados foram de Bradyrhizobium. Os demais (32) pertencem aos g?neros Rhizobium (13) e Microvirga (1), classe Alfaproteobact?ria; Burkholderia (8) e Ralstonia (1), classe Betaproteobact?ria; Acinetobacter (1), Cronobacter (3), Enterobacter (1) e Pantoea (1), Gamaproteobact?ria; e Leifsonia (3), filo Actinobact?ria. Como Bradyrhizobium predominou, foram feitas an?lises com os genes 16S rRNA, nifH e nodC e os isolados distribu?ram-se em 5 linhagens: 16S rRNA tipo I (44 isolados), tipo II (6), tipo III (1), tipo IV (2) e tipo IV (1). A an?lise filogen?tica do gene 16S rRNA agrupou a linhagem tipo I no grande grupo Bradyrhizobium japonicum e pr?ximo da estirpe tipo de Bradyrhizobium yuanmingense. A an?lise dos genes nifH e nodC separou os isolados em 5 linhagens simbi?ticas (I, II, III, IV e IV) e as ?rvores foram congruentes, o que suporta a teoria da origem monofil?tica de genes simbi?ticos em Bradyhrizobium. As linhagens simbi?ticas I e II s?o pr?ximas e correspondem a todos os isolados com 16S rRNA tipo I, sendo o grupo dominante associado aos nodulos. O sequenciamento parcial do gene 16S rRNA das comunidades bacterianas mostrou alta diversidade nos tr?s ambientes (BS, RS e N). As comunidades associadas aos n?dulos foram significativamente diferentes (p> 0,01) das que cercam os n?dulos (LS e RS). Os filos Actinobacteria, Bacteriodetes, Proteobacteria foram abundantes para BS e RS. Em n?dulos, os filos Proteobacteria e Bacteriodetes predominaram, sendo Gammaproteobacteria (58,8%) e Alphaproteobacteria (37,4%) dominantes no filo Proteobacteria e Flavobacteriia (84,8%) e Sphingobacteriia (10,9%) no filo Bacteriodetes. Para g?nero, Chryseobacterium, Entreobacter e Bradyrhizobium dominam em todas as amostras de n?dulos, onde Chryseobacterium predominou em BRS Acau? e Enterobacter em BRS Pujante.
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Miquel-Guennoc, Cora. "Étude de l’interaction physique entre le champignon ectomycorhizien Laccaria bicolor S238N et la bactérie auxiliaire de la mycorhization Pseudomonas fluorescens BBc6." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0028/document.
Повний текст джерелаАнотація:
Dans les sols, les champignons ectomycorhiziens (ECM) forment une symbiose très répandue avec les racines des arbres et contribuent ainsi à leur croissance et à leur santé. Des études antérieures ont montré que certaines bactéries pouvaient influencer positivement la symbiose entre les ECM et les arbres, appelées BAM pour Bactéries Auxiliaires de la Mycorhization. Les mécanismes de l’effet auxiliaire des BAM sont encore peu connus. En amont de cette thèse, il avait été montré in vitro que la BAM Pseudomonas fluorescens BBc6 formait des structures similaires à des biofilms sur les hyphes de l'ECM Laccaria bicolor. Dans ce contexte, afin d'enrichir les connaissances concernant les interactions entre les ECM et les BAM, cette thèse a porté sur l'interaction physique entre ces deux organismes. L'étude a en partie été réalisée via une méthode d'analyse par microscopie confocale, développée durant cette thèse. Les résultats obtenus ont montré que cette bactérie formait des biofilms localisés préférentiellement sur la région apicale des colonies de l'ECM ce qui pourrait indiquer une interaction trophique. L'existence d'une telle interaction a d'ailleurs par la suite été confirmée. Les résultats ont également montré que l'interaction physique entre Laccaria bicolor et BBc6 n'est pas spécifique puisque l'ensemble des treize autres souches bactériennes testées a formé des biofilms sur les hyphes de Laccaria bicolor. En revanche, BBc6 s'est montrée incapable de former des biofilms sur certains champignons appartenant aux Ascomycètes, suggérant des mécanismes d'inhibition. De plus, l'étude de la matrice des biofilms formés par BBc6 a révélé la présence de réseaux de filaments constitués d'ADN qui semblent structurer ces biofilms et qui ont aussi été observés chez l'ensemble