Bibliographies thématiques / Symbiotic diazotrophs

Littérature scientifique sur le sujet « Symbiotic diazotrophs »

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Publié le 18 mai 2024

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Articles de revues sur le sujet "Symbiotic diazotrophs"

Lema, Kimberley A., Bette L. Willis et David G. Bourne. « Corals Form Characteristic Associations with Symbiotic Nitrogen-Fixing Bacteria ». Applied and Environmental Microbiology 78, n^o 9 (17 février 2012) : 3136–44. http://dx.doi.org/10.1128/aem.07800-11.

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ABSTRACTThe complex symbiotic relationship between corals and their dinoflagellate partnerSymbiodiniumis believed to be sustained through close associations with mutualistic bacterial communities, though little is known about coral associations with bacterial groups able to fix nitrogen (diazotrophs). In this study, we investigated the diversity of diazotrophic bacterial communities associated with three common coral species (Acropora millepora,Acropora muricata, andPocillopora damicormis) from three midshelf locations of the Great Barrier Reef (GBR) by profiling the conserved subunit of thenifHgene, which encodes the dinitrogenase iron protein. Comparisons of diazotrophic community diversity among coral tissue and mucus microenvironments and the surrounding seawater revealed that corals harbor diversenifHphylotypes that differ between tissue and mucus microhabitats. Coral mucusnifHsequences displayed high heterogeneity, and many bacterial groups overlapped with those found in seawater. Moreover, coral mucus diazotrophs were specific neither to coral species nor to reef location, reflecting the ephemeral nature of coral mucus. In contrast, the dominant diazotrophic bacteria in tissue samples differed among coral species, with differences remaining consistent at all three reefs, indicating that coral-diazotroph associations are species specific. Notably, dominant diazotrophs for all coral species were closely related to the bacterial group rhizobia, which represented 71% of the total sequences retrieved from tissue samples. The species specificity of coral-diazotroph associations further supports the coral holobiont model that bacterial groups associated with corals are conserved. Our results suggest that, as in terrestrial plants, rhizobia have developed a mutualistic relationship with corals and may contribute fixed nitrogen toSymbiodinium.

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Rädecker, Nils, Claudia Pogoreutz, Hagen M. Gegner, Anny Cárdenas, Gabriela Perna, Laura Geißler, Florian Roth et al. « Heat stress reduces the contribution of diazotrophs to coral holobiont nitrogen cycling ». ISME Journal 16, n^o 4 (2 décembre 2021) : 1110–18. http://dx.doi.org/10.1038/s41396-021-01158-8.

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AbstractEfficient nutrient cycling in the coral-algal symbiosis requires constant but limited nitrogen availability. Coral-associated diazotrophs, i.e., prokaryotes capable of fixing dinitrogen, may thus support productivity in a stable coral-algal symbiosis but could contribute to its breakdown when overstimulated. However, the effects of environmental conditions on diazotroph communities and their interaction with other members of the coral holobiont remain poorly understood. Here we assessed the effects of heat stress on diazotroph diversity and their contribution to holobiont nutrient cycling in the reef-building coral Stylophora pistillata from the central Red Sea. In a stable symbiotic state, we found that nitrogen fixation by coral-associated diazotrophs constitutes a source of nitrogen to the algal symbionts. Heat stress caused an increase in nitrogen fixation concomitant with a change in diazotroph communities. Yet, this additional fixed nitrogen was not assimilated by the coral tissue or the algal symbionts. We conclude that although diazotrophs may support coral holobiont functioning under low nitrogen availability, altered nutrient cycling during heat stress abates the dependence of the coral host and its algal symbionts on diazotroph-derived nitrogen. Consequently, the role of nitrogen fixation in the coral holobiont is strongly dependent on its nutritional status and varies dynamically with environmental conditions.

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SUN, WENLI, MOHAMAD HESAM SHAHRAJABIAN et QI CHENG. « Nitrogen Fixation and Diazotrophs – A Review ». Romanian Biotechnological Letters 26, n^o 4 (29 juin 2021) : 2834–45. http://dx.doi.org/10.25083/rbl/26.4/2834-2845.

