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Lema, Kimberley A., Bette L. Willis, and David G. Bourne. "Corals Form Characteristic Associations with Symbiotic Nitrogen-Fixing Bacteria." Applied and Environmental Microbiology 78, no. 9 (February 17, 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, no. 4 (December 2, 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, and QI CHENG. "Nitrogen Fixation and Diazotrophs – A Review." Romanian Biotechnological Letters 26, no. 4 (June 29, 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, and Shubin He. "Arbuscular Mycorrhizal Fungi and Diazotrophic Diversity and Community Composition Responses to Soybean Genotypes from Different Maturity Groups." Agronomy 13, no. 7 (June 26, 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, and Rachel A. Foster. "Distribution and drivers of symbiotic and free-living diazotrophic cyanobacteria in the western tropical South Pacific." Biogeosciences 15, no. 5 (March 15, 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, and Dinh Thuy Hang. "Indigenous diazotrophs and their effective properties for organic agriculture." Vietnam Journal of Biotechnology 20, no. 4 (December 28, 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, and Curtis Deutsch. "Carbon Transfer from the Host Diatom Enables Fast Growth and High Rate of N2 Fixation by Symbiotic Heterocystous Cyanobacteria." Plants 9, no. 2 (February 4, 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, and Valerio Zupo. "Symbioses of Cyanobacteria in Marine Environments: Ecological Insights and Biotechnological Perspectives." Marine Drugs 19, no. 4 (April 16, 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 (June 18, 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, no. 1 (December 24, 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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SUN, Wenli, Mohamad H. SHAHRAJABIAN, and Qi CHENG. "Archaea, bacteria and termite, nitrogen fixation and sustainable plants production." Notulae Botanicae Horti Agrobotanici Cluj-Napoca 49, no. 2 (May 5, 2021): 12172. http://dx.doi.org/10.15835/nbha49212172.
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Certain bacteria and archaea are responsible for biological nitrogen fixation. Metabolic pathways usually are common between archaea and bacteria. 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. Three types of nitrogenase are iron and molybdenum (Fe/Mo), iron and vanadium (Fe/V) or iron only (Fe). The Mo-nitrogenase have a higher specific activity which is expressed better when Molybdenum is available. The best hosts for Rhizobium legumiosarum are Pisum, Vicia, Lathyrus and Lens; Trifolium for Rhizobium trifolii; Phaseolus vulgaris, Prunus angustifolia for Rhizobium phaseoli; Medicago, Melilotus and Trigonella for Rhizobium meliloti; Lupinus and Ornithopus for Lupini, and Glycine max for Rhizobium japonicum. Termites have significant key role in soil ecology, transporting and mixing soil. Termite gut microbes supply the enzymes required to degrade plant polymers, synthesize amino acids, recycle nitrogenous waste and fix atmospheric nitrogen. The positive effects of Arbuscular mycorrhizal (AM) fungi such as growth promotion, increased root length, leaf area, stem diameter, transplant performance and tolerance to stresses have been reported previously.
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De Meyer, Sofie E., Leah Briscoe, Pilar Martínez-Hidalgo, Christina M. Agapakis, Paulina Estrada de-los Santos, Rekha Seshadri, Wayne Reeve, et al. "Symbiotic Burkholderia Species Show Diverse Arrangements of nif/fix and nod Genes and Lack Typical High-Affinity Cytochrome cbb3 Oxidase Genes." Molecular Plant-Microbe Interactions® 29, no. 8 (August 2016): 609–19. http://dx.doi.org/10.1094/mpmi-05-16-0091-r.
