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1
Fracchia, Félix. "Les phytohormones, des régulateurs clefs du microbiote du peuplier ?" Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0217.
Abstract:
Les écosystèmes forestiers sont des environnements dynamiques aussi bien à l'échelle macroscopique que microscopique. Les arbres abritent un vaste cortège de microorganismes, appelé microbiote, majoritairement constitué de bactéries et de champignons. Ces communautés microbiennes colonisent les différents tissus des arbres et participent à diverses interactions, aussi bien défavorables (e.g. pathogènes), que bénéfiques. En effet, certains microorganismes (e.g. Plant Growth Promoting Bacteria : PGPR ; champignons mycorhiziens), améliorent la croissance et le développement de leur hôte via le transfert de nutriments, principalement de l'azote (N) et du phosphore (P) en échange de sucres photo-assimilés. D'autre part, il confère une résistance à l'arbre face aux stress biotiques (e.g. attaque par des pathogène, herbivorie) et abiotiques (e.g. sécheresse, toxicité des sols). L'assemblage de ce microbiote est un processus dynamique dans le temps et dans l'espace. Chaque organe de l'hôte constitue un micro-habitat particulier où s'établissent des communautés microbiennes spécifiques, aussi bien à la surface (épiphytique) qu'à l'intérieur des différents compartiments (endophytique). D'autre part, l'établissement du microbiote conduit à une succession de microorganismes qui remplacent les communautés déjà présentes au cours du temps. Il existe différents paramètres, biotiques (e.g. rhizodéposition, immunité et génotype de l'hôte) et abiotiques (e.g. type de sol, climat, saisons), qui régulent l'assemblage des communautés microbiennes. Dans ce contexte, l'objectif de cette thèse est de caractériser l'influence des phytohormones dans l'assemblage du microbiote du peuplier. Nous avons déterminé dans un premier temps, la dynamique de colonisation microbienne du système racinaire de plantules de peupliers de 2 à 50 jours. En utilisant deux méthodes complémentaires, le séquençage de marqueurs taxonomiques bactériens (16S) et fongiques (ITS, 18S), et l'observation des systèmes racinaires au microscope confocal à balyage laser (CLSM), nous avons mis en évidence l'existence de vagues successives de colonisation conduisant au remplacement progressif de microorganismes. A l'aide des mêmes approches, nous avons caractérisé la dynamique de colonisation du microbiote foliaire. Comme les systèmes racinaires, l'assemblage des communautés microbiennes était dynamique dans le temps. Les microorganismes racinaires et aériens étaient très proches aux temps précoces de colonisation et se différenciaient au cours du temps. Cette observation suggère le transfert de microorganismes depuis les racines vers les feuilles conduisant à la sélection de communautés microbiennes spécifiques en fonction des compartiments de l'hôte. Pour analyser le rôle des phytohormones, sur l'assemblage des communautés microbiennes, nous avons généré des lignées transgéniques de peupliers altérées dans la biosynthèse et la perception de l'acide gibbérellique (AG), l'acide jasmonique (AJ), l'acide salicylique (AS), l'éthylène (ET) et des terpènes. Dans un premier temps, nous avons utilisé des lignées transgéniques de peuplier altérées dans la régulation de l'ET. Nous avons démontré que l'ET n'altère pas la composition des exsudats racinaires, au contraire des métabolomes aériens et racinaires qui étaient modulés en fonction de la concentration d'ET produit. D'autre part, nous avons observé une influence directe et globale de l'ET sur la structure du microbiote après séquençage de marqueurs taxonomiques bactériens (ITS) et fongiques (16S), et l'observation des systèmes racinaires au CLSM. Enfin, afin d'exclure tout cofacteur pouvant expliquer les variations du microbiote chez des lignées transgéniques, nous avons caractérisé l'influence de l'agro-transformation sans expression de transgène sur la composition des communautés microbiennes. Nous avons démontré que cet évènement de transformation altérait l'assemblage du microbiote en comparaison avec des peupliers sauvagesForest ecosystems are dynamic environments on both the macroscopic and microscopic scales. Trees are home to a vast array of microorganisms, called microbiota, mainly composed of bacteria and fungi. These microbial communities colonize the different tissues of trees and participate in various interactions, both detrimental (e.g. pathogens) and beneficial. Indeed, some microorganisms (e.g. Plant Growth Promoting Bacteria: PGPR; mycorrhizal fungi), improve the growth and development of their host via the transfer of nutrients, mainly nitrogen (N) and phosphorus (P) in exchange of photoassimilated sugars. On the other hand, it confers resistance to the tree in the face of biotic stresses (e.g. attack by pathogens, herbivory) and abiotic stresses (e.g. drought, soil toxicity). The assembly of this microbiota is a dynamic process in time and space. Each organ of the host constitutes a particular micro-habitat where specific microbial communities are established, both on the surface (epiphytic) and within the different compartments (endophytic). On the other hand, the establishment of the microbiota leads to a succession of microorganisms that replace the communities already present over time. There are different parameters, biotic (e.g. rhizodeposition, immunity and host genotype) and abiotic (e.g. soil type, climate, seasons), that regulate the assembly of microbial communities. In this context, the objective of this thesis is to characterize the influence of phytohormones in the assembly of poplar microbiota. We first determined the dynamics of microbial colonization of the root system of poplar seedlings from 2 to 50 days. Using two complementary methods, sequencing of bacterial (16S) and fungal (ITS, 18S) taxonomic markers, and observation of the root systems with a confocal laser scanning microscope (CLSM), we demonstrated the existence of successive waves of colonization leading to the progressive replacement of microorganisms. Using the same approaches, we characterized the colonization dynamics of the leaf microbiota. Like root systems, the assembly of microbial communities was dynamic over time. Root and aerial microorganisms were very close at early colonization times and differentiated over time. This observation suggests the transfer of microorganisms from roots to leaves leading to the selection of specific microbial communities according to host compartments. To analyze the role of phytohormones on the assembly of microbial communities, we generated transgenic lines of poplars altered in the biosynthesis and perception of gibberellic acid (GA), jasmonic acid (JA), salicylic acid (SA), ethylene (ET) and terpenes. First, we used poplar transgenic lines altered in the regulation of ET. We demonstrated that ET does not alter the composition of root exudates, in contrast to aerial and root metabolomes that were modulated according to the concentration of ET produced. On the other hand, we observed a direct and global influence of ET on the structure of the microbiota after sequencing of bacterial (ITS) and fungal (16S) taxonomic markers, and observation of root systems at CLSM. Finally, in order to exclude any cofactor that could explain microbiota variations in transgenic lines, we characterized the influence of agro-transformation without transgene expression on microbial community composition. We demonstrated that this transformation event altered the assembly of the microbiota in comparison with wild type poplars
2
Bourdes, Pierre-Alexandre. "Aminotransferases in rhizobia-legume symbiosis." Thesis, University of Reading, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506071.
3
Sinyanya, Kolisa Yola. "Phenotypic characterization of rhizobia isolates and distribution of Burkholderia rhizobia in the Core Cape Subregion." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20335.
Abstract:
The Core Cape Sub-region is well known for its low nutrient, low pH soils which harbour a variety of alpha and beta- Proteobacteria associated with a diversity of legume species. Soil bacteria are important for ecological processes and are influenced mostly by edaphic factors such as salinity and pH, and climatic conditions such as temperature. Recent studies have shown that Burkholderia form nitrogen fixing molecular associations with members of, among others, tribes Crotalarieae, Podalyrieae and Indigofereae. Selected rhizobia that included Burkholderia and Mesorhizobia, the large genera in the isolated rhizobia, and representing beta- and alpha- Proteobacteria were phenotypically characterized to determine the tolerances of Cape isolates to abiotic conditions. In a second study, glasshouse trapping experiments were conducted using legume species Podalyria calyptrata and Indigofera filifolia grown in 13 soils collected from diverse localities of the CCR, to determine the phylogenetic distribution of Burkholderia species in diverse soils of the CCR. To phenotypically characterize rhizobia isolated from a previous study, 29 isolates from representative legume-nodules of 13 different localities were grown under laboratory conditions. Isolates were phenotypically characterized for colony morphology, growth temperature, carbon source, salinity and pH tolerance. Morphological results revealed that majority of the tested isolates were white opaque, rod shaped and fast growing. Exceptions were found in colour where five strains produced a milky pigment, two were watery translucent; observation of bacteriod-shape among six symbionts; and one isolate grew after 7 days.
4
Alexandre, Ana Isabel Pereira. "Temperature stress tolerance in chickpea rhizobia." Doctoral thesis, Universidade de Évora, 2010. http://hdl.handle.net/10174/11582.
Abstract:
The aims of the present thesis were to study the chickpea rhizobia diversity and biogeography using Portugal as case study; to evaluate the temperature stress tolerance of the isolates, and to investigate the molecular basis of stress tolerance. The phylogenetic performance of the co-chaperone dnaJ was also addressed, in order to find an altemative marker to 16S rRNA gene. According to the 16S rRNA gene phylogeny, most isolates were found to be distinct from the typical chickpea rhizobia species, Mesorhizobium cíceri and M. mediterraneum. Some provinces of origin are associated with particular species groups. dnaJ was found to be a Useful phylogenetic marker for Mesorhizobium and for the Alphaproteobactería class. The evaluation of temperature stress tolerance revealed tolerant and sensitive isolates to both
heat and cold. Analysis of the expression of dnaK and groESL chaperone genes suggested that higher induction of these genes is related to higher tolerance to heat. ### - Resumo - A presente tese teve como objectivos o estudo da diversidade e biogeografia de rizóbio de grão-de-bico em Portugal, a avaliação da tolerância dos rizóbios ao stress térmico, bem
como o estudo das bases moleculares da tolerância ao stress. Estudou-se, ainda, o gene da co-chaperone dnaJ do ponto de vista filogenético.
A filogenia baseada no gene 16S rRNA revelou que a maior parte dos rizóbios de grão-de-bico agrupam com outras espécies, que não as típicas desta leguminosa (Mesorhizobium cicerí e M. mediterraneum). Encontrou-se uma associação entre algumas províncias e determinadas espécies de rizóbio. O gene dnaJ revelou-se um bom marcador filogenético para Mesorhizobium, bem como para a classe Alphaproteobactería. A avaliação da tolerância à temperatura permitiu diferenciar isolados tolerantes e sensíveis, a altas e baixas temperaturas. A análise da expressão dos genes dnaK e groESL, sugeriu que uma maior indução destes genes está relacionada com maior tolerância a altas temperaturas.
5
Beauregard, Marie-Soleil. "Characterization of rhizobia nodulating Trifolium ambigum M.B." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81246.
Abstract:
Phenotypic characterizations demonstrated that diversity among 19 naturalized North American and 5 commercial Kura clover ( Trifolium ambiguum M.B.) rhizobial strains was limited. Growth chamber and field evaluations indicated the superiority of North American isolates, increasing foliage accumulation by 30% when compared to commercial inoculant strains. Nitrogen fertilization, however, produced greater accumulations in all evaluations. Genetic diversity among 128 isolates from the lower Caucasus was significant. Nodulation specificity of rhizobia from the lower Caucasus was demonstrated to be more complex than what was reported in the literature, as plants of different ploidy levels and even of different species were, in some cases, nodulated by the same isolate. Specificity of a given rhizobial strain varied depending on the isolate. This study identified naturalized North American rhizobial isolates that are more efficient than currently used commercial strains and increased the genetic diversity of Kura clover rhizobia currently available.
6
Casteriano, Andrea Veronica. "Physiological mechanisms of desiccation tolerance in Rhizobia." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/10423.