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Nitrogen fixation involves formation of ammonium from N2, which needs a high input of energy. Biological nitrogen fixation utilizes the enzyme nitrogenase and ATP to fix nitrogen. Nitrogenase contains a Fe-protein and a Mo-Fe-protein and other metal cofactors. Soil diazotrophs possess the function of fixing atmospheric N2 into biologically available ammonium in ecosystems. In Aechaea, nitrogen fixation has been reported in some methanogens such as Methanobacteriales, Methanococcales, and Methanosarcinales. Community structure and diversity of diazotrophic are correlated with soil pH. All known organisms which involve in nitrogen-fixing which are called diazatrophs are prokaryotes, and both bacterial and archaeal domains are responsible for that. Diazotrophs are categorized into two main groups namely: root-nodule bacteria and plant growth-promoting rhizobacteria. Diazotrophs include free living bacteria, such as Azospirillum, Cupriavidus, and some sulfate reducing bacteria, and symbiotic diazotrophs such Rhizobium and Frankia. Two important parameters which may affect diazotroph communities are temperature and soil moisture in different seasons. To have sustainable agriculture, replacing expensive chemical nitrogen fertilizers with environmentally friendly ways is the most accepted practice.

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Wu, Mandi, Shengzhican Li, Jie Bai, Kezhen Wang, Yang Qu, Mingxiu Long, Peizhi Yang, Tianming Hu et Shubin He. « Arbuscular Mycorrhizal Fungi and Diazotrophic Diversity and Community Composition Responses to Soybean Genotypes from Different Maturity Groups ». Agronomy 13, n^o 7 (26 juin 2023) : 1713. http://dx.doi.org/10.3390/agronomy13071713.

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Soybeans can simultaneously form tripartite symbiotic associations with arbuscular mycorrhizal fungi (AMF) and diazotrophs. However, no studies have explored whether soybean genotypes differing in their maturity groups (MGs) may have implications for the recruitment of rhizosphere soil AMF and diazotrophs. We investigated the diversity and community compositions of AMF and diazotrophs in three soybean genotypes differing in their maturity groups (MG) using high-throughput sequencing. The soybean MGs were MG1.4, MG2.2, and MG3.8, representing early, standard, and late maturity, respectively, for the study region. Soil chemical properties and yield-related traits were determined, and co-occurrence network patterns and drivers were also analyzed. The results obtained demonstrated that AMF richness and diversity were relatively stable in the three soybean genotypes, but noticeable differences were observed in diazotrophs, with late maturity being significantly higher than early maturity. However, there were differences in AMF and diazotrophic composition among different MG genotypes, and the changes in the proportion of dominant species in the community were necessarily related to MG genotypes. Co-occurrence network analysis showed that the positive correlation between AMF and diazotrophs gradually decreased in earlier MG genotypes than in the other later MG genotypes. The results of the structural equation model analysis showed that soil organic carbon, AMF, diversity of soil nutrients, and extracellular enzyme activities were important factors driving soybean yield change, with organic carbon accounting for more than 80% of the pathways analyzed. These results suggest that soybean genotype selection based on MG plays an important role in recruiting both AMF and diazotrophic communities, and in comparison to AMF, diazotrophs are more responsive to the different MG genotypes.

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Stenegren, Marcus, Andrea Caputo, Carlo Berg, Sophie Bonnet et Rachel A. Foster. « Distribution and drivers of symbiotic and free-living diazotrophic cyanobacteria in the western tropical South Pacific ». Biogeosciences 15, n^o 5 (15 mars 2018) : 1559–78. http://dx.doi.org/10.5194/bg-15-1559-2018.

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Abstract. The abundance and distribution of cyanobacterial diazotrophs were quantified in two regions (Melanesian archipelago, MA; and subtropical gyre, SG) of the western tropical South Pacific using nifH quantitative polymerase chain reaction (qPCR) assays. UCYN-A1 and A2 host populations were quantified using 18S rRNA qPCR assays including one newly developed assay. All phylotypes were detected in the upper photic zone (0–50 m), with higher abundances in the MA region. Trichodesmium and UCYN-B dominated and ranged from 2.18 × 102 to 9.41 × 106 and 1.10 × 102 to 2.78 × 106 nifH copies L−1, respectively. Het-1 (symbiont of Rhizosolenia diatoms) was the next most abundant (1.40 × 101–1.74 × 105 nifH copies L−1) and co-occurred with het-2 and het-3. UCYN-A1 and A2 were the least abundant diazotrophs and were below detection (bd) in 63 and 79, respectively, of 120 samples. In addition, in up to 39 % of samples in which UCYN-A1 and A2 were detected, their respective hosts were bd. Pairwise comparisons of the nifH abundances and various environmental parameters supported two groups: a deep-dwelling group (45 m) comprised of UCYN-A1 and A2 and a surface group (0–15 m) comprised of Trichodesmium, het-1 and het-2. Temperature and photosynthetically active radiation were positively correlated with the surface group, while UCYN-A1 and A2 were positively correlated with depth, salinity, and oxygen. Similarly, in a meta-analysis of 11 external datasets, all diazotrophs, except UCYN-A were correlated with temperature. Combined, our results indicate that conditions favoring the UCYN-A symbiosis differ from those of diatom diazotroph associations and free-living cyanobacterial diazotrophs.