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Genome analysis of fourteen mimosoid and four papilionoid beta-rhizobia together with fourteen reference alpha-rhizobia for both nodulation (nod) and nitrogen-fixing (nif/fix) genes has shown phylogenetic congruence between 16S rRNA/MLSA (combined 16S rRNA gene sequencing and multilocus sequence analysis) and nif/fix genes, indicating a free-living diazotrophic ancestry of the beta-rhizobia. However, deeper genomic analysis revealed a complex symbiosis acquisition history in the beta-rhizobia that clearly separates the mimosoid and papilionoid nodulating groups. Mimosoid-nodulating beta-rhizobia have nod genes tightly clustered in the nodBCIJHASU operon, whereas papilionoid-nodulating Burkholderia have nodUSDABC and nodIJ genes, although their arrangement is not canonical because the nod genes are subdivided by the insertion of nif and other genes. Furthermore, the papilionoid Burkholderia spp. contain duplications of several nod and nif genes. The Burkholderia nifHDKEN and fixABC genes are very closely related to those found in free-living diazotrophs. In contrast, nifA is highly divergent between both groups, but the papilionoid species nifA is more similar to alpha-rhizobia nifA than to other groups. Surprisingly, for all Burkholderia, the fixNOQP and fixGHIS genes required for cbb3 cytochrome oxidase production and assembly are missing. In contrast, symbiotic Cupriavidus strains have fixNOQPGHIS genes, revealing a divergence in the evolution of two distinct electron transport chains required for nitrogen fixation within the beta-rhizobia.
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Pyle, Amy E., Allison M. Johnson, and Tracy A. Villareal. "Isolation, growth, and nitrogen fixation rates of the Hemiaulus-Richelia (diatom-cyanobacterium) symbiosis in culture." PeerJ 8 (October 8, 2020): e10115. http://dx.doi.org/10.7717/peerj.10115.
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Nitrogen fixers (diazotrophs) are often an important nitrogen source to phytoplankton nutrient budgets in N-limited marine environments. Diazotrophic symbioses between cyanobacteria and diatoms can dominate nitrogen-fixation regionally, particularly in major river plumes and in open ocean mesoscale blooms. This study reports the successful isolation and growth in monocultures of multiple strains of a diatom-cyanobacteria symbiosis from the Gulf of Mexico using a modified artificial seawater medium. We document the influence of light and nutrients on nitrogen fixation and growth rates of the host diatom Hemiaulus hauckii Grunow together with its diazotrophic endosymbiont Richelia intracellularis Schmidt, as well as less complete results on the Hemiaulus membranaceus-R. intracellularis symbiosis. The symbioses rates reported here are for the joint diatom-cyanobacteria unit. Symbiont diazotrophy was sufficient to support both the host diatom and cyanobacteria symbionts, and the entire symbiosis replicated and grew without added nitrogen. Maximum growth rates of multiple strains of H. hauckii symbioses in N-free medium with N2 as the sole N source were 0.74–0.93 div d−1. Growth rates followed light saturation kinetics in H. hauckii symbioses with a growth compensation light intensity (EC) of 7–16 µmol m−2s−1and saturation light level (EK) of 84–110 µmol m−2s−1. Nitrogen fixation rates by the symbiont while within the host followed a diel pattern where rates increased from near-zero in the scotophase to a maximum 4–6 h into the photophase. At the onset of the scotophase, nitrogen-fixation rates declined over several hours to near-zero values. Nitrogen fixation also exhibited light saturation kinetics. Maximum N2 fixation rates (84 fmol N2 heterocyst−1h−1) in low light adapted cultures (50 µmol m−2s−1) were approximately 40–50% of rates (144–154 fmol N2 heterocyst−1h−1) in high light (150 and 200 µmol m−2s−1) adapted cultures. Maximum laboratory N2 fixation rates were ~6 to 8-fold higher than literature-derived field rates of the H. hauckii symbiosis. In contrast to published results on the Rhizosolenia-Richelia symbiosis, the H. hauckii symbiosis did not use nitrate when added, although ammonium was consumed by the H. hauckii symbiosis. Symbiont-free host cell cultures could not be established; however, a symbiont-free H. hauckii strain was isolated directly from the field and grown on a nitrate-based medium that would not support DDA growth. Our observations together with literature reports raise the possibility that the asymbiotic H. hauckii are lines distinct from an obligately symbiotic H. hauckii line. While brief descriptions of successful culture isolation have been published, this report provides the first detailed description of the approaches, handling, and methodologies used for successful culture of this marine symbiosis. These techniques should permit a more widespread laboratory availability of these important marine symbioses.