Abstract:
One of the main factors affecting the survival of rhizobia on seed is desiccation stress. The poor survival of rhizobia affects nodulation, nitrogen fixation and legume yield. A better understanding of desiccation tolerance and how it may be enhanced may contribute to the development of strategies to improve survival of rhizobia on seed. This study aimed to improve the survival of rhizobia by enhancing inherent mechanisms of desiccation tolerance through the manipulation of the growth medium. Accumulation of intracellular trehalose by rhizobia increases in response to osmotic and desiccation stress, and has also been related to an improved capacity for desiccation tolerance. In this study, a linear relationship was observed between intracellular trehalose accumulation in Rhizobium leguminosarum bv. trifolii (TA1) and Bradyrhizobium japonicum (CB1809) and increasing osmotic pressure of a defined growth medium (JMM) from 1.0 atm to 2.8 atm. Although increased concentrations of intracellular trehalose did not improve survival of rhizobia immediately after vacuum drying, survival was significantly improved after 10 days of storage at low relative humidity (9%). Resuspending rhizobia in trehalose solution, to provide external protection to cells during drying, significantly increased survival immediately after drying and storage. The increased protection during drying allowed the positive effect of intracellular trehalose on rhizobial survival to be observed. Cells of TA1 and CB1809 extracted from peat after solid-state fermentation survived significantly better immediately after vacuum drying (22-fold and 5-fold respectively) and during storage than cells grown in JMM (1.0 atm). However, it was difficult to extract adequate V cell mass to measure intracellular trehalose and consequently cells were grown in water extracts of peat to simulate the conditions that rhizobia would be exposed to in traditional peat cultures. Growing TA1 and CB1809 in aqueous peat extract increased trehalose accumulation compared to cells grown in JMM and also significantly improved survival (18-fold) of TA1. Although survival of CB1809 was generally improved after growth in peat extract, it was not significantly different to cells grown in JMM. Cells grown in peat extract exhibited changes in cell morphology and protein expression similar to those observed after solid-state fermentation in peat. Electron microscopy revealed the accumulation of an electron-dense material around the plasma membrane that occupied the periplasmic space in both TA1 and CB1809. Similar changes to cell morphology have been previously linked to improved survival. Peptide analysis by liquid chromatography-mass spectrometry indicated increased expression of stress response proteins in TA1 and CB1809 after growth in peat extract. Some of those proteins included membrane repair proteins (PspA) and proteins generated to combat periplasmic stress (OstA) and oxidative damage (thioredoxin). A cell viability assay using alamarBlue® reagent showed that growing rhizobia in peat extract reduces metabolic activity compared to that of cells grown in JMM, and membrane integrity analysis of the same cells using a LIVE/DEAD® viability kit showed that peat extract increased membrane permeability to propidium iodide (PI). Environmental stresses have been reported to cause reversible changes to membrane function and permeability, demonstrated by changes in PI-uptake. This finding, together with the changes in cell morphology and increased expression of stress response proteins, suggests that improved survival after growth of rhizobia in peat extract is related to adaptive changes of cells in response to water-extractable constituents of peat. VI Findings from this work suggest that desiccation tolerance in rhizobia is a multifactorial process that involves the accumulation of trehalose together with the expression of proteins involved in maintaining cell envelope integrity and stability, as well as the repair and prevention of DNA and protein damage caused by oxidative stress. Determining chemical elicitors of adaptive changes in cells may assist in further development of inoculant technology to improve survival of rhizobia on seed.
7
Harrison, Robert. "Domesticating Lebeckia ambigua: Solving the rhizobia issues." Thesis, Harrison, Robert (2017) Domesticating Lebeckia ambigua: Solving the rhizobia issues. Honours thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/39770/.
Abstract:
Permanent dryland pastures are under-utilised in southern Australia (Angus and Peoples 2012), possibly due to the lack of well adapted perennial legume species that can fit into current farming systems. Lebeckia ambigua has been proposed as a candidate to fill this void with its adaptability to drought, acidic and infertile soils in low rainfall areas (Howieson et al. 2013). The research on L. ambigua has so far focussed on deep, sandy soils where cropping is problematic. Increasing the soil fertility in these previously low-profitable regions could provide mixed farming production with a comparative advantage over continuous cropping (Angus and Peoples 2012). However, the successful incorporation of L. ambigua into an agricultural system will require an understanding of its symbiont, Burkholderia species. Although L. ambigua and Burkholderia spp. have only recently been identified for domestication into agriculture (Howieson et al. 2013), researchers have had success with cultivating them throughout southern Western Australia (WA), except with inoculation.
There is a challenge to keep the inoculant B. spp. alive, in a peat carrier, when coated onto L. ambigua seed for sowing in a drying environment. Clay granules, as an alternative carrier, have previously been shown to be unable to carry high numbers of cells of B. spp. (Howieson et al. 2013). Field experiments with amended clay granules carrying B. spp. produced nodules on L. ambigua, albeit not in large number. Attempts at quantifying the numbers of cells in the amended granules, by resuscitating B. spp. from them using antibiotic media and plant infection techniques, were unsuccessful. However, antibiotic profiling of B. spp. strains identified chloramphenicol (20μg/ml) in YMA as an excellent media to suppress contaminants in the clay to facilitate enumeration.
Recently recovered strains of B. spp. were assessed alongside previous strains for tolerance to desiccation, which gave rise to a set of possible strains that could surpass the commonly used strain in this regard (WSM4204). Although clay granules were indicated to hold B. spp. cells sufficient for nodulation in the field, further studies must focus on the optimisation of a suitable inoculant technology for L. ambigua. The B. spp. and strain differences in tolerance to desiccation identified in this work may assist this target.
8
Cepeda, Hernandez Martha Lucia. "Phenotypic characterization of rhizobia that nodulate ball clover." Texas A&M University, 2005. http://hdl.handle.net/1969.1/2636.
Abstract:
A total of 43 Rhizobium leguminosarium bv. trifolii isolates were obtained from
soil samples of two ball clover (Trifolium nigrescens) pastures from Iola and Kilgore
(Texas) using ball clover as capture plants. The isolates were phenotypically
characterized by intrinsic antibiotic resistance (IAR) against a range of concentrations of
eight antibiotics, and by the utilization of 95 different carbon sources (BIOLOG system).
The rhizobial isolates were also evaluated for their tolerance to salinity, high
temperatures and low pH. The isolates showed two different ranges of growth rates:
fast-growing (doubling times between 1.4 - 3.7 h) and slow- growing isolates (12.3 -
21.3 h). The numerical analysis of the phenotypic characteristics showed that the 43
isolates could be grouped in 24 different strains. Cluster analysis based on sensitivity
responses of IAR, metabolic profiles of BIOLOG and salt, temperature and acidity
tolerance levels could distinguish the Rhizobium strains from a Pseudomonas isolate.
The analysis also showed that the rhizobial strains isolated from ball clover nodules are
different from a commercial R. leguminosarium bv. trifolii strain used as inoculant for
this legume.
9
Solaiman, Abu Rayhan Mohammad. "Influence of soil acidity factors on Lotus rhizobia." Thesis, Queen's University Belfast, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356972.
10
Octive, Jerome C. "Mutagenic effects of aluminium on rhizobia and bradrhizobia." Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278065.
11
Pfau, Thomas. "Modelling metabolic interactions in the legume-rhizobia symbiosis." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=202144.
Abstract:
With the emergence of "omics" techniques, it has become essential to develop tools to utilise the vast amount of data produced by these methods. Genome-scale metabolic models represent the mathematical essence of metabolism and can easily be linked to the data from omics sources. Such models can be used for various analyses, including the investigation of metabolic responses to changing environmental conditions. Legumes are known for their ability to form a nitrogen-fixing symbiosis with rhizobia, a vital process that provides the biosphere with the majority of its nitrogen content. In the present thesis, a genome-scale metabolic model for the legume Medicago truncatula was reconstructed, based on the annotated genome sequence and the MedicCyc database. A novel approach was employed to define the compartmentalisation of the plant's metabolism. The model was used to calculate the biosynthetic costs of biomass precursors (e.g. amino acids, sugars, fatty acids, nucleotides), and its capability to produce biomass in experimentally observed ratios was demonstrated using flux balance analysis. Further investigation was carried out into how the biosynthesis fluxes and costs change with respect to different nitrogen sources. The precise charge balancing of all reactions in the model allowed the investigation of the effects of charge transport over the cellular membrane. The simulations showed a good agreement with experimentaldata in using different sources of nitrogen (ammonium and nitrate) to minimise the charge transport of the membrane. To allow the investigation of the symbiotic relationship, two rhizobial models were used. The first model, for Sinorhizobium meliloti, was reconstructed from the MetaCyc database (MC-model); the second model was a recently published model for S. meliloti specialised for symbiotic nitrogen xation (SNF-model). Combined models were created for both rhizobial networks using a specialised nodule submodel of the plant model. Potential interactions were extracted from the literature and investigated, with the analysis suggesting that oxygen availability is the main limitation factor in symbiotic nitrogen fixation. Within the analysis the SNF-model appeared to be too restricted and lacking the potential for sufficient nitrogen xation; therefore, further analysis was carried out using the MC-model, upon which it was observed that the availability of oxygen can also influence how nitrogen is supplied to the plant. At high oxygen concentrations ammonia is the primary form of nitrogen supplied by the rhizobium. However, the simulations, in accordance with experimental data, show that at lower concentrations of oxygen, alanine takes precedence. The findings also support the concept of amino acid cycling as a potential way to improve nitrogen fixation. The more flexible MetaCyc based model has allowed other potential genetic engineering approaches for higher nitrogen fixation yields to be proposed.
12
Qu, Yihan. "Molecular Analysis of Effectiveness in Soybean-Rhizobia Symbioses." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/18831.
Abstract:
Soybean-rhizobia symbioses can be highly variable in nitrogen fixing effectiveness. Identification of the genetic regulation for symbiotic effectiveness could enable improvement of the understanding and manipulation of biological nitrogen fixation (BNF). The aim of this study is to evaluate effectiveness of symbioses between a range of soybean cultivars and rhizobial strains, and identify genomic traits that account for differences between highly and poorly effective N2 fixing strains. In this study, thirteen strains from genera Bradyrhizobium and Sinorhizobium were differentiated using their ribosomal fingerprints and phylogenies based on symbiotic and housekeeping genes. The selected strains were evaluated for their symbiotic efficiency with six soybean cultivars in three glasshouse experiments. Greatly varied symbiotic outcomes were observed due to highly variable compatibility between symbiotic partners. A poorly effective N2 fixing B. elkanii strain CC717 caused sub-optimal BNF on five out of the six tested cultivars. A time-course experiment showed CC717 induced nitrogen fixation activity to decrease five weeks after sowing, and early nodule senescence coupled with leaf senescence and minor foliar chlorosis in soybean cv. Soya 791. Whole genome sequencing yielded a large number of contigs for the poorly effective strain CC717, indicating a high volume of repeated sequences in this genome. The genome of a highly effective N2 fixing B. diazoefficiens strain CB1809 showed highly conserved similarity to its type strain USDA110. However, no direct relatedness was found between the level of conservation of the symbiotic region and the symbiotic efficiency. The BNF efficiency is likely to be controlled by specific genes of both host and rhizobia e.g., the rhizobial T3SS and soybean Rj genes. The results obtained in this study provide important information for better understanding and future manipulation of rhizobia-associated biological nitrogen fixation.
13
Amiri, Alireza Agha. "Regulation of nitrogen fixation in rhizobia-legume symbioses." Thesis, Amiri, Alireza Agha (2021) Regulation of nitrogen fixation in rhizobia-legume symbioses. Honours thesis, Murdoch University, 2021. https://researchrepository.murdoch.edu.au/id/eprint/63559/.