des souches bactériennes testées. Ces résultats révèlent un rôle structural de la molécule d'ADN qui, bien qu'il semble répandu, n'a que peu été reporté jusqu'à présent. Enfin, il a été montré que des mutants de BBc6 qui ont perdu leur effet auxiliaire forment des biofilms différents de la souche sauvage sur une surface abiotique suggérant un lien potentiel entre l'effet auxiliaire et la formation de biofilmsIn soil ecosystems, ectomycorrhizal fungi (ECM) form a widespread symbiosis with roots of trees, contributing to tree growth and health. It has been shown that some bacteria, called mycorrhization helper bacteria (MHB), stimulate mycorrhizal symbiosis. The mechanisms of this helper effect are poorly understood. Previous studies have shown that the MHB Pseudomonas fluorescens BBc6 formed biofilm-like structures around the hyphae of the ECM Laccaria bicolor during their in vitro interaction. In this context, in order to increase knowledge concerning MHB/ECM interactions, the work presented here focuses on the physical interaction between these two organisms. To this purpose, a method of analysis based on confocal microscopy was developed. The results showed that the bacteria formed biofilms preferentially localized on the apical region of the ECM colonies, which could indicate a trophic interaction. Such an interaction has been subsequently confirmed. The results also showed that the physical interaction between L. bicolor and BBc6 is not specific since all thirteen other bacterial strains tested formed biofilms on the hyphae of L. bicolor. On the other hand, BBc6 was unable to form biofilms on some fungi belonging to Ascomycetes, suggesting the existence of inhibition mechanisms. Moreover, the study of the BBc6 biofilm matrix revealed networks of DNA-containing filaments which seem to structure these biofilms and which have also been observed in all the bacterial strains tested. These results reveal a structural role of the DNA molecule, a role that has been rarely reported so far despite its probable high occurrence. Finally, it has been shown that BBc6 mutants having lost their helper effect presented a modified phenotype concerning their biofilm formation on abiotic surface, suggesting a potential link between the helper effect and the biofilms formation
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Miloud, Youssra. "Etude du potentiel bénéfique des souches de Rhizobium pour Medicago truncatula : symbiose, solubilisation du phosphate et lutte contre la verticilliose." Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0123/document.
Повний текст джерелаАнотація:
En raison de leur capacité à former une symbiose avec des bactéries du sol appelées Rhizobium, ces bactéries fixent l’azote atmosphérique et leurs plantes-hôtes n’ont donc pas besoin de fertilisant azoté, les légumineuses jouent un rôle important dans l'agriculture. En outre, certaines souches de Rhizobium ont la capacité de solubiliser le phosphate, fournissant ainsi du phosphore assimilable aux plantes hôtes. Une aptitude à lutter contre certains agents pathogènes a aussi été démontrée dans plusieurs études. La présente étude évalue l’efficacité symbiotique de rhizobiums tunisiens, leur capacité à solubiliser le phosphate, et leur aptitude à lutter contre la verticilliose ainsi que d’autres champignons pathogènes chez Medicago truncatula. Trente-six isolats de rhizobiums prélevés sur des nodules racinaires de M. truncatula provenant de différentes régions de Tunisie ont été obtenus pour ce travail. Environ 60% de ces isolats étaient capables de solubiliser le phosphate in vitro. Dans une seconde étape, trois rhizobiums solubilisant le phosphate et un isolat incapable de solubiliser le phosphate in vitro ont été utilisés pour des essais en phytotron afin de voir l’effet de la présence des rhizobiums sur les paramètres de croissance des plantes en présence de phosphate inorganique sous forme de CaHPO4 