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Che, Rongxiao, Yongcui Deng, Fang Wang, Weijin Wang, Zhihong Xu, Yanbin Hao, Kai Xue, et al. "Autotrophic and symbiotic diazotrophs dominate nitrogen-fixing communities in Tibetan grassland soils." Science of The Total Environment 639 (October 2018): 997–1006. http://dx.doi.org/10.1016/j.scitotenv.2018.05.238.
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Cvijanovic, Gorica, Nada Milosevic, and Mirjana Jarak. "The importance of diazotrophs as biofertilisers in the maize and soybean production." Genetika 39, no. 3 (2007): 395–404. http://dx.doi.org/10.2298/gensr0703395c.
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The contemporary food production requires the preservation of soil productivity with the simultaneous maintenance of the yield level accomplished with the appropriate fertilizing. The maize and soybean production is unimaginable without fertilizers and the application of information within the filed of nitrogen fixation. The application of fertilizers has been increasing. Diazotrophs are microorganisms with the ability to fix atmospheric nitrogen and to convert it in forms available to plants. Therefore, effects of different rates of mineral nitrogen (80, 120 and 160 kg N ha-1 in maize and half of the mentioned rates in soybean), as well as, maize seed bacterisation with the associative species (Azotobacter chroococcum, Azospirillum lipoferum, Klebsiella planticola, Beijerinckia derxi) and soybean with the symbiotic species (Bradyrhizobium japonicum) and their mixture on soil biogeny and yield quality and quantity were studied. The studied parameters in maize had higher values under conditions of bacterisation and fertilization with 80 kg N ha-1, while the mixture of diazotrophs and fertilization with 40 kg N ha-1 resulted in higher values of studied parameters in soybean. It is possible to produce organic/healthy food with the maintenance of soil biogeny if diazotrophs are incorporated into the soil with lower rates of mineral nitrogen. This possibility is a basic prerequisite for sustainable agriculture.
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Das, A. C., and D. Saha. "Influence of diazotrophic inoculations on nitrogen nutrition of rice." Soil Research 41, no. 8 (2003): 1543. http://dx.doi.org/10.1071/sr03115.
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An experiment was conducted in microplots (7 by 7m) to investigate the effect of 2 non-symbiotic N2-fixing bacteria [Azotobacter (strain CS1) and Azospirillum (strain CM4)] in the presence of 50 kg N/ha on the performances of the diazotrophs with respect to nitrogen accretion and its transformation in the rhizosphere soils of rice (Oryza sativa L. cv. IR-36). In most cases, a successful inoculation of the diazotrophs was recorded, with the proliferation of Azotobacter and Azospirillum, either alone or in combination, in the rhizosphere soils, and nitrogenase activity (C2H2 reduction) of the microbes was present in rice roots. The uninoculated soil receiving 100 kg N/ha recorded the highest amount of total nitrogen, non-hydrolysable organic nitrogen, available nitrogen, and hydrolysable organic nitrogen content in the rhizosphere soils, resulting in greater yield of the crop. Inoculation of the diazotrophs substantially increased different fractions of nitrogen content in the rhizosphere soils, and the increase in total nitrogen, non-hydrolysable organic nitrogen, and hydrolysable organic nitrogen was greater due to Azotobacter than either Azospirillum or a combination of Azotobacter and Azospirillum. Total and mineral nitrogen content increased at maximum tillering to flowering stages of the crop, followed by a decline at maturity, whereas, hydrolysable organic nitrogen decreased with a concomitant increase in non-hydrolysable fraction with the age of the crop.
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Gupta, V. V. S. R., S. J. Kroker, M. Hicks, C. W. Davoren, K. Descheemaeker, and R. Llewellyn. "Nitrogen cycling in summer active perennial grass systems in South Australia: non-symbiotic nitrogen fixation." Crop and Pasture Science 65, no. 10 (2014): 1044. http://dx.doi.org/10.1071/cp14109.