Abstract:
Rhizobia are soil-dwelling bacteria capable of infecting legume roots and forming a symbiotic association. Inside root nodules, low O2 levels trigger expression of the nitrogenase enzyme complex in rhizobia, allowing them to fix atmospheric N2 into NH3, and secrete this reduced nitrogen source to the host plant. Rhizobial N2 fixation is activated via the transcriptional regulator NifA, which is itself induced by low O2 concentration in legume root nodules, most commonly via the two-component sensor-regulator FixLJ or a modified version of this regulon. For rhizobia in the genus Mesorhizobium, it is currently unclear how low O2 tension is sensed and transduced into a signal to activate N2 fixation, with the FixLJ system shown to be dispensable for N2 fixation. Mesorhizobium ciceri CC1192, which forms a symbiosis with Cicer arietinum (chickpea) and is the commercial inoculant for this crop legume in Australia, harbours fixV, a putative LacI/GalR transcriptional regulator which may directly control the expression of nifA in this strain. To investigate the role of fixV and nifA within CC1192, inactivation vectors were constructed in the suicide vector pJQ200SK via Gibson Assembly and fixV and nifA deletion mutants generated, along with a nitrogenase null mutant (nifH) as a non-N2-fixing control. nifH mutants were symbiotically defective on C. arietinum, with nitrogenase activity completely abolished. Deletion of fixV resulted in reduced, but not abolished, nitrogenase activity on a per nodule basis and reduced foliage dry weights, while the ΔnifA mutant phenotype remains to be tested. FixV, therefore, is not essential for N2 fixation in CC1192 but likely plays a vital role alongside another as yet unidentified regulator.
14
Waldon, Hollis B. "Sonoran Desert Rhizobia Found to Nodulate Acacia constricta." University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/554231.
15
Moulin, Lionel. "Etude moléculaire de la diversité symbiotique des rhizobia : de l'analyse du gène nodA à l'identification de rhizobia au sein des bé̀ta-protéobactéries." Lyon 1, 2002. http://www.theses.fr/2002LYO10179.
Abstract:
Les rhizobia sont des bactéries du sol capables d'établir une symbiose fixatrice d'azote avec des légumineuses. Le séquençage et l'analyse phylogénétique du gène de nodulation nodA d'une collection de rhizobia taxonomiquement et symbiotiquement divers a permis d'établir l'existence d'une étroite corrélation entre la séquence protéique NodA et la présence de trois substitutions particulières des FNs. Nous avons développé une méthode de prédiction de la présence de ces substitutions basée sur l'analyse phylogénétique et statistique de la séquence NodA. La caractérisation du gène nodA parmi des souches de Burkholderia et Ralstonia isolées de nodules de légumineuses nous a conduit à démontrer l'existence de véritables rhizobium au sein des béta-protéobactéries, révélant ainsi l'étonnante diversité taxonomique des rhizobia. La construction de filtres ADN dédiés à leur identification et à leur caractérisation symbiotique a été entreprise à partir d'une collection de gènes nod spécifiques aux rhizobia.
16
Peele, Price Jason. "Control of RNA Structure by CspA Proteins in Rhizobia." Thesis, Washington State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10605605.
Abstract:
Rhizobia are soil bacteria that can associate with some legumes and participate in symbiotic nitrogen fixation. Bacterial CspA family members are small, single stranded nucleic acid binding proteins conserved throughout all domains of life. Here, the role of CspA family proteins in the symbiotic development of Sinorhizobium meliloti with Medicago sativa (alfalfa) is investigated. Expression and genetic deletion strain analysis revealed that CspA family proteins are differentially expressed in symbiosis and contribute to symbiotic effectiveness. RNAseq analysis of native co-immunoprecipitated RNAs identified a novel interaction between several CspA family proteins and the αR14 family of small non-coding RNA (sRNAs). Whole transcriptome analysis defined transcriptional defects associated with loss of CspA function. The development of a new in vitro RNA binding assay using broccoli, a Green Fluorescent Protein (GFP) RNA mimic, is described as well as its use in defining binding specificity of CspA family proteins with synthetic and native ?R14 family sRNA structures. This work concludes that CspA family proteins interact with and influence the stability of specific RNA structures and these interactions control RNA regulated processes important for symbiotic development.
17
Morieri, Giulia. "Two types of calcium signalling in legume-rhizobia symbiosis." Thesis, University of East Anglia, 2010. https://ueaeprints.uea.ac.uk/31683/.
18
Laranjo, Marta. "Genetic diversity and symbiotic effectiveness of chickpea rhizobia strains." Doctoral thesis, Universidade de Évora, 2007. http://hdl.handle.net/10174/11260.
Abstract:
Rhizobia are soil bacteria able to establish nitrogen-fixing symbioses with leguminous plants inside special root tissues, the nodules. These symbioses are of extreme importance in agriculture allowing many plant crops to be cultivated without the need for chemical fertilisers.
In the present thesis work, the genetic diversity, phylogeny and symbiotic effectiveness (SE) of native rhizobia, able to nodulate chickpea (Citar arietinum L.), have been addressed.
Forty-one chickpea rhizobia isolated from four different Portuguesa soils (Beja, Elvas, Elvas- ENMP and Évora) were phenotypically evaluated. Twenty-one isolates were further analysed and assigned to the genus Mesorhizobium based on their 16S rDNA sequentes. Highly diverse Mesorhizobium strains were identified, belonging to six different species groups: M ciceri and M mediterraneum, the expected known chickpea symbionts, M loti, M tianshanense, and two probably new species.
A correlation was found between 16S rDNA species groups and origin of individual isolates.
Rhizobial diversity of the forty-one isolates from natural populations was assessed by molecular methods, namely 16S rDNA restriction fragment length polymorphism (RFLP) analysis, plasmid profiles, direct amplified polymorphic DNA (DAPD) fingerprinting and SDS–PAGE analysis of protein profiles. Plasmid number of isolates ranged from zero to six and was found to be correlated with origin and with species groups. 16S rDNA RFLP, DAPD and protein profiles generated analogous clustering of the isolates, supporting results on 16S rDNA sequence based phylogeny of the subgroup of twenty-one isolates. DAPD analysis, a newly described PCR-based approach, proved to be the most discriminating approach in strain differentiation and can be used as a fast method to screen diversity in new isolates. Evaluation of genetic diversity by the four molecular methods showed different levels of heterogeneity in the natural populations. A higher genetic diversity was found in Elvas-ENMP and Beja populations.
The SE determined for the twenty-one isolates as well as for the two chickpea microsymbionts, M ciceri and M mediterraneum, ranged from 4 to 84%. No correlation was depicted between SE and origin site of the isolates. However, Beja isolates show the highest mean. SE, and Elvas-ENMP isolates have the lowest mean SE. We detected no significant correlation between SE and species.
A multilocus phylogenetic approach was used to confirm the molecular phylogeny of the subgroup of twenty-one chickpea rhizobia isolates. Phylogenetic analysis based on the intergenic spacer between 16S and 23S rRNA genes (ITS), the
ATP synthase (atpD) or the DNA recombinase A (recA) sequences corroborated the
16S rDNA phylogeny and confirmed the existence of six distinct species groups
among chickpea mesorhizobia. Further evidence is provided for supporting one of
these evolutionary lineages as new species within the genus Mesorhizobium.
Indeed, sequencing of another housekeeping protein coding gene, the glutamine
synthetase I gene (glnA), from this new group of isolates, confirmed its separate
position and assignment to a new species. The name M. lusitanum is proposed, with
isolate 64b.-Beja as the type strain. A11 isolates from the M. lusitanum group showed a
high symbiotic effectiveness (above 50%) and may be potentially useful field
inoculants.
Chickpea has been considered a restrictive host for nodulation by rhizobia. However, the
present work, as well as other recent studies, have shown that several Mesorhizobium species
may effectively nodulate chickpea. In order to investigate the relationships between
symbiosis genes from different rhizobia species able to nodulate chickpea, the niƒH and nodC
genes from the twenty-one Portuguesa chickpea rhizobia isolates were sequenced and used for
phylogenetic studies.
The phylogenies based on symbiosis genes showed that, regardless of their species
affiliation, ali chickpea rhizobia isolates formed a single highly supported cluster, an evidence
of lateral transfer of symbiosis genes across different species. Chickpea is confirmed as a
non-promiscuous host. The six different rhizobia species, that nodulate chickpea, share
common symbiosis genes, suggesting recognition of only a few Nod factors by chickpea.
Further analysis of symbiosis genes, namely copy number and location, performed by
Southern hybridisation of plasmid profiles suggests the presence of, at least, two symbiosis
plasmids in some isolates. Moreover, we provide evidence for the existence of at least two
copies of the nodC gene in three isolates (6b.-Beja, 29-Beja and EE-29-ENMP), which is
uncommon and has not been reported before in mesorhizobia.
Overall, this work has contributed to the study of diversity and evolutionary relationships
among mesorhizobia and has presented further evidence of horizontal gene transfer among
several species of the genus Mesorhizobium, being the first report on lateral gene transfer
between chickpea mesorhizobia. It has changed the current view on chickpea
microsymbionts, sinta it has revealed that several species of Mesorhizobium can nodulate
chickpea, besides M. ciceri and M. mediterraneum. Furthermore, it has contributed to the
better understanding of the symbiosis between chickpea and rhizobia at the molecular level.
19
Singh, Guriqbal. "Effects of herbicides on nodulation, biological nitrogen fixation and growth of peas (Pisum sativum L.)." Thesis, Bangor University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262763.
20
Rao, J. Raghavendra. "Selection of fast- or slow-growing rhizobia by Lotus species." Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317117.
21
Webster, Gordon. "The interaction between rhizobia and the non-legume Parasponia andersonii." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283646.
22
Mutch, Lesley Anne. "Molecular ecology of rhizobia isolated from native and cultivated Vicieae." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313847.
23
Silva, ValÃria Maria AraÃjo. "Facilitation can increase actinobacteria adaptation capacity and rhizobia "in vitro"." Universidade Federal do CearÃ, 2016. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=17158.
Abstract:
Secretaria da EducaÃÃo do CearÃThe natural environment is marked by an intricate network of biotic interactions that shape the structure of ecological communities. The presence of positive ecological interactions between microbial populations in soils semiarid regions, has great importance in structuring the local soil microbiota. In this work, actinomycetes strains of rhizobia and coming from rhizosphere of Park National Ubajara-CE, were evaluated for the ability to grow through cooperative metabolic mechanisms. Of the 27 evaluated actinomycetes, 22 showed compatibility with rhizobia. The strains UB-05, UB-07, UB-08, UB-11 and UB-21 stood out in facilitating tests for amylase and cellulase. The metabolic activity of actinomycetes helped the development of rhizobia strains
O ambiente natural à marcado por uma intrincada rede de interaÃÃes biÃticas que moldam a estrutura das comunidades ecolÃgicas. A presenÃa de interaÃÃes ecolÃgicas positivas entre populaÃÃes microbianas em solos de regiÃes semiÃridas, possui grande relevÃncia na estruturaÃÃo da microbiota do solo local. Neste trabalho, cepas de actinobactÃrias e rizÃbios oriundas de solo rizosfÃrico do Parque Nacional de Ubajara-CE, foram avaliadas quanto à capacidade de crescerem atravÃs de mecanismos metabÃlicos cooperativos. Das 27 actinobactÃrias avaliadas, 22 apresentaram compatibilidade com rizÃbios. As cepas UB-05, UB-07, UB-08, UB-11 e UB-21, destacaram-se nos ensaios de facilitaÃÃo para amilase e celulase. A atividade metabÃlica de actinobactÃrias auxiliou o desenvolvimento das cepas de rizÃbios.