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Thi Hieu Thu, Nguyen, Trinh Cao Son, Dang Thu Trang, Nguyen Thi My Le, Nguyen Duy Toi, Nguyen Thi Van et Dinh Thuy Hang. « Indigenous diazotrophs and their effective properties for organic agriculture ». Vietnam Journal of Biotechnology 20, n^o 4 (28 décembre 2022) : 751–60. http://dx.doi.org/10.15625/1811-4989/17070.

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Nitrogen-fixing microorganisms (diazotrophs) converting the atmospheric N2 into usable form NH4 are considered the key players in the nitrogen cycle, chiefly responsible for the enriching nitrogen content in the soils. Globally, biological fixation of N2 greatly contributes to plant growth, lessens the need for chemical fertilizers, and thus contributes to the mitigation of greenhouse gases NOx. In this study, diazotrophic bacterial strains were isolated from rhizosphere soils and root nodules of legume and non-legume plants in Vietnam. Quantitative analyzes by the acetylene reduction assay showed that the isolates have high nitrogen fixation activity compared with that of reference strain Azospirillum vinelandii KCTC 2426. In addition, other effective capabilities of the isolated strains toward supporting agriculture were investigated, i.e. synthesizing IAA and siderophore for promoting plant growth, or producing exopolysaccharides for maintaining soil moisture. Taxonomic positions of the isolated strains were identified based on the comparative analyses of sequences of the 16S rDNA and gene related to nitrogen fixation (nifH), revealing a high taxonomic diversity among free-living and symbiotic diazotrophic isolates. Direct support of the selected isolates to plant growth was proven in experiments with mung beans under laboratory conditions. Thus, the native diazotrophic strains obtained in this study would be good microbial sources for application in organic agriculture and soil amendment.

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Inomura, Keisuke, Christopher L. Follett, Takako Masuda, Meri Eichner, Ondřej Prášil et Curtis Deutsch. « Carbon Transfer from the Host Diatom Enables Fast Growth and High Rate of N2 Fixation by Symbiotic Heterocystous Cyanobacteria ». Plants 9, n^o 2 (4 février 2020) : 192. http://dx.doi.org/10.3390/plants9020192.

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Diatom–diazotroph associations (DDAs) are symbioses where trichome-forming cyanobacteria support the host diatom with fixed nitrogen through dinitrogen (N2) fixation. It is inferred that the growth of the trichomes is also supported by the host, but the support mechanism has not been fully quantified. Here, we develop a coarse-grained, cellular model of the symbiosis between Hemiaulus and Richelia (one of the major DDAs), which shows that carbon (C) transfer from the diatom enables a faster growth and N2 fixation rate by the trichomes. The model predicts that the rate of N2 fixation is 5.5 times that of the hypothetical case without nitrogen (N) transfer to the host diatom. The model estimates that 25% of fixed C from the host diatom is transferred to the symbiotic trichomes to support the high rate of N2 fixation. In turn, 82% of N fixed by the trichomes ends up in the host. Modeled C fixation from the vegetative cells in the trichomes supports only one-third of their total C needs. Even if we ignore the C cost for N2 fixation and for N transfer to the host, the total C cost of the trichomes is higher than the C supply by their own photosynthesis. Having more trichomes in a single host diatom decreases the demand for N2 fixation per trichome and thus decreases their cost of C. However, even with five trichomes, which is about the highest observed for Hemiaulus and Richelia symbiosis, the model still predicts a significant C transfer from the diatom host. These results help quantitatively explain the observed high rates of growth and N2 fixation in symbiotic trichomes relative to other aquatic diazotrophs.