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Non-symbiotic nitrogen (N2) fixation by diazotrophic bacteria is a potential source for biological N inputs in non-leguminous crops and pastures. Perennial grasses generally add larger quantities of above- and belowground plant residues to soil, and so can support higher levels of soil biological activity than annual crops. In this study, the hypothesis is tested that summer-active perennial grasses can provide suitable microsites with the required carbon supply for N2 fixation by diazotrophs, in particular during summer, through their rhizosphere contribution. In a field experiment on a Calcarosol at Karoonda, South Australia, during summer 2011, we measured populations of N2-fixing bacteria by nifH-PCR quantification and the amount of 15N2 fixed in the rhizosphere and roots of summer-active perennial grasses. Diazotrophic N2 fixation estimates for the grass roots ranged between 0.92 and 2.35 mg 15N kg–1 root day–1. Potential rates of N2 fixation for the rhizosphere soils were 0.84–1.4 mg 15N kg–1 soil day–1 whereas the amount of N2 fixation in the bulk soil was 0.1–0.58 mg 15N kg–1 soil day–1. Populations of diazotrophic bacteria in the grass rhizosphere soils (2.45 × 106 nifH gene copies g–1 soil) were similar to populations in the roots (2.20 × 106 nifH gene copies g–1 roots) but the diversity of diazotrophic bacteria was significantly higher in the rhizosphere than the roots. Different grass species promoted the abundance of specific members of the nifH community, suggesting a plant-based selection from the rhizosphere microbial community. The results show that rhizosphere and root environments of summer-active perennial grasses support significant amounts of non-symbiotic N2 fixation during summer compared with cropping soils, thus contributing to biological N inputs into the soil N cycle. Some pasture species also maintained N2 fixation in October (spring), when the grasses were dormant, similar to that found in soils under a cereal crop. Surface soils in the rainfed cropping regions of southern Australia are generally low in soil organic matter and thus have lower N-supply capacity. The greater volume of rhizosphere soil under perennial grasses and carbon inputs belowground can potentially change the balance between N immobilisation and mineralisation processes in the surface soils in favour of immobilisation, which in turn contributes to reduced N losses from leaching.
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Chen, Wen-Ming, Lionel Moulin, Cyril Bontemps, Peter Vandamme, Gilles Béna, and Catherine Boivin-Masson. "Legume Symbiotic Nitrogen Fixation byβ-Proteobacteria Is Widespread inNature." Journal of Bacteriology 185, no. 24 (December 15, 2003): 7266–72. http://dx.doi.org/10.1128/jb.185.24.7266-7272.2003.
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ABSTRACT Following the initial discovery of two legume-nodulating Burkholderia strains (L. Moulin, A. Munive, B. Dreyfus, and C. Boivin-Masson, Nature 411:948-950, 2001), we identified as nitrogen-fixing legume symbionts at least 50 different strains of Burkholderia caribensis and Ralstonia taiwanensis, all belonging to the β-subclass of proteobacteria, thus extending the phylogenetic diversity of the rhizobia. R. taiwanensis was found to represent 93% of the Mimosa isolates in Taiwan, indicating thatβ -proteobacteria can be the specific symbionts of a legume. The nod genes of rhizobial β-proteobacteria (β-rhizobia) are very similar to those of rhizobia from theα -subclass (α-rhizobia), strongly supporting the hypothesis of the unique origin of common nod genes. Theβ -rhizobial nod genes are located on a 0.5-Mb plasmid, together with the nifH gene, in R. taiwanensis and Burkholderia phymatum. Phylogenetic analysis of available nodA gene sequences clustered β-rhizobial sequences in two nodA lineages intertwined with α-rhizobial sequences. On the other hand, theβ -rhizobia were grouped with free-living nitrogen-fixingβ -proteobacteria on the basis of the nifH phylogenetic tree. These findings suggest that β-rhizobia evolved from diazotrophs through multiple lateral nod gene transfers.
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Bellés-Sancho, Paula, Martina Lardi, Yilei Liu, Sebastian Hug, Marta Adriana Pinto-Carbó, Nicola Zamboni, and Gabriella Pessi. "Paraburkholderia phymatum Homocitrate Synthase NifV Plays a Key Role for Nitrogenase Activity during Symbiosis with Papilionoids and in Free-Living Growth Conditions." Cells 10, no. 4 (April 20, 2021): 952. http://dx.doi.org/10.3390/cells10040952.