24
Silva, José Rodrigo da. "Improvement of chickpea rhizobia by genetic transformation with symbiosis genes." Doctoral thesis, Universidade de Évora, 2018. http://hdl.handle.net/10174/23169.
Abstract:
Rhizobia are soil bacteria able to induce the formation of nodules in leguminous plants
and convert atmospheric nitrogen into assimilable forms to these plants. Some
Mesorhizobium species establish symbiosis with chickpea and can increase productivity
of this culture. Rhizobia symbiosis genes, such as nod and nif, are involved in nodule
development and nitrogen fixation. Nevertheless, genes involved in other molecular
mechanisms, namely stress response may influence the symbiotic interaction plantrhizobia.
The objective of this study was to evaluate the effects of overexpressing
symbiotic and stress response genes in the symbiotic performance of chickpea
Mesorhizobium. Mesorhizobium strains were transformed with pRKnifA, pRKnodD,
pRKenvZ and pRKgroEL (expression vector pRK415 with nifA, nodD, envZ and groEL
genes from M. mediterraneum UPM-Ca36T, respectively). From the four strains
transformed with extra nifA copies, only V15-b was able to increase plant biomass, when
compared to wild-type and empty vector strains. Among the four strains transformed with
extra nodD copies, ST-2 and PMI-6 showed a higher symbiotic effectiveness compared
to wild type and control strains. Additional copies of envZ led to in a higher symbiotic
effectiveness when introduced in PMI-6 and EE-7. Evaluation of the symbiotic
effectiveness of the four strains overexpressing groEL showed that only ST-2 improved,
compared to wild-type and empty vector strains. For all these strains the rate of nodule
formation was seen to be higher and further analysis of the infection process and nodule
histological analysis were performed. Overall, this study shows that extra copies of a
given gene may have different effects in the symbiotic effectiveness, depending on the
modified strain. This study contributes to a better understanding of the nodulation and
nitrogen fixation processes, namely regarding the contribution of non-symbiotic genes,
especially envZ, which was to our knowledge for the first time reported to be involved in
the rhizobia-legume symbiosis; Resumo:
Melhoramento de rizóbios de grão-de-bico por transformação genética com genes
simbióticos
Rhizóbios são bactérias capazes de induzir a formação de nódulos em leguminosas e
converter azoto atmosférico em formas assimiláveis por essas plantas. Algumas
espécies de Mesorhizobium estabelecem simbioses com grão-de-bico e conseguem
promover a produtividade desta cultura. Genes simbióticos, como nod e nif, estão
envolvidos na formação dos nódulos e fixação de azoto. No entanto, genes envolvidos
noutros mecanismos, nomeadamente a resposta ao stresse podem influenciar a
interação simbiótica planta-rizóbio. O objetivo deste estudo foi avaliar a eficiência
simbiótica de Mesorhizobium de grão-de-bico sobre-expressando genes simbióticos e
de resposta ao stresse. Estirpes de Mesorhizobium foram transformadas com pRKnifA,
pRKnodD, pRKenvZ e pRKgroEL (vetor de expressão pRK415 com nifA, nodD, envZ e
groEL de M. mediterraneum UPM-Ca36T, respetivamente). Das quatro estirpes
transformadas com cópias extras de nifA, apenas V15-b foi capaz de produzir um
aumento na biomassa das plantas inoculadas, quando comparada às estirpes selvagem
e com vetor vazio. Das quatro estirpes transformadas com cópias extras de nodD, ST-
2 e PMI-6 apresentaram maior eficiência simbiótica em comparação com as estirpes
controlo. Cópias adicionais de envZ resultaram numa maior eficiência simbiótica quando
introduzidas em PMI-6 e EE-7. A avaliação da eficiência simbiótica das quatro estirpes
que sobre-expressam groEL mostrou que apenas a transformação de ST-2 levou a uma
eficiência superior, em comparação com as estirpes selvagem e com vetor vazio. Para
todas estas estirpes, a taxa de formação de nódulos também foi melhorada, pelo que
análises do processo de infeção e da histologia dos nódulos foram efetuadas. Em geral,
este estudo mostra que um gene introduzido pode ter efeitos diferentes na eficiência
simbiótica, dependendo da estirpe modificada. Este estudo contribui para uma melhor
compreensão dos processos de nodulação e fixação de azoto, nomeadamente a
contribuição de genes não-simbióticos, especialmente envZ, que tanto quanto sabemos
não foi previamente descrito como envolvido nestas simbioses.
25
Benezech, Claire. "Développement et étude de systèmes d'interactions tripartites, légumineuses-rhizobia-pathogènes." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30289.
Abstract:
L'azote est un élément essentiel au développement des êtres vivants. Bien qu'il soit présent en grande quantité dans l'air, sous la forme de diazote, il n'est pas directement assimilable par la plupart des êtres vivants. Les légumineuses, par exemple, n'ont pas la capacité de l'assimiler sous cette forme. Cependant, dans un environnement carencé en azote, les plantes sont capables d'interagir avec des bactéries du sol, les rhizobia, qui sont des microorganismes fixateur d'azote atmosphérique grâce à un complexe enzymatique, la nitrogénase. En effet, ces bactéries vont réduire le diazote en ammonium, qui est assimilable par la plante. Les plantes hébergent ces bactéries dans des organes particuliers au niveau de leurs racines, les nodosités, où elles vont leurs fournir des nutriments. La plante tolère au sein de ses propres cellules une quantité importante d'organismes étrangers, environ un milliard par nodosité. La colonisation bactérienne massive des nodosités est permise grâce à la suppression des réponses immunes de la plante. Les racines sont en contact avec l'abondante flore microbienne du sol, ce qui soulève la question des conséquences liées à la potentielle vulnérabilité des organes symbiotiques ainsi que les plantes nodulées. L'objectif du projet de thèse était d'évaluer la vulnérabilité des organes symbiotiques. Pour cela, nous avons mis en place deux systèmes tripartites impliquant la légumineuse-modèle, Medicago truncatula, son symbionte, Sinorhizobium medicae et séparément deux microorganismes phytopathogènes, une bactérie Ralstonia solancearum et un champignon Sclerotinia sclerotiorum. Nous avons aussi caractérisé les réponses des nodosités face à ces deux pathogènes et cela en prenant les racines comme référence. Enfin, nous avons estimé l'influence de la nodulation et de la fixation d'azote sur la vulnérabilité des plantes face à l'agent pathogène bactérien. Les travaux effectués durant les trois ans de thèse indiquent que les nodosités sont des sites d'infection pour les agents pathogènes et qu'elles sont capables de répondre à la présence de pathogènes, néanmoins de manière différente et plus faiblement que les racines. Les résultats obtenus en utilisant l'un de nos systèmes tripartites suggèrent que la nodulation et la fixation d'azote peuvent conférer une plus grande sensibilité face aux agents pathogènesNitrogen is essential element for the development of all living beings. Although it is found in large quantity in the air, in the form of dinitrogen, it is not directly assimilable by most organisms. For example, plants are not able to assimilate this form. However, in a nitrogen deficient environment, legumes are able to interact with soil borne bacteria, rhizobia, which fix nitrogen thanks to an enzymatic complex, the nitrogenase. Indeed, bacteria reduce dinitrogen in ammonium; plants can assimilate this form. Plants host these bacteria in particular organs at the root level, the nodules, where they provide nutrients to bacteria. Plant tolerates in its own cells a tremendous quantity of foreign organisms, estimated to one billion of rhizobia per nodule. The massive bacterial colonization of nodules is allowed thanks to the repression of plant immunity. Roots are in contact with the abundant soil microbiota, which raises the question of the potential vulnerability of the symbiotic organs and nodulated plants. The phD project aimed to evaluate the nodules vulnerability. To achieve this, we set up two tripartite systems involving the model legume, Medicago truncatula, its symbiont, Sinorhizobium medicae and separately two phytopathogenic microorganisms, a bacterium, Ralstonia solancearum and the fungus, Sclerotinia sclerotiorum. We also characterized nodules responses to both pathogens using roots as reference. Finally, we estimated the influence of nodulation and nitrogen fixation on the plant vulnerability to pathogens. Work performed during these three years indicates that nodules are infection sites for pathogens. Those nodules are able to perceive the pathogen however, their response is different and less intense than that of roots. Results obtained with one of our tripartite system suggest that nodulation and nitrogen fixation give a greater sensitivity to pathogens
26
Chafchaouni-Bussy, Moussaoui Imane. "Etude de l’implication des lipopolysaccharides dans la Symbiose Bactérie-Plante productrice d’azote." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA11T045.
Abstract:
Nous nous sommes intéressés à la compréhension des mécanismes régissant la symbiose Rhizobium-Acacia dans les conditions de stress salin. Les lipopolysaccharides jouent un rôle important dans les étapes de cette symbiose. Le but était de mettre en évidence les modifications pariétales de la bactérie en réponse au stress salin par l’étude de la structure des lipopolysaccharides des souches isolées du désert marocain tolérant NaCl 7%. Ainsi, une nouvelle méthode d’hydrolyse des lipopolysaccharides sensible, non destructive et compatible avec la spectrométrie de masse a été développée. En présence de stress salin, nous avons montré que la membrane externe devenait plus hydrophobe en augmentant l’acylation de la région lipidique ainsi qu’en réduisant la présence des molécules de LPSs à longues chaînes de sucres.Des essais d’évaluation de l’efficience et de l’infectivité des Rhizobia étudiés ont été mis en œuvre pour déterminer l’impact de ces modifications des LPSs sur la symbiose sous stress salinWe were interested in the understanding of the mechanisms governing Rhizobium-Acacia symbiosis in salt stress conditions. Lipopolysaccharides play an important role in the stages of this symbiosis. The aim of this work was to highlight the changes occurring in the bacterial membrane in response to salt stress by studying the structure of the lipopolysaccharides isolated from Moroccan desert strains tolerating 7% NaCl. Thus, a new method of hydrolysis of the lipopolysaccharide - sensitive, non-destructive and compatible with mass spectrometry- was developed. We studied the LPSs strains grown with or without salt stress and we showed that in salt stress conditions, the outer membrane becomes more hydrophobic by increasing acylation of the lipid region and reducing the number of long sugar chains in LPSs. Tests for evaluating the efficiency and infectivity of the studied rhizobia were carried out to determine the impact of these LPS modifications on symbiosis under salt stress
27
Abdul, Jalil A. I. "The growth and colonisation of rhizobia on mycorrhizal Trifolium repens (L.)." Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370869.
28
Alexandre, Ana, and Solange Oliveira. "Heat shock response in bacteria with large genomes: lessons from rhizobia." Bachelor's thesis, Wiley-Blackwell Publishers, 2016. http://hdl.handle.net/10174/19210.
Abstract:
Rhizobia are important soil bacteria due to their ability to establish nitrogen-fixing symbioses with legume plants. In this dual lifestyle, as free-living bacteria or as plant symbiont, rhizobia are often exposed to different environmental stresses. The present chapter overviews the current knowledge on the heat shock response of rhizobia, highlighting how these large genome bacteria respond to heat from a transcriptional point of view.
Response to heat shock in rhizobia involves genome wide changes in the transcriptome that may affect more than 30% of the genome and involve all replicons. In addition to the expected upregulation of genes already known to be involved in stress response (dnaK, groEL, ibpA, clpB), the reports on the heat shock response in rhizobia also showed particular aspects of stress response in these resourceful bacteria. The transcriptional response to heat in rhizobia includes the overexpression of a large number of genes involved in transcription and carbohydrate transport and metabolism. Additional studies are needed in order to better understand the transcriptional regulation of stress response in bacteria with large genomes.