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Mutalipassi, Mirko, Gennaro Riccio, Valerio Mazzella, Christian Galasso, Emanuele Somma, Antonia Chiarore, Donatella de Pascale et Valerio Zupo. « Symbioses of Cyanobacteria in Marine Environments : Ecological Insights and Biotechnological Perspectives ». Marine Drugs 19, n^o 4 (16 avril 2021) : 227. http://dx.doi.org/10.3390/md19040227.

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Cyanobacteria are a diversified phylum of nitrogen-fixing, photo-oxygenic bacteria able to colonize a wide array of environments. In addition to their fundamental role as diazotrophs, they produce a plethora of bioactive molecules, often as secondary metabolites, exhibiting various biological and ecological functions to be further investigated. Among all the identified species, cyanobacteria are capable to embrace symbiotic relationships in marine environments with organisms such as protozoans, macroalgae, seagrasses, and sponges, up to ascidians and other invertebrates. These symbioses have been demonstrated to dramatically change the cyanobacteria physiology, inducing the production of usually unexpressed bioactive molecules. Indeed, metabolic changes in cyanobacteria engaged in a symbiotic relationship are triggered by an exchange of infochemicals and activate silenced pathways. Drug discovery studies demonstrated that those molecules have interesting biotechnological perspectives. In this review, we explore the cyanobacterial symbioses in marine environments, considering them not only as diazotrophs but taking into consideration exchanges of infochemicals as well and emphasizing both the chemical ecology of relationship and the candidate biotechnological value for pharmaceutical and nutraceutical applications.

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S. F., Kozar. « DIAZOTROPH ACTIVITY REGULATING STRATEGY UNDER THEIR INTRODUCTION IN AGROCENOSES ». Agriciltural microbiology 33 (18 juin 2021) : 33–43. http://dx.doi.org/10.35868/1997-3004.33.33-43.

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Objective. Investigate approaches to managing the activity of soil diazotrophs and propose a strategy for its regulation. Methods. Theoretical, vegetation and field experiments, microbiological, gas chromatographic, mathematical and statistical. Results. The activity of beneficial soil microorganisms can change under the action of temperature, humidity, chemical compounds of various origin, and other microorganisms. It was established that, taking into account a significant variety of factors, it is necessary to develop a set of specific ways to increase the growth and functional activity of nitrogen-fixing bacteria, as well as their viability. It has been proved that the combination of diazotrophs forms an effective symbiotic leguminous-rhizobial system, which provides additional biological nitrogen in agrocenoses. At the same time, there was an increase in plant mass, chlorophyll content in the leaves, protein and oil content in the products. The combined use of diazotrophs increases the yield, in particular, soybeans by 9–16 % compared with inoculation by pure bacterial culture. Conclusion. Based on the analysis and generalization of the obtained research results, a strategy for regulating the activity of diazotrophs for their effective introduction into agrocenoses is proposed, which consists in combining bacteria of different species, selecting conditions for their co-cultivation and application upon stabilisation of the number of viable bacterial cells. The proposed strategy involves solving the problem by obtaining an inoculant, which is characterized by a high titre and a stable number of viable cells, which allows to obtain an effective nitrogen-fixing system. The strategy is tried-and-tested on the example of regulating the growth and functional activity of soybean nodule bacteria by combining diazotrophs of different species, substantiating the conditions of their co-cultivation and application to ensure positive interaction in the form of commensalism, as well as by regulating viability of diazotrophs by adding stabilisers to the medium.

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Maeda, Isamu. « Potential of Phototrophic Purple Nonsulfur Bacteria to Fix Nitrogen in Rice Fields ». Microorganisms 10, n^o 1 (24 décembre 2021) : 28. http://dx.doi.org/10.3390/microorganisms10010028.