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Homocitrate is an essential component of the iron-molybdenum cofactor of nitrogenase, the bacterial enzyme that catalyzes the reduction of dinitrogen (N2) to ammonia. In nitrogen-fixing and nodulating alpha-rhizobia, homocitrate is usually provided to bacteroids in root nodules by their plant host. In contrast, non-nodulating free-living diazotrophs encode the homocitrate synthase (NifV) and reduce N2 in nitrogen-limiting free-living conditions. Paraburkholderia phymatum STM815 is a beta-rhizobial strain, which can enter symbiosis with a broad range of legumes, including papilionoids and mimosoids. In contrast to most alpha-rhizobia, which lack nifV, P. phymatum harbors a copy of nifV on its symbiotic plasmid. We show here that P. phymatum nifV is essential for nitrogenase activity both in root nodules of papilionoid plants and in free-living growth conditions. Notably, nifV was dispensable in nodules of Mimosa pudica despite the fact that the gene was highly expressed during symbiosis with all tested papilionoid and mimosoid plants. A metabolome analysis of papilionoid and mimosoid root nodules infected with the P. phymatum wild-type strain revealed that among the approximately 400 measured metabolites, homocitrate and other metabolites involved in lysine biosynthesis and degradation have accumulated in all plant nodules compared to uninfected roots, suggesting an important role of these metabolites during symbiosis.
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Lohosha, O. V., Yu O. Vorobei, and N. O. Leonova. "Symbiotic Efficiency and Cytokinin Activity of New Mesorhizobium cicerі Strains." Mikrobiolohichnyi Zhurnal 85, no. 1 (February 23, 2023): 3–11. http://dx.doi.org/10.15407/microbiolj85.01.003.
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The efficiency of the introduction of nodule bacteria, microsymbionts of legumes in agrocenoses, largely depends on the activity of biologically active substances’ biosynthesis by diazotrophs. Seed bacterization with effective rhizobia strains capable of synthesizing exometabolites for phytostimulating activity not only promotes the formation and functioning of symbiosis but also creates the conditions for increasing plant resistance to adverse environmental conditions. The aim of the work was to research the symbiotic activity, efficiency and ability of chickpea rhizobia new strains to biosynthesize phytohormonal exometabolites of cytokinin nature. Methods. Microbiological, physiological, cytological, biochemical, and physicochemical. Results. New strains of Mesorhizobium ciceri ND-101 and Mesorhizobium ciceri ND-64 were shown to have different symbiotic activity. The efficiency of inoculation of Skarb chickpea seeds with bacterial suspension of Mesorhizobiu mciceri ND-101 was at the same level with the industrial strain of Mesorhizobium ciceri H-12. Bacterization of Mesorhizobium ciceri ND-64 increased the chickpea roots nodules by 69%, their weight by 74%, and nitrogenase activity by 73% relative to the positive control (inoculation with Mesorhizobium ciceri H-12), as well as increased chickpeas yield by 22%. It was established that Mesorhizobium ciceri ND-64 strain exhibits the highest cytokinin activity in the bioassay. Cytokinins in the total amount of 174.94 μg/g of completely dry biomass were detected in the culture medium of Mesorhizobium ciceri ND-64, which is 53% higher than that of Mesorhizobium ciceri ND-101 strain and 99% higher than that of Mesorhizobium ciceri H-12 strain. Conclusions. Mesorhizobium ciceri ND-64 strain with high nitrogen-fixing activity and symbiotic efficiency is capable to synthesize a relatively high amount of extracellular cytokinins. The high concentration of cytokinins indicates their important role in the formation and functioning of nodules, as they stimulate the proliferation of root tissues and, in this way, have a positive effect on the chickpea productivity.