29
Troyee, Anupoma Niloya. "Impact of soil treatments in the conservation of native rhizobia populations." Master's thesis, Universidade de Évora, 2017. http://hdl.handle.net/10174/22076.
Abstract:
Sustainable agriculture aims to achieve highcrop production, reducing the use of chemical fertilizers and herbicides. Rhizobia-legume symbioses are importantN2-fixing systems that can improvethe productivity ofsoils.The aim of this work was toevaluate the diversity of rhizobia on nodules of chickpeaplants grown in soil treated with a glyphosate, nitrate and Mesorhizobiuminoculation. The impact of glyphosate and nitrate on mesorhizobia growth and on the early stages of infection was also evaluated. The phylogenetic analysis of the 16S rRNA gene sequences showed a low diversity of rhizobia nodulating chickpea, regardless of the treatments applied. The detection of Mesorhizobiummuleiense as predominant species may be related to the high competitiveness of this species. Smallerroot hairsand less curling was observed for the highestconcentrations ofnitrate tested. This work hascontributed to clarifythe impact of chemical fertilizers and herbicide application onthe legume-rhizobia symbiosis; Impacto de tratamentos do solo na conservação das populações nativasde rizóbio
Sumário:
A agricultura sustentável tem como objetivo atingir elevadas produções, reduzindo o uso de fertilizantes químicos e herbicidas. As simbioses rizóbio-leguminosa são importantes sistemas de fixação de N2,que podem melhorar a produtividade dos solos. O objetivo deste trabalho foi avaliar a diversidade de rizóbios nos nódulos de grão-de-bico plantado em solo tratado com glifosato, nitrato e inoculação de Mesorhizobium. Um outro objetivo foi a avaliação do impacto do glifosato e nitrato no crescimento de rizóbios e nas fases iniciais da infeção. A análise filogenética das sequências do gene 16S rRNA mostrou uma baixa diversidade de rizóbios em nódulos de grão-de-bico, independentemente do tratamento. A deteção de Mesorhizobium muleiensecomo espécie predominante poderá estar relacionada com elevada competitividade desta espécie. Pêlos radiculares mais pequenos e menos “curling” foram observados para as concentrações mais elevadas de nitrato testadas. Este trabalho contribuiu para clarificar o impacto de fertilizantes e herbicidas nesta simbiose.
30
Salo, Lucinda Faith. "COMPETITION BETWEEN STRAINS OF RHIZOBIA FOR NODULATION OF LEUCAENA LEUCOCEPHALA (LEGUME)." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275326.
31
Sublett, Jacob D. "Effects of seed coat variation and population on plant-microbial interactions." Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1467569697.
32
Hsu, Chiun-Kang. "EVALUATION OF SEED TREATMENTS ON THE NODULE COMPETENCY OF SOYBEAN INOCULANTS." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/dissertations/823.
Abstract:
Soybean has a strong demand for nitrogen that can be acquired from atmosphere for vegetative growth and seed production through the symbiosis with the soil bacterium Bradyrhizobium japonicum (B. japonicum). However, the native soil bradyrhizobia may be ineffective in nitrogen fixation and the greatest limiting factor in increasing symbiotic nitrogen fixation is the inability to influence the infection of soybean roots by a desired strain of B. japonicum due to competition from the native bradyrhizobia. Previous studies have demonstrated the efficacy of a co-inoculum seed treatment on the symbiotic competency of the soybean cultivar LS90-1920 in greenhouse and field trials. The co-inoculation by the soil bacterium Streptomyces kanamyceticus (S. kanamyceticus) strain ATCC 12853 and strains of B. japonicum more efficient in nitrogen fixation and resistant to the antibiotics kanamycin and neomycin may have an advantage over the native bradyrhizobia regarding soybean root infection (Gregor et al., 2003). However, inconsistent inoculation responses in field trials and low efficacy in nodule competency by selected Bradyrhizobium japonicum (B. japonicum) co-inocula were observed under greenhouse conditions. These results were attributed to insufficient population size or growth of viable co-inocula associated with the seed treatments. This recent study showed that the nodulation response of LS90-1920 to B. japonicum strains KNI-1 and KNI-3 is independent of the inoculum dose and age of the broth culture. Iron supplement to the inoculum nutrient solution significantly increased the total biomass of nodules formed by strain KNI-1 but not by strain KNI-3 on a per plant basis and had no effect on the nodule number regardless of B. japonicum strain. In the glass bead viability study, the effect of inoculum nutrient solution concentration on the viability of bacterial co-inocula is species-specific and influenced by seed coating material. The growth of Pseudomonas putida strains displayed a dependency on the concentration of the inoculum nutrient solution with graphite or vermicompost as the seed coating material treatment or with activated charcoal treatment associated with 0.1% or 1.0 % inoculum nutrient solution. The seed coating material treatments of vermicompost and graphite promote stronger growth of S. kanamyceticus strain ATCC 12853 than the activated charcoal treatment. After a six-day incubation at 28oC, a 1.0 % inoculum nutrient solution maintained the highest viable populations of co-inocula with activated charcoal and a 0.1% inoculum nutrient solution was most effective in the maintenance of the co-inocula population when graphite or vermicompost was employed as the seed coating material. By applying the appropriate level of inoculum nutrient solution, the viability of a selected B. japonicum KNI strain and co-inocula remained stable for six days in activated charcoal and graphite treatment regardless of the number of applied co-inocula. However, the vermicompost treatment did not maintain the viable populations of the B. japonicum KNI strains and P. putida strain G11-32 but support the vigorous growth of S. kanamyceticus strain ATCC 12853 and P. putida strain 17-29. Greenhouse studies employing sterilized vermiculite as a soybean growth medium showed no significant differences in nodule competency by the inoculum/seed coating treatments associated with B. japonicum strain KNI-1. However, the co-inoculum treatments significantly increased either the total nitrogenase activity (B. japonicum strain KNI-3 with S. kanamyceticus strain ATCC 12853) or the nodule number (B. japonicum strain KNI-3 with S. kanamyceticus strain ATCC 12853 and P. putida strain 17-29) versus the singular inoculum treatment of strain KNI-3. Soil-pot studies under the same greenhouse conditions showed no significant differences in the nodule competency between the inoculum treatment of B. japonicum strain KNI-3, the co-inoculum treatment of strain KNI-3 and S. kanamyceticus, and the non-inoculated control regardless of seed coating material. However, co-inoculation of emergence-promoting rhizobacteria (Pseudomonas putida strain 17-29 and G11-32) with strain KNI-3 and S. kanamyceticus strain ATCC 12853 may improve the total nitrogenase activity and specific nitrogenase activity, depending on the seed coating material and soil type. The treatment with activated charcoal employed as a seed coating material and the co-inocula of strain KNI-3, S. kanamyceticus strain ATCC 12853 and P. putida strains 17-29 or G11-32 showed significantly higher total nitrogenase activity (Stoy silt loam) and specific nitrogenase activity (Drummer silty clay loam) versus the non-inoculated control. For the Bethalto silty clay loam, the same co-inoculum treatment associated with graphite and vermicompost as the seed coating material significantly increased the total nitrogenase activity. The seed coating treatment by activated charcoal enhanced nodulation competency for both the 2010 and 2011 field trials resulting in higher grain yield, seed nitrogen content, and seed protein content versus the seed coating treatment by graphite. No significant differences by the inoculum treatments were determined.
33
Bala, Abdullahi. "Biodiversity of rhizobia which nodulate fast-growing tree legumes in tropical soils." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391891.
34
Bontemps, Cyril. "Exploration et analyse de la diversité des rhizobia : nouveaux outils et concepts." Lyon 1, 2005. http://www.theses.fr/2005LYO10224.
Abstract:
Suite à l'identification de β-protéobactéries nodulantes, nous avons confirmé le statut symbiotique de ces nouveaux rhizobia. R. Taiwanensis LMG19424 a été choisi et caractérisé comme β-rhizobium modèle en vue du séquençage de son génome. Afin d'explorer davantage leur diversité, nous avons développé une méthode moléculaire d'identification des rhizobia qui s'affranchit des tests de nodulation en laboratoire. Grâce à une approche innovante par puce à ADN, utilisant comme sondes des motifs conservés de nodC et l'hybridation croisée d'une cible avec plusieurs sondes, nous avons pu détecter la présence de ce gène dans des cultures bactériennes ou des échantillons végétaux (nodules), évitant ainsi l'étape d'isolement du symbionte. L'analyse par clustering hiérarchisé des patterns d'hybridation permet également d'apporter une information phylogénétique sur le gène détecté. Cette approche originale et rapide est applicable à la détection d'autres gènes et fonctions bactériennes d'intérêt
35
Sangay-Tucto, Sheena. "Étude de l’impact des symbioses mycorhizienne et rhizobienne dans la domestication du Tara, Caesalpinia spinosa L." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG080/document.
Abstract:
La Tara (Caesalpinia spinosa) est une espèce forestière d’une grande importance en raison d’une forte demande sur le marché international pour les tanins présents dans ses gousses, et pour les gommes provenant de ses graines. Malgré son importance économique pour le Pérou, la majeure partie de la production provient de forêts naturelles non aménagées. Ces forêts présentent des problèmes de sol (érosion, faible fertilité, présence d’agents pathogènes, manque d'irrigation), qui conduisent à des rendements faibles. C’est pourquoi dans le présent travail, nous étudions les composantes microbiologiques du sol associé à cette culture, telles que les mycorhizes et les bactéries dont l’utilisation, selon de nombreuses études, s’est révélée être une alternative à l'utilisation d'engrais chimiques. Pour cela, nous avons procédé à l'analyse moléculaire de la diversité des champignons mycorhiziens arbusculaires par la technique de Miseq Illumina, ce qui nous a permis de mettre en évidence une prépondérance de Gloméracées parmi lesquelles les Rhizophagus spp. étaient retrouvés dans 70% des séquences. En outre, la dépendance de la Tara vis-à-vis de la mycorhization a été démontrée car, après avoir testé la mycorhization contrôlée de la Tara par Rhizophagus irregularis, il a été constaté que la croissance de Caesalpinia spinosa était considérablement améliorée, ainsi que l'absorption d'éléments nutritifs tels que l'azote (N) et le phosphore (P). Pour vérifier la capacité à noduler de la Tara, différents milieux de culture ont été utilisés ainsi que différentes conditions de croissance, en serre et in vitro. Ces expérimentations ont toutes montré que les racines de Tara ne présentaient pas de nodules, confirmant que cette légumineuse de la sous-famille des Caesalpinioideae est non nodulante. Par conséquent et afin d’étudier la diversité des rhizobia présents dans le sol de la plantation de Tara, nous avons utilisé en serre une plante-piège, le pois (Pisum sativum) car c’est une légumineuse nodulante et de plus est traditionnellement associée à la culture de Tara. Les rhizobia identifiés moléculairement se sont révélés très spécifiques et différents des rhizobia présents dans les sols extérieurs à la plantation de Tara. Plus particulièrement, ces rhizobia se sont révélés être phylogénétiquement proches de R. etli, R. phaseoli, R. pisi et R. leguminosarum. Enfin, un test d'inoculation contrôlée (in vitro) a été réalisé sur des plantules de pois, avec ces bactéries préalablement piégées et isolées du pois. Il a été observé que les rhizobia piégés à partir des sols collectés entre deux lignes de Tara et sur la ligne de plantation de Tara, ont stimulé la croissance du pois par rapport aux rhizobia présents dans les sols collectés à l'extérieur de la plantationThe Tara (Caesalpinia spinosa) is a forest species of great importance due to its high demand in the international market for the tannins present in its pods and its seeds’ gum. Despite its great importance for Peru, most of the production comes from unmanaged natural forests. These forests present soil problems (e.g., erosion, low fertility, pathogens, lack of irrigation), which cause low yields. Therefore, in the present work we seek to study the soil components associated with Tara plantation , such as mycorrhizae and bacteria that have proved to be an alternative for reducing the use of chemical fertilizers in similar context (Aboubacar et al., Flores Chavez 20015, E and Saif 1987, Dia et al. 2010; Bilgo et al., 2013) . We used molecular analysis of the arbuscular diversity by the Miseq Illumina technique that allowed to verify the arbuscular diversity with a preponderance of Glomeraceae among which the Rhizophagus spp were found to be present in 70% of the sequences. In addition, the dependence of the Tara on obligatory mycorrhization was demonstrated, after testing the controlled mycorrhization of the Tara by the Rhizophagus irregularis. We found that the growth of this crop was significantly improved, as well as the absorption of nutrients such as nitrogen (N) and phosphorus (P).To check the nodulation of the Tara, different culture media were used (JenSen, sand mixture with Tara plantation soil, attapulgite mixture with Tara plantation soils) in greenhouse and in vitro condition. We did not manage to find rhizobial nodules in the roots which let us think that Tara is a non-nodular legume. Therefore, we used Pisum sativum as a trap plant to study the diversity of rhizobia present in the soil of the Tara plantation since this legume is often associated with Tara crop. The rhizobia found in the trap plant were very specific and different from the rhizobia present in soils outside the Tara plantation. Likewise, these rhizobia found to be phylogenetically close to R. etli, R. phaseoli, R. pisi and R. leguminosarum. Finally, we inoculated the trapped bacterias (in vitro) in Pisum sativum with the bacterias previously trapped and isolated from the pea (which grew in the green house); where it was observed that the rhizospheric bacteria of the zones IL (soil collected between two lines) and L (soil collected from the same line) from the plantation of Tara stimulated the growth of this crop with respect to the bacteria present in soils collected outside of the plantation (OP zone)
36
Miller, Simon Hugh, and n/a. "Genetic basis for the host-specific nitrogen fixation phenotype of Caucasian clover rhizobia." University of Otago. Department of Microbiology, 2006. http://adt.otago.ac.nz./public/adt-NZDU20070306.155157.