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Biological nitrogen fixation catalyzed by Mo-nitrogenase of symbiotic diazotrophs has attracted interest because its potential to supply plant-available nitrogen offers an alternative way of using chemical fertilizers for sustainable agriculture. Phototrophic purple nonsulfur bacteria (PNSB) diazotrophically grow under light anaerobic conditions and can be isolated from photic and microaerobic zones of rice fields. Therefore, PNSB as asymbiotic diazotrophs contribute to nitrogen fixation in rice fields. An attempt to measure nitrogen in the oxidized surface layer of paddy soil estimates that approximately 6–8 kg N/ha/year might be accumulated by phototrophic microorganisms. Species of PNSB possess one of or both alternative nitrogenases, V-nitrogenase and Fe-nitrogenase, which are found in asymbiotic diazotrophs, in addition to Mo-nitrogenase. The regulatory networks control nitrogenase activity in response to ammonium, molecular oxygen, and light irradiation. Laboratory and field studies have revealed effectiveness of PNSB inoculation to rice cultures on increases of nitrogen gain, plant growth, and/or grain yield. In this review, properties of the nitrogenase isozymes and regulation of nitrogenase activities in PNSB are described, and research challenges and potential of PNSB inoculation to rice cultures are discussed from a viewpoint of their applications as nitrogen biofertilizer.

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Thèses sur le sujet "Symbiotic diazotrophs"

Thakur, Subarna. « In-silico characterization of some nitrogenase proteins from symbiotic diazotrophs and cyanobacteria ». Thesis, University of North Bengal, 2013. http://ir.nbu.ac.in/handle/123456789/953.

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Horak, Rachel Elizabeth Ann. « Controls on nitrogen fixation and nitrogen release in a diazotrophic endosymbiont of shipworms ». Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37238.

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Nitrogen fixation is an ecologically important microbial process that can contribute bioavailable combined N to habitats low in N. Shipworms, or wood-boring bivalves, host N2-fixing and cellulolytic symbiotic bacteria in gill bacteriocytes, which have been implicated as a necessary adaptation to an N-poor C-rich (wooden) diet. Shipworm symbionts are known to fix N within the gill habitat and newly fixed N is subsequently incorporated into non-symbiont containing host tissue. The presence of N2-fixation in gill bacteriocytes presents a conundrum because N2-fixation is tightly regulated by oxygen in most other diazotrophic microbes. Also, the direct evidence of new N being incorporated into the host tissue indicates that there are potentially complex nutrient cycles in this symbiosis, which have not been investigated. We used the cultivated symbiont Teredinibacter turnerae, which has been isolated from many shipworm species, as a model organism to elucidate controls on N2-fixation and N release in the shipworm symbiosis. Our results indicate that headspace oxygen concentration does not control biomass specific N2-fixation and respiration activity in T. turnerae, but it does influence the magnitude of the growth rate and timing of culture growth. Also, we examined the controls of oxygen on inorganic nutrient uptake rates, and documented a small amount of dissolved inorganic nitrogen release. While the N budget is only partially balanced, we provide indirect evidence for the allocation of fixed N to the excretion of exopolymeric substances and dissolved organic nitrogen; future studies that measure these additional N sinks are necessary to close the N budget. Although there are limitations of using pure cultures to investigate a complex symbiotic system, this study provides direct experimental evidence that T. turnerae has adaptations that are conducive to N2-fixation in gill bacteriocytes.

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Chapitres de livres sur le sujet "Symbiotic diazotrophs"

Thakur, Subarna, Asim K. Bothra et Arnab Sen. « Exploring the Genomes of Symbiotic Diazotrophs with Relevance to Biological Nitrogen Fixation ». Dans Agricultural Bioinformatics, 235–57. New Delhi : Springer India, 2014. http://dx.doi.org/10.1007/978-81-322-1880-7_14.

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Triplett, Eric W. « Diazotrophic endophytes : progress and prospects for nitrogen fixation in monocots ». Dans Current Issues in Symbiotic Nitrogen Fixation, 29–38. Dordrecht : Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-011-5700-1_4.

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Palus, James A., James Borneman, Paul W. Ludden et Eric W. Triplett. « A diazotrophic bacterial endophyte isolated from stems of Zea mays L. and Zea luxurians Iltis and Doebley ». Dans Current Issues in Symbiotic Nitrogen Fixation, 135–42. Dordrecht : Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-011-5700-1_19.

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Das, Arundhati, Rajkamal Srivastava, Vishal Patil et Sudipta Tripathi. « Studies on the Non-symbiotic Diazotrophic Bacterial Population and Efficiency of Nitrogen Fixation in Coastal Saline Soils from Sagar Island, West Bengal ». Dans Water Science and Technology Library, 299–305. Singapore : Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-5795-3_25.

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