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Nelson, Jessica M., Duncan A. Hauser, José A. Gudiño, Yessenia A. Guadalupe, John C. Meeks, Noris Salazar Allen, Juan Carlos Villarreal, and Fay-Wei Li. "Complete Genomes of Symbiotic Cyanobacteria Clarify the Evolution of Vanadium-Nitrogenase." Genome Biology and Evolution 11, no. 7 (June 27, 2019): 1959–64. http://dx.doi.org/10.1093/gbe/evz137.
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Abstract Plant endosymbiosis with nitrogen-fixing cyanobacteria has independently evolved in diverse plant lineages, offering a unique window to study the evolution and genetics of plant–microbe interaction. However, very few complete genomes exist for plant cyanobionts, and therefore little is known about their genomic and functional diversity. Here, we present four complete genomes of cyanobacteria isolated from bryophytes. Nanopore long-read sequencing allowed us to obtain circular contigs for all the main chromosomes and most of the plasmids. We found that despite having a low 16S rRNA sequence divergence, the four isolates exhibit considerable genome reorganizations and variation in gene content. Furthermore, three of the four isolates possess genes encoding vanadium (V)-nitrogenase (vnf), which is uncommon among diazotrophs and has not been previously reported in plant cyanobionts. In two cases, the vnf genes were found on plasmids, implying possible plasmid-mediated horizontal gene transfers. Comparative genomic analysis of vnf-containing cyanobacteria further identified a conserved gene cluster. Many genes in this cluster have not been functionally characterized and would be promising candidates for future studies to elucidate V-nitrogenase function and regulation.
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Bale, Nicole J., Rick Hennekam, Ellen C. Hopmans, Denise Dorhout, Gert-Jan Reichart, Marcel van der Meer, Tracy A. Villareal, Jaap S. Sinninghe Damsté, and Stefan Schouten. "Biomarker evidence for nitrogen-fixing cyanobacterial blooms in a brackish surface layer in the Nile River plume during sapropel deposition." Geology 47, no. 11 (September 25, 2019): 1088–92. http://dx.doi.org/10.1130/g46682.1.
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Abstract Sapropels are organic-rich sediment layers deposited in the eastern Mediterranean Sea during precession minima, resulting from an increase in export productivity and/or preservation. Increased freshwater delivery from the African continent resulted in stratification, causing deepwater anoxia, while nutrient input stimulated productivity, presumably at the deep chlorophyll maximum. Previous studies have suggested that during sapropel deposition, nitrogen fixation was widespread in the highly stratified surface waters, and that cyanobacteria symbiotic with diatoms (diatom-diazotroph associations, DDAs) were responsible. Here we analyzed sapropel S5 sediments for heterocyst glycolipids (HGs) from three locations in the eastern Mediterranean. HG biomarkers can differentiate between those heterocystous cyanobacteria that are free living (found predominately in freshwater or brackish environments) and those that are from DDAs (found in marine settings). In our primary core, from a location which would have been influenced by the Nile River outflow, we detected a HG with a pentose (C5) head group specific for DDAs. However, HGs with a hexose (C6) head group, specific to free-living cyanobacteria, were present in substantially (up to 60×) higher concentration. These data suggest that at our study location, free-living cyanobacteria were the dominant diazotrophs, rather than DDAs. The C6 HGs increased substantially at the onset of sapropel S5 deposition, suggesting that substantial seasonal cyanobacterial blooms were associated with a brackish surface layer flowing from the Nile into the eastern Mediterranean. Two additional S5 sapropels were analyzed, one also from the Nile delta region and one from the region between Libya and southwestern Crete. Overall, comparison of the HG distribution in the three S5 sapropels provides evidence that all three locations were initially influenced by surface salinities that were sufficiently low to support free-living heterocystous cyanobacteria. While free-living heterocystous cyanobacteria continued to outnumber DDAs during sapropel deposition at the two Nile-influenced sites, DDAs, indicators of persistent marine salinities, were the dominant diazotrophs in the upper part of the sapropel at the more westerly site. These results indicate that N2 fixation by free-living cyanobacteria offers an important additional mechanism to stimulate productivity in regions with strong river discharge during sapropel deposition.