Abstract:
Trifolium ambiguum (Caucasian clover) is being released in New Zealand for use in areas where growth of T. repens (white clover) is marginal. Although closely related to T. repens, T. ambiguum has unique and highly specific nodulation requirements and as rhizobial strains capable of effectively nodulating T. ambiguum are not naturally found in New Zealand soils, they must be introduced with the seed. Rhizobium leguminosarum bv. trifolii strains such as ICC105 form effective nodules on T. ambiguum but ineffective (Fix⁻) nodules on T. repens. The T. repens nodules nevertheless develop normally and contain bacteroids. R. l. bv. trifolii strains that are effective on T. repens such as NZP561, fail to nodulate T. ambiguum. As the host-specific nitrogen fixation defect of Caucasian clover rhizobia on T. repens has potentially adverse agronomic implications, the genetic basis for this Fix⁻ phenotype was investigated.
Rhizobium leguminosarum bv. trifolii strain ICC105 was converted to Fix⁺ on T. repens by the introduction of an 18-kb fragment of DNA from a white clover rhizobial strain (NZP514) symbiotic plasmid. This fragment contained several nif and fix genes, including nifHDKEN, fixABCX, nifA, nifB, fdxN and fixU. Tn5 mutation of these white clover rhizobial genes demonstrated that most were required to impart the Fix⁺ phenotype on T. repens to ICC105, with the exception of nifA. Mutagenesis of the ICC105 nifA gene and subsequent complementation with various combinations of the white clover rhizobia nif/fix genes as well as transcriptional lacZ fusion studies of the ICC105 nifA and nifH genes demonstrated that ICC105 nifA is expressed and functional during the ineffective nodulation of T. repens and able to activate expression of nifHDKEN and fixABCX operons derived from white clover rhizobium but not from ICC105.
Sequence analysis and comparison of the intergenic region between the divergently transcribed nif/fix operons revealed a conserved 111-bp region found between the nifH/fixA promoters of Caucasian clover rhizobia, but not in white clover rhizobia. Attempts to modify this region in ICC105 failed in creating a strain which was Fix⁺ on T. repens; however recombination of the nifHD/fixAB region from a white clover rhizobium into the ICC105 genome produced several strains with a �swapped� nitrogen fixation phenotype (i.e. Fix⁺ on T. repens and Fix⁻ on T. ambiguum). A hypothesis was therefore proposed by which differences in the nifH/fixA promoter regions of Caucasian clover rhizobia and white clover rhizobia modulate the expression of the upstream genes in response to the particular plant host they are nodulating.
The incompatibility between the symbiotic plasmid of R. l. bv. trifolii ICC105 and the white clover rhizobium symbiotic plasmid cointegrate, pPN1, was also investigated and potential regions of each plasmid involved in this incompatibility were identified.
The research presented in this thesis has contributed to the genetic knowledge of the nitrogen fixation genes, and regulation of these genes in R. l. bv. trifolii. It has also provided progress towards the goal of creating a suitable inoculant strain for T. ambiguum that is able to fix nitrogen in symbiosis with both T. repens and T. ambiguum.
37
O'Callaghan, Kenneth John. "Interactions of rhizobia with Sesbania rostrata, wheat and oilseed rape : a comparative study." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285558.
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Spriggs, AC, and FD Dakora. "Symbiotic performance of selected Cyclopia Vent. (honeybush) rhizobia under nursery and field conditions." Symbiosis, 2009. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001479.
Abstract:
Abstract
Three newly selected strains of Cyclopia rhizobia together with an inoculant strain, which has never been tested in the field
with adequate experimental design, was assessed under both nursery and field conditions for symbiotic performance. The
three new test strains were initially selected for their superior Nz-fixing abilities under glasshouse conditions, and then
evaluated in this study for field performance. Cyclopia subternata Vogel and Cyclopia genistoides (L.) R. Br., which have
the potential for producing high quality honeybushtea, were used as host plants in both the nursery and field studies.The
effect of seedling inoculation at the nursery level was also examined for the four test strains under nursery conditions. The
inoculation of cuttings under nursery conditions produced.significant increases in shoot biomass, shoot %N and shoot N
content. More specifically, inoculating C. subternata with strains UCT44b and UCT61a significantly increased shoot
biomass and N content relative to strain PPRICI3. Strains UCT44b and UCT61a also showed better nodulation with
C. subternata cuttings compared to strains UCHOa and PPRICI3. Field inoculation of Cyclopia increased all growth
parameters relative to the uninoculated control, except for leaf %N. Cyclopia subternata inoculated with strains UCT44b,
UCT40a and UCT61a produced significantly lower b15N values than the uninoculatedC. subternata reference plant. Using
the 15N natural abundance method, C. subternata was estimated to be gaining about half of its N from Nz fixation, while
C. genistoides obtained less than half of itsN from symbioticnutrition.
39
Shamsuddin, Zulkifli Haji. "Growth, infectivity and nodulating abilities of some winged bean rhizobia in acid conditions." Thesis, Shamsuddin, Zulkifli Haji (1987) Growth, infectivity and nodulating abilities of some winged bean rhizobia in acid conditions. PhD thesis, Murdoch University, 1987. https://researchrepository.murdoch.edu.au/id/eprint/51958/.
Abstract:
The present research project was undertaken to study the growth of winged bean and its rhizobia, the infectivity and nodulating abilities of winged bean rhizobia, and the symbiotic growth of winged bean, in acid conditions. The effects of different carbon and nitrogen sources and the rhizosphere on growth of rhizobia and final pH of media were also investigated.
Three winged bean cultivars behaved similarly in the response of their top dry matter to soil treatments which increased acidity: they differed in their root responses.
Fifty-two Bradyrhizobium strains from nine international research centres were found to nodulate winged bean and their effectiveness assessed. Forty-one effective strains were screened for growth in acid conditions, using two different techniques.
In soils without plant roots, CB756 began to show a lag phase but could grow at pH 4.4 (1:5 in 0.01 M CaCl2); NRll 2 produced no growth even at pH 4.6. The presence of winged bean roots reduced the rhizobial growth limitations due to the combined effects of low pH (4.4) and addition of aluminium (0.33 -1 cmol (+) kg-1 soil).
The combined effect of low pH (4.4) and aluminium -1 application (0.33 cmol (+)kg-1 soil) reduced nodulation and total nitrogenase activity in winged bean cv. TPtl inoculated with CB756. For NRll, which is unable to grow in acid soil at pH 4.6, a similar reduction occurred at the higher pH (4.6), a trend which directly reflects the influence of survival of rhizobia on nodule number and dry weight, and nitrogenase activity. Growth of TPtl, a cultivar tolerant of acid soil at pH 4.4 when supplied with inorganic nitrogen, was reduced at pH 4.4 and 4.6, when inoculated with CB756 and NRll, respectively.
These results suggest that in the winged bean -Bradyrhizobium symbiosis under acid conditions, the growth of rhizobia and the processes of nodulation and nitrogen fixation are both limited by low pH; these limitations are greater than that on growth of the host-plant. The limitations to nodulation and total nitrogen fixed vary inversely with the acid tolerance of the rhizobia. Acid-tolerant strains formed nodules earlier and fixed nitrogen sooner than acid-intolerant strains.
40
Godschalx, Adrienne Louise. "Symbiosis with Nitrogen-fixing Rhizobia Influences Plant Defense Strategy and Plant-predator Interactions." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3644.
Abstract:
As sessile organisms, plants evolved a plethora of defenses against their attackers. Given the role of plants as a primary food source for many organisms, plant defense has important implications for community ecology. Surprisingly, despite the potential to alter entire food webs and communities, the factors determining plant investment in defense are not well-understood, and are even less understood considering the numerous symbiotic interactions in the same plant. Legume-rhizobia symbioses engineer ecosystems by fixing nitrogen from the atmosphere in trade for plant photosynthates, yet connecting symbiotic resource exchange to food web interactions has yet to be established. Here I test how rhizobia influence plant defense and tritrophic interactions in lima bean (Fabaceae - Phaseolus lunatus L.): a model plant in chemical ecology research characterized by a broad range of different defenses. Examining suites of traits among lima bean genotypes, highly cyanogenic cultivars and wild type plants (high cyanotypes) produce more hook-shaped trichomes, as a putative combined approach of chemical and mechanical defenses, forming defense syndromes to protect against multiple feeding guilds (Chapter 2). Testing costs that may have contributed to forming tradeoffs among strategies, high cyanotypes show reduced fitness under plant-plant competition relative to low cyanotypes, but when challenged with herbivory, high cyanotypes fitness reductions are no longer evident (Chapter 3). Young leaves, not reproductive organs, are the most cyanogenic lima bean organ, and removal quantitatively decreases fitness, supporting assumptions that the most valuable tissues will be most highly defended (Chapter 4). Testing the degree to which nitrogen-fixing rhizobia contribute to cyanogenesis, high cyanotypes form more nodules than low cyanotypes. Quantitative relationships between nodule number and plant traits highlight the role symbiotic investment plays a role in plant defense and nutritive phenotype, while simultaneously, genotypically-determined levels of defense shape plant investment in symbiosis (Chapter 5). Interestingly, traits that trade off by cyanotype (i.e. high cyanogenesis but low indirect defense) reflect the patterns in plants with nitrogen-fixing rhizobia. Rhizobia-inoculated lima beans show reduced indirect defenses, recruiting fewer parasitoid wasps (Chapter 6) and predatory ants (Chapter 7). Examining plant-ant attraction in greater detail, ants prefer headspace regions above EFN droplets, corresponding with species-specific differences in suites of volatiles, indicating EFN, like floral nectar, can be scented to manipulate insect behavior (Chapter 8). Overall, understanding when investing in traits to recruit predators is more effective than investing in defensive chemistry, and how particular ecological contexts, such as symbioses can influence the outcome of defense allocation strategies remains a fascinating area of research. Determining the mechanisms underlying why rhizobia and other belowground microbial symbionts influence their host plants' above ground interactions, whether plants traits affected by symbiotic microbes are simply a function of the costs and benefits from resource exchange, or whether symbionts can influence the success of primarily direct versus indirectly defended plants is an important question for understanding complex trophic systems and connecting to agricultural implications for more effective biological pest control.