et rocheux sous forme brute. Les résultats de l’essai montrent que les plantes de la lignée A17 traitées au CaHPO4, ont tendance à produire plus de nodules et de biomasse aérienne que la lignée F83005.5 et que la forme du phosphate utilisé, soluble ou non soluble, affecte les paramètres étudiés. L'inoculation de quatre lignées de M. truncatula avec 16 isolats de rhizobium sélectionnés auparavant a montré une interaction significative entre les isolats et les lignées pour la symbiose visible par la formation de nodules. Tous les isolats de rhizobium testés ont augmenté la biomasse aérienne des plantes, réduit la biomasse racinaire et entraîné une teneur plus élevée en azote mais l’effet dépendait de l’isolat de rhizobium et de la lignée de M. truncatula utilisés. Enfin, ces isolats ont été testés pour leur capacité à protéger des plantes de M. truncatula contre une maladie racinaire, la verticilliose. Des activités antagonistes in vitro contre divers champignons pathogènes dont Verticillium et Fusarium ont également été recherchées permettant d’identifier un isolat efficace pour la lutte biologique. Les résultats de cette étude suggèrent que des isolats de rhizobium sélectionnés pourraient être utilisés comme biofertilisants dans les sols pauvres pour réduire l'utilisation d'engrais chimiques azotés et phosphorés mais pas pour lutter contre la verticillioseBecause of their ability to form a symbiosis with soil bacteria called Rhizobium, legumes play an important role in agriculture. These bacteria fix atmospheric nitrogen; hence their host plants do not need nitrogen fertilizers. In addition, some strains of Rhizobium have the ability to solubilize phosphate, thus providing phosphorus to host plants. An ability to control certain pathogens has also been demonstrated in several studies. The present study evaluates the symbiotic efficiency of Tunisian rhizobia, their ability to solubilize phosphate, and their ability to control Verticillium wilt and other pathogenic fungi in Medicago truncatula. Thirty-six rhizobial isolates were obtained from root nodules of M. truncatula from different parts of Tunisia were used in this work. About 60% of these isolates were able to solubilize phosphate in vitro. In a second step, three phosphate solubilizing rhizobia and one isolate unable to solubilize phosphate in vitro were used for phytotron assays to see the effect of the presence of rhizobia on plant growth parameters in the presence of soluble and insoluble forms of phosphate. The results of the experiment show that A17 plants treated with CaHPO4, tend to produce more nodules and shoot biomass than F83005.5 and that the phosphate form used, soluble or non-soluble, affects parameters studied. Inoculation of four M. truncatula lines with 16 previously selected rhizobial isolates showed significant interaction between isolates and lines for symbiotic abilities as visualised by nodule formation. All rhizobial isolates tested increased above-ground biomass, reduced root biomass, and increased nitrogen content with strains effects of plant genotype and bacterial isolate. Finallly, these isolates were tested for their ability to protect M. truncatula plants against Verticillium wilt, and to inhibit the growth of pathogenic fungi such as Verticillium and Fusarium in vitro. However, no isolate could be identified as effective for biological control. The results of this study suggest that selected rhizobial isolates could be used as biofertilizers in poor soils to reduce the use of nitrogen and phosphorus fertilizers but not to control Verticillium wilt
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Irshad, Usman. "Relations trophiques dans la rhizosphère : effet des interactions entre champignon ectomycorhizien, bactéries et nématodes bactérivores sur le prélèvement minéral du Pin maritime (Pinus pinaster)." Thesis, Montpellier, SupAgro, 2011. http://www.theses.fr/2011NSAM0029/document.