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Barcellos, Fernando Gomes, Pâmela Menna, Jesiane Stefânia da Silva Batista, and Mariangela Hungria. "Evidence of Horizontal Transfer of Symbiotic Genes from a Bradyrhizobium japonicum Inoculant Strain to Indigenous Diazotrophs Sinorhizobium (Ensifer) fredii and Bradyrhizobium elkanii in a Brazilian Savannah Soil." Applied and Environmental Microbiology 73, no. 8 (February 16, 2007): 2635–43. http://dx.doi.org/10.1128/aem.01823-06.
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ABSTRACT The importance of horizontal gene transfer (HGT) in the evolution and speciation of bacteria has been emphasized; however, most studies have focused on genes clustered in pathogenesis and very few on symbiosis islands. Both soybean (Glycine max [L.] Merrill) and compatible Bradyrhizobium japonicum and Bradyrhizobium elkanii strains are exotic to Brazil and have been massively introduced in the country since the early 1960s, occupying today about 45% of the cropped land. For the past 10 years, our group has obtained several isolates showing high diversity in morphological, physiological, genetic, and symbiotic properties in relation to the putative parental inoculant strains. In this study, parental strains and putative natural variants isolated from field-grown soybean nodules were genetically characterized in relation to conserved genes (by repetitive extragenic palindromic PCR using REP and BOX A1R primers, PCR-restriction fragment length polymorphism, and sequencing of the 16SrRNA genes), nodulation, and N2-fixation genes (PCR-RFLP and sequencing of nodY-nodA, nodC, and nifH genes). Both genetic variability due to adaptation to the stressful environmental conditions of the Brazilian Cerrados and HGT events were confirmed. One strain (S 127) was identified as an indigenous B. elkanii strain that acquired a nodC gene from the inoculant B. japonicum. Another one (CPAC 402) was identified as an indigenous Sinorhizobium (Ensifer) fredii strain that received the whole symbiotic island from the B. japonicum inoculant strain and maintained an extra copy of the original nifH gene. The results highlight the strategies that bacteria may commonly use to obtain ecological advantages, such as the acquisition of genes to establish effective symbioses with an exotic host legume.
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Saad, Maged M., Sophie Michalet, Romain Fossou, Marina Putnik‐Delić, Michèle Crèvecoeur, Julien Meyer, Chloé de Malézieux, Gérard Hopfgartner, Ivana Maksimović, and Xavier Perret. "Loss of NifQ Leads to Accumulation of Porphyrins and Altered Metal-Homeostasis in Nitrogen-Fixing Symbioses." Molecular Plant-Microbe Interactions® 32, no. 2 (February 2019): 208–16. http://dx.doi.org/10.1094/mpmi-07-18-0188-r.
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Symbiotic nitrogen fixation between legumes and rhizobia involves a coordinated expression of many plant and bacterial genes as well as finely tuned metabolic activities of micro- and macrosymbionts. In spite of such complex interactions, symbiotic proficiency remains a resilient process, with host plants apparently capable of compensating for some deficiencies in rhizobia. What controls nodule homeostasis is still poorly understood and probably varies between plant species. In this respect, the promiscuous Sinorhizobium (Ensifer) fredii strain NGR234 has become a model to assess the relative contribution of single gene products to many symbioses. Here, we describe how a deletion in nifQ of NGR234 (strain NGRΔnifQ) makes nodules of Vigna unguiculata, V. radiata, and Macroptilium atropurpureum but not of the mimisoid tree Leucaena leucocephala, purple-red. This peculiar dark-nodule phenotype did not necessarily correlate with a decreased proficiency of NGRΔnifQ but coincided with a 20-fold or more accumulation of coproporphyrin III and uroporphyrin III in V. unguiculata nodules. Porphyrin accumulation was not restricted to plant cells infected with bacteroids but also extended to the nodule cortex. Nodule metal-homeostasis was altered but not sufficiently to prevent assembly and functioning of nitrogenase. Although the role of NifQ in donating molybdenum during assembly of nitrogenase cofactor FeMo-co makes it essential in free-living diazotrophs, our results highlight the dispensability of NifQ in many legume species.