41
Otieno, Mary Atieno. "Proteomic Changes in Rhizobia after Growth in Peat Extract and Their Potential Role in Desiccation Tolerance." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17791.
Abstract:
Survival of rhizobia on seed is mainly affected by desiccation. Inherent differences in survival exist between rhizobia strains as well as with growth conditions, with a general improvement in survival seen in cells grown in peat over cells grown on growth media. Improving survival of rhizobia under desiccation stress may enhance nitrogen fixation and crop yields. This study aimed to relate desiccation tolerance of rhizobia to physiological changes in cells grown in peat extract. Survival of four rhizobia strains (Rhizobium leguminosarum bv. viciae, 3841, Rhizobium leguminosarum bv. trifolli TA1, Bradyrhizobium japonicum, CB1809, Bradyrhizobium diazoefficiens sp. nov.) was measured after growth in peat extract. This study reported an improvement in survival of Bradyrhizobium strains USDA110 and CB1809 compared to the Rhizobium strains 3841 and TA1. The global proteomic responses of the four rhizobia strains after growth in peat extract was compared with defined medium JMM. Differentially expressed proteins were reported across the four strains with a possible role in desiccation tolerance such as ABC transporters, stress response, transcription, translation and oxidative stress proteins. The role of one protein, PspA (RL3579), was validated by creating a knock-out mutant. The RL3579 mutant grown in peat extract reported significantly lower percentage survival of 2% as compared to the wild-type (5.3%), and could be attributed to loss in membrane integrity. This study confirms that survival of rhizobia can be improved after growth in peat extract, due to stress-related proteins that may function in protecting cells from desiccation-induced damage. The roles of these stress proteins and effect of specific components of peat could be manipulated to develop desiccation-tolerant strains and inform development of new inoculant carriers for legume inoculation.
42
Maghraoui, Tasnime. "Diversité génotypique et fonctionnelle des rhizobia associés aux cultures mixtes Fève-Blé en conditions limitantes de phosphore au Maroc." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT147.
Abstract:
Cette étude a pour principal objectif de mettre en évidence le rôle des bactéries solubilisatrices de phosphate (rhizobia) dans une meilleure gestion des systèmes de cultures associant la fève (légumineuse) et le blé (céréale) en monoculture et en cultures mixtes sous des conditions de déficience en P. Cent neuf souches de rhizobia ont été isolées à partir des nodules racinaires des plantes de V. faba dans la région de Marrakech. Les analyses phylogénétiques basées sur les gènes 16S rDNA, recA et nodD montrent que les souches étudiées sont proches phylogénétiquement de R. leguminosarum biovar viciae, de R. laguerreae et de Ensifer meliloti. Nous avons également décelé la présence du gène pqqC qui est impliqué dans la solubilisation du phosphate (pyrroloquinoline quinone synthase C) chez 15 souches de rhizobia. 22% de ces souches ont été identifiées comme étant capables de solubiliser le phosphate minéral. Ensuite, nous avons montré que l’inoculation avec certaines souches de rhizobia ayant la capacité de solubiliser le P in vitro améliore la croissance des plants de fève et de blé en serre (en monoculture et culture mixte). Nous avons aussi noté des réponses différentes à l’effet de l’inoculation selon les combinaisons symbiotiques étudiées fève-rhizobia. Nous avons également montré que les souches de rhizobia peuvent stimuler le transfert d'azote fixé de la fève au blé, ce qui pourrait contribuer de manière significative au processus de facilitation plante-plante dans les cultures en association dans des conditions de sols carencés en phosphore. En plus de ces avantages de l’association, cette pratique culturale n’est pas limitée à un effet trophique (amélioration de la nutrition azotée des plantes), mais pourrait résulter d'interactions microbiennes qui peuvent agir directement sur la croissance du blé (effet PGPR). Les résultats des expérimentations menées en serre et au champ montrent, en effet, que les cultures mixtes stimulent la croissance du blé ainsi que sa nutrition minérale (N et P).Ces résultats soulignent l'utilité de développer ce type de pratiques culturales associant les légumineuses et les céréales et d'utiliser les ressources microbiennes locales dans les agro-écosystèmes afin d’améliorer la production agricole, en réduisant l’utilisation des intrants chimiques coûteux et néfastes pour l'environnementThe main purpose of this study is to evaluate the role of phosphate solubilizing rhizobial strains in promoting faba bean (legume) and wheat (cereal) growth in mono and mixed cultures under phosphorus deficiency conditions. 109 rhizobial strains have been isolated from nodules of V. faba plants in Marrakech region. Phylogenetic analysis based on 16S rDNA, recA and nodD genes showed that the studied strains are close to Rhizobium leguminosarum biovar viciae, R. laguerreae and Ensifer meliloti. We detected the presence of pqqC gene which is implicated on phosphate solubilization (Pyrroloquinoline-quinone synthase C) in 15 rhizobia strains. 22 % of isolated strains were found to be able to solubilize mineral phosphate. We have demonstrated that the inoculation with some of rhizobial strains with PSolubilization capacity in vitro, improved the growth of fava bean and wheat plants in greenhouse (both in mono and mixed cultures). We noticed different reactions to the inoculation's effect, depending on the symbiotic combinations faba bean-rhizobia studied. We also showed that rhizobial strains can stimulate the transfer of fixed nitrogen from the bean to the wheat, which could contribute significantly to the plant-plant facilitation process in associated cultures with phosphorus deficiency conditions. Besides this association advantages, this cultural practice is not limited to a trophic effect (improvement of the nitrogenous nutrition of plants), but could engender microbial interactions which can directly enhance the wheat growth (PGPR effect). The results of the experiments conducted in greenhouse and on field show that mixed cultures stimulate wheat growth and its mineral nutrition (N and P). These results underline the utility of developing this kind of cultural practices associating legumes and cereals, and to use the local microbial resources in the agro-ecosystems to improve the agricultural production by reducing the use of agricultural improvers among others expensive artificial fertilizers which represent a threat to the environment
43
Melkonian, Rémy. "Etude de la spécificité d’association béta-rhizobia-Mimosa : approches par l'écologie microbienne et la génomique fonctionnelle." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20195/document.
Abstract:
Les béta-rhizobia sont des symbiotes de légumineuses retrouvées principalement associés au genre Mimosa. Les études des symbiotes de Mimosa pudica révèlent différents profils de diversité au sein des alpha (Rhizobium spp) et béta-rhizobia (Burkholderia, Cupriavidus) le long de la ceinture tropicale, les béta-rhizobia étaient toujours majoritaires dans les nodosités de cette plante hôte. Dans ce travail de thèse, nous avons étudié cette spécificité d'association béta-rhizobia/Mimosa pudica, par une approche couplant l'étude des traits symbiotiques bactériens à l'analyse des profils d'expression de leurs génomes dans les premières étapes de la symbiose, et en comparaison avec les alpha-rhizobia. Nous avons analysé les traits symbiotiques (compétitivité pour la nodulation, efficience symbiotique) au niveau intra et interspécifique de 4 espèces de béta-rhizobia et 4 d'alpha-rhizobia. Si l'efficience symbiotique est similaire parmi toutes les souches testées, différents niveaux de compétitivité ont été trouvés selon l'espèce, B. phymatum et B. tuberum étant les plus compétitives. Les tests effectués sur différentes variétés de M. pudica montrent un effet variétal sur la compétitivité de C. taiwanensis. Les traits symbiotiques mesurés expliquent en partie les profils de diversité des symbiotes de M. pudica dans les zones d'origine (Amérique du Sud) ou en zone introduite (Taiwan). Les transcriptomes de trois bactéries ayant des traits symbiotiques différents (B. phymatum STM815, C. taiwanensis LMG19424 et R. mesoamericanum STM3625) ont été comparés (par RNAseq), pour relier les différentes réponses induites par les exsudats racinaires aux traits symbiotiques de chaque rhizobium. Chaque bactérie développe une stratégie spécifique liée à ses traits symbiotiques et à l'origine de la symbiose dans son groupe bactérienBeta-rhizobia are legume symbionts mainly found associated to the Mimosa genus. Diversity studies of Mimosa pudica symbionts in native and introduced areas reveal different diversity patterns of alpha (Rhizobium spp) and beta-rhizobia (Burkholderia, Cupriavidus), with beta-rhizobia being always the main symbionts in the nodules of this legumes species. In this thesis we have studied the symbiotic specificity between beta-rhizobia and M. pudica (and the comparison with alpha-rhizobia) by a dual approach combining the study of bacterial symbiotic traits and the analysis of their transcriptomes in the first steps of symbiosis. We analysed symbiotic traits (nodulation competitiveness, symbiotic efficiency) at intra and interspecific levels on four species of beta-rhizobia and four of alpha-rhizobia. If symbiotic efficiency is similar among all strains, different levels of competitiveness were measured with a strong strain effect largely explained by the species affiliation, B. phymatum and B. tuberum being the most competitive species. Tests on different M. pudica varieties showed an impact on the competitiveness of C. taiwanensis. Symbiotic traits explained in part the symbiont patterns observed in diversity studies in French Guiana (M. pudica native area) and Taiwan (introduced). Root-exudates induced transcriptomes of three bacteria (two beta--rhizobia: B. phymatum STM815, C. taiwanensis LMG19424 and one alpha, R. mesoamericanum STM3625) with contrasted symbiotic traits were compared (by RNAseq). Each bacterium develops a specific strategy linked to its symbiotic traits and the origin of symbiosis in its bacterial group
44
Domergue, Odile. "Diversité fonctionnelle des rhizobia associés à la féverole en agro-écosystème Sud de France." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEP067/document.