Повний текст джерелаАнотація:
Les microorganismes agissent comme un puits et une source de N et Pdisponibles car ils sont responsables des cycles biogéochimiques de N et P. La bouclemicrobienne, basée sur la prédation des bactéries par les microprédateurs tels que lesnématodes bactérivores, est considérée comme un facteur majeur de la minéralisation de Net de P dans les écosystèmes terrestres. Cependant, peu de données sont disponibles surl'impact de la prédation par les nématodes sur la nutrition minérale des plantes ligneusesectomycorhizées. Différentes expérimentations ont été conduites pour quantifier le rôle dela prédation des bactéries par les nématodes sur l'architecture et la croissance racinaire, lanutrition minérale (N et P) d'une espèce ligneuse, Pinus pinaster, associée ou non avec lebasidiomycète ectomycorhizien Hebeloma cylindrosporum. Les plantes ont été cultivéesdans un système expérimental simplifié et stérile, et inoculées ou non avec Bacillus subtiliset des nématodes bactérivores (de la famille des Rhabditidae ou des Cephalobidae) isolés àpartir d'ectomycorhizes et de sol provenant d'une plantation de Pin maritime. L'effet de laprédation sur la croissance des plantes et le devenir du 15N bactérien vers les partiesaériennes dépend très fortement de la disponibilité en P du milieu. De plus, la prédationdes bactéries est indispensable pour permettre à la plante d'utiliser le P du phytate, unesource de P organique très peu disponible pour la plante mais très facilement utilisable parB. subtilis car cette bactérie est capable de libérer de la phytase dans le milieu. Cesrésultats ouvrent de nouvelles perspectives pour améliorer l'utilisation du phytate pour lanutrition phosphatée des plantesSoil microorganisms act as a sink and a source of available N and P bymediating key processes in the biogeochemical N and P cycling. The microbial loop, basedupon the grazing of bacteria by predators such as bacterial-feeding nematodes, is thoughtto play a major role in the mineralization of nutrients such as nitrogen (N) and phosphorus(P) in terrestrial ecosystems. However, little is known about the impact of grazing bynematodes on mineral nutrition of ectomycorrhizal woody plants. Different studies wereundertaken to quantify the role of nematode grazing on bacteria on the root growth andarchitecture, mineral nutrition (N and P) of a woody species, Pinus pinaster, whether ornot associated with the ectomycorrhizal basidiomycete Hebeloma cylindrosporum. Plantswere grown in a sterile simplified experimental system, whether inoculated or not withBacillus subtilis and bacterial-feeding nematodes (belonging to Rhabditidae orCephalobidae families) that were isolated from ectomycorrhizae and from soil of a P.pinaster plantation. The effect of nematode grazing on plant growth and the fate ofbacterial 15N towards plant shoots was strongly dependent upon medium P availability. Inaddition, nematode grazing was required to enable the plant to access P from phytate, awell-known poorly available P source to plants but that was used by bacterial populationsof B. subtilis due to its ability to release phytase in the medium. These results open analternative route to increase the use of phytate for plant P nutrition
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Sudakaran, Sailendharan [Verfasser], Rolf G. [Akademischer Betreuer] Beutel, Martin [Akademischer Betreuer] Kaltenpoth, and Andreas [Akademischer Betreuer] Brune. "Evolution of mutualistic microbiome in firebugs and cotton stainers (Hemiptera; Pyrrhocoridae) : characterizing the role of bacterial symbionts in diversification and niche expansion of Pyrrhocoridae / Sailendharan Sudakaran. Gutachter: Rolf Georg Beutel ; Martin Kaltenpoth ; Andreas Brune." Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2015. http://d-nb.info/1079217819/34.
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Sudakaran, Sailendharan Verfasser], Rolf G. [Akademischer Betreuer] [Beutel, Martin [Akademischer Betreuer] Kaltenpoth, and Andreas [Akademischer Betreuer] Brune. "Evolution of mutualistic microbiome in firebugs and cotton stainers (Hemiptera; Pyrrhocoridae) : characterizing the role of bacterial symbionts in diversification and niche expansion of Pyrrhocoridae / Sailendharan Sudakaran. Gutachter: Rolf Georg Beutel ; Martin Kaltenpoth ; Andreas Brune." Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2015. http://d-nb.info/1079217819/34.
Повний текст джерела