Abstract:
L’aptitude des symbioses rhizobium-légumineuses à fixer l’azote atmosphérique, peut offrir d’importants services aux agro-écosystèmes. Cependant, associés à des contraintes biotiques (i) absence et/ou (ii) inefficacité symbiotique des rhizobiums du sol, des facteurs abiotiques (i) excès d’intrants azotés et/ou (ii) carences en phosphore (P) peuvent limiter la fixation symbiotique d’azote (FSN). Le Myo-inositol hexakisphosphate (phytate), principale composante de P organique (Po) du sol, représente une potentielle source de P disponible du sol, bio-disponible pour la plante, en lien à des activités phytases microbiennes, minéralisatrices du phytate. Afin de rechercher des rhizobiums, symbiontes de Vicia faba, efficaces dans l’utilisation du P (EUP) pour la FSN, nous avons réalisé un diagnostic nodulaire multilocalisé, en agro-écosystèmes sud de France. Le niveau d’efficacité d’utilisation de la symbiose rhizobienne (EUSR), en intra- et inter-placettes agricoles et en conditions hydroaéroponiques en serre, a été déterminé en corrélation des biomasses aériennes et nodulaires de plants de V. faba, à floraison. Parmi 59 isolats de V. faba, 26 sont aptes à minéraliser le phytate (Phy +), en milieu solide et six d'entre eux confirment une activité phytase, en culture liquide. L’intérêt d’une sélection de rhizobiums locaux aptes à une EUP pour FSN, nous a conduits à une avancée dans la sélection de marqueurs moléculaires phytases pour le criblage d’isolats rhizobiens Phy+. Mots ClésRhizobium, diversité, phytase, féverole, Vicia faba, nodulation, France-sud, agro-écosystèmeThe ability of rhizobium-legume symbiosis to fix atmospheric nitrogen can provide important services to agro-ecosystems. However, associated with biotic constraints (i) missing and/or (ii) phosphorus (P) deficiency, can limit symbiotic nitrogen fixation (SNF). Myo-inositol hexakisphosphate (phytate), the main soil organic P (Po) component, represents a potential source of soil P available for plant P bio-availability, connected with microbial phytate-mineralizing activities. In order to look for rhizobium-Vicia faba, in P use efficiency (PUE) for SNF ability, nodular diagnosis was performed from a multi-location survey in an agro-ecosystem in South France. The efficiency in use of rhizobial symbiosis (EURS) was deduced from V. faba nodule and shoot dry weight values at flowering state, and compared in intra- and inter agricultural fields and in greenhouse hydroaeroponic conditions. Among 59 V. faba isolates, 26 were able to mineralize phytate (Phy+) in solid medium and six of them confirmed phytase activity in liquid culture. Looking for local rhizobiums with PUE for SNF ability, led us to a forward step in molecular marker selection for Phy+ rhizobium isolate screening. KeywordsRhizobium, diversity, phytase, faba-bean, Vicia faba, nodulation, South-France, agro-ecosystem
45
Westhoek, Annet. "Resource allocation in the legume-rhizobia symbiosis : an integration of modelling and experimental approaches." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:66ed2e7d-85d3-4090-a822-28609ea866c7.
Abstract:
The symbiosis between plants of the legume family and nitrogen-fixing rhizobia underpins global food security. Legume crops are a major source of protein in human diets, either directly or indirectly as feed for livestock. Application of inoculant rhizobial strains is common practice in many areas, as plant growth is often nitrogen limited and the symbiosis can significantly enhance yields. However, rhizobial strains and outcomes of the symbiosis vary widely. This variation has also been studied by evolutionary biologists interested in the stability of mutualisms. They proposed that plants may prevent establishing symbioses with ineffective strains (partner choice), or provide them with fewer resources (sanctioning). I studied both mechanisms, combining modelling and experimental approaches. Mathematical modelling was used to predict how plants should allocate resources to maximise growth rates, depending on rhizobial nitrogen provision and carbon requirements and on soil nitrogen conditions. The use of marked mutant strains â easily distinguishable and differing in a single rhizobial characteristic â overcame previous experimental difficulties. It was found that pea (Pisum sativum L.) plants are not able to exert partner choice, but do sanction in a more complex way than was previously established. In line with model predictions, resources were preferentially allocated to the single â best available â strain, so that resources allocated to an intermediate-fixing strain depended on whether or not a strain providing more nitrogen was available. Contrary to model predictions, there was no indication of discrimination based on rhizobial carbon requirements. The results cannot be explained by resource allocation in proportion to nitrogen received, and indicate systemic integration of information from different nodules. I formulate a hypothesis about the underlying plant regulatory mechanisms, and discuss implications of the results for selecting inoculant strains and enhancing yields in the field. Future work will rely on further integration of theoretical and applied methods and perspectives.
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Pillai, Suresh Divakaran. "Ecology and genetic stability of Tn5 mutants of bean rhizobia in Sonoran desert soils." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184823.
Abstract:
Five transposon Tn5 mutants of bean rhizobia (Rhizobium leguminosarum b.v. phaseoli) and the wild type strain were used in ecological studies to evaluate the efficacy of transposon Tn5 as a phenotypic marker in rhizobia for ecological studies in two Sonoran desert soils. All mutants possessed chromosomal insertions of the transposable element. Survival of each mutant strain was compared to that of the wild type strain under non stress, moisture stress and temperature stress conditions in Pima silty clay loam and Brazil to sandy loam. The genetic stability of Tn5 in terms of transposition of the element within the chromosome and the Tn5 coded antibiotic resistant phenotype was determined in cells recovered throughout the survival period. Under non stress conditions, the viable Tn5 mutant population decreased in size. Two mutants showed significantly (p < 0.01) lower populations than the wild type at the end of 30 days in the silty clay loam. In the sandy loam, four of the five mutant populations were significantly lower than the wild type. Tn5 was genetically stable in both soils. Under moisture stress conditions, the decline of the Tn5 mutant and wild type populations corresponded to a decline in soil moisture content. The finer textured soil afforded more protection to the cells than the coarse textured soil. There were no indications of Tn5 instability under moisture stress. In both soils under temperature stress, sizes of all populations declined rapidly and after 12 days, the mutant cells when screened using the Tn5 coded markers were significantly less in numbers than the wild type indicating a loss of Tn5 coded antibiotic resistance phenotype. There were no significant differences in numbers between wild type and mutant cells when screened using only the intrinsic markers. DNA:DNA hybridizations confirmed that the lack of Tn5 coded antibiotic resistance phenotype was probably not due to a deletion or transposition of the element. Under non stress conditions Tn5 is a useful ecological marker, but each Tn5 mutant has to be evaluated independently under specific environmental conditions to determine the efficacy of Tn5 as an ecological marker.
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Miller, Lance Delano. "Characterization of the Chemotaxis System of the Endosymbiotic Bacterium Rhizobium leguminosarum." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19707.
Abstract:
Chemotaxis is the process by which motile bacteria navigate chemical gradients in order to position themselves in optimum environments for growth and metabolism. Sensory input from both the external environment and the internal cellular environment are sensed by chemotaxis transducers and transduced to a two-component system whose output interacts with the flagellum thereby regulating motility.
Chemotaxis has been implicated in establishing the endosymbiotic relationship between the motile alpha-proteobacterium Rhizobium leguminosarum biovar viciae and its host Pisum sativa, the pea plant. An approach combing bioinformatical sequence analysis, molecular genetics, and behavioral analysis was used to characterize the chemotaxis system of R. leguminosarum and determine its contribution to this bacterium s lifestyle.
A genome search revealed the presence of two chemotaxis gene clusters, che1 and che2. Homologs of each che cluster are major chemotaxis operons controlling flagellar motility in other bacterial species. For this reason we sought to determine the contribution of each che cluster to chemotaxis in R. leguminosarum. We found that while both che clusters contribute to the regulation of motility, che1 is the major che cluster controlling chemotaxis. Using competitive nodulation assays we determined that che1, but not che2, is essential for competitive nodulation.
The major che cluster, che1, encodes a chemotaxis transducer, IcpA-Rl, with a globin coupled sensor domain. Chemotaxis transducers with a globin coupled sensor domain comprise a large class of proteins found in bacteria and archaea. These proteins have been shown to bind heme and sense oxygen and are therefore termed HemATs for heme-binding aerotaxis transducers. However, sequence analysis of IcpA-Rl reveals that it lacks the requisite amino acid residues for heme-binding and is therefore unlikely to sense oxygen. We present evidence that IcpA-Rl is likely an energy transducer and represents a novel function of the globin coupled sensor domain in sensing energy related parameters.
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Bashore, Sarah L. aity. "Characterization of a Spontaneous Phaseolus Vulgaris Mutant with the Ability to Selectively Restrict Nodulation." Ohio University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1155747948.
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Forquer, Isaac P. "Characterization of Photosynthetic Reaction Centers from Bradyrhizobium strain BTAi 1." Wright State University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=wright1133541454.
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Maynaud, Géraldine. "Adaptation aux métaux lourds de populations de rhizobia impliquées dans la phytostabilisation de déblais miniers : Identification des mécanismes d’adaptation au Zn et au Cd, et structuration des populations de rhizobia adaptées aux sites miniers." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20074/document.
Abstract:
La symbiose entre Anthyllis vulneraria et Mesorhizobium metallidurans, mise en évidence dans l'ancienne mine Zn/Pb des Avinières à St Laurent-le-Minier (Gard) permet une entrée d'azote dans les sols grâce à la fixation biologique qui favorise l'installation d'une végétation pérenne d'intérêt pour limiter la pollution métallique via l'érosion éolienne et hydrique. M. metallidurans ayant la particularité de résister à de fortes concentrations en Zn et Cd, la recherche des gènes d'adaptation aux métaux lourds a été mise en œuvre pour mieux connaitre cette bactérie impliquée dans des opérations de phytostabilisation, par des approches de génétique moléculaire et de transcriptomie (RNAseq). Les gènes codant pour des systèmes de séquestration, d'exclusion, de réduction et d'efflux des métaux lourds, dont cadA1, codant pour une PIB-ATPase exportant Cd/Zn ont été identifiés chez deux souches métallicoles associées à Anthyllis ; M. metallidurans STM 2683T (mine des Avinières) et Mesorhizobium sp. STM 4661 (mine d'Eylie). Une étude fonctionnelle de cadA1 a permis de caractériser son rôle dans la résistance aux métaux lourds chez M. metallidurans. Ce gène a ensuite été testé comme marqueur de résistance pour étudier la diversité et la répartition des symbiotes d'Anthyllis sur des sites miniers et non pollués. Pour cela ce travail a été complété par des analyses phénotypiques de tolérance au Zn et Cd et des analyses phylogénétiques basées sur des marqueurs taxonomiques et symbiotiques. La contrainte métallique exercée par les environnements miniers semble influencer la composition et la diversité bactérienne avec une plus forte proportion (i) de phénotype métallicole lié à la présence du gène cadA1 et (ii) de rhizobia appartenant à M. metallidurans ou à une espèce très proche. La plante hôte semble quant à elle influencer la diversité symbiotique des rhizobia, indépendamment de la contrainte métalliqueEfficient nitrogen-fixing symbiosis between Anthyllis vulneraria and Mesorhizobium metallidurans, identified in the highly Zn/Pb polluted mining site of Avinières (St Laurent-le-Minier, Gard county, France) has recently been described as a potential key bioremediation agent for stimulating the growth of a sustainable plant cover and thus limit heavy metal dispersion from contaminated sites. M. metallidurans strains were shown to be resistant to high Zn and Cd concentrations. The aim of our work was to identify and characterize genes involved in heavy metal adaptation in M. metallidurans by using genetic and transcriptomic approaches (RNAseq technology). Putative genes involved in heavy metal adaptation mechanisms such as exclusion, binding, reduction and efflux, like cadA1, encoding an efflux system PIB-type ATPase involved in Zn and Cd export, were identified in two Mesorhizobium strains associated with Anthyllis: M. metallidurans STM 2683T (Avinières mine) and Mesorhizobium sp. STM 4661 (Eylie mine). Functional studies allowed us to characterize the cadA1 efflux protein as involved in metal tolerance in M. metallidurans. Then, cadA1 was used as a metal-resistance marker to study the diversity and the distribution of Anthyllis symbionts from mine soils and unpolluted soils. This work was completed by Zn- and Cd-tolerance phenotype assays and phylogenetic analyses using taxonomical and symbiotic markers. Metals in mine environments seemed to influence the bacterial composition and the diversity with a high proportion of (i) metal-tolerant phenotypes consistent with the detection of the cadA1 gene and (ii) strains belonging to the M. metallidurans species or to a bacterial species close to it. The plant-hosts seemed to impact symbiotic diversity independently of the metal-tolerant property