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Mora, Yolanda, Rafael Díaz, Carmen Vargas-Lagunas, Humberto Peralta, Gabriela Guerrero, Alejandro Aguilar, Sergio Encarnación, Lourdes Girard, and Jaime Mora. "Nitrogen-Fixing Rhizobial Strains Isolated from Common Bean Seeds: Phylogeny, Physiology, and Genome Analysis." Applied and Environmental Microbiology 80, no. 18 (July 7, 2014): 5644–54. http://dx.doi.org/10.1128/aem.01491-14.
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ABSTRACTRhizobial bacteria are commonly found in soil but also establish symbiotic relationships with legumes, inhabiting the root nodules, where they fix nitrogen. Endophytic rhizobia have also been reported in the roots and stems of legumes and other plants. We isolated several rhizobial strains from the nodules of noninoculated bean plants and looked for their provenance in the interiors of the seeds. Nine isolates were obtained, covering most known bean symbiont species, which belong to theRhizobiumandSinorhizobiumgroups. The strains showed several large plasmids, except for aSinorhizobiumamericanumisolate. Two strains, oneRhizobium phaseoliand oneS. americanumstrain, were thoroughly characterized. Optimal symbiotic performance was observed for both of these strains. TheS. americanumstrain showed biotin prototrophy when subcultured, as well as high pyruvate dehydrogenase (PDH) activity, both of which are key factors in maintaining optimal growth. TheR. phaseolistrain was a biotin auxotroph, did not grow when subcultured, accumulated a large amount of poly-β-hydroxybutyrate, and exhibited low PDH activity. The physiology and genomes of these strains showed features that may have resulted from their lifestyle inside the seeds: stress sensitivity, a ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) complex, a homocitrate synthase (usually present only in free-living diazotrophs), a hydrogenase uptake cluster, and the presence of prophages. We propose that colonization by rhizobia and their presence inPhaseolusseeds may be part of a persistence mechanism that helps to retain and disperse rhizobial strains.
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KENNEDY, I. "Non-symbiotic bacterial diazotrophs in crop-farming systems: can their potential for plant growth promotion be better exploited?" Soil Biology and Biochemistry 36, no. 8 (August 2004): 1229–44. http://dx.doi.org/10.1016/j.soilbio.2004.04.006.
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Pajčin, Ivana, Vanja Vlajkov, Jelena Dodić, Aleksandar Jokić, and Jovana Grahovac. "Biotechnological production of plant inoculants based on nitrogen-fixing bacteria." Journal on Processing and Energy in Agriculture 25, no. 2 (2021): 56–63. http://dx.doi.org/10.5937/jpea25-31071.
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Nitrogen is one of the essential elements for plant growth and development in terms of DNA and protein synthesis. Its main reservoir in nature is the atmosphere; however, inert molecular nitrogen present in the air isn't a suitable nitrogen form for plants' nutrition. Therefore it has to be chemically transformed to NH4 + or NO3 - ion by the process known as biological nitrogen fixation. Nitrogen fixation is carried out by free-living or symbiotic nitrogen-fixing prokaryotes (diazotrophs), including bacteria, archaea and cyanobacteria. In order to be used as plant inoculants for nitrogen fixation, the biomass of these prokaryotes must be produced and formulated appropriately through different biotechnological processes. The aim of this study is to summarize the main aspects of biotechnological production of plant inoculants based on nitrogen-fixing bacteria in terms of upstream processing, cultivation and downstream processing, with a special emphasis on cultivation media composition, cultivation conditions, biomass separation and formulation techniques.
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Sarathambal, C., K. Ilamurugu, L. Srimathi Priya, and K. K. Barman. "A review on weeds as source of novel plant growth promoting microbes for crop improvement." Journal of Applied and Natural Science 6, no. 2 (December 1, 2014): 880–86. http://dx.doi.org/10.31018/jans.v6i2.549.
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In the context of increasing international concern for food security and environmental quality, the use of bioinoculants like diazotrophs and plant growth-promoting rhizobacteria (PGPR) for reducing chemical inputs in agriculture is a potentially important issue. The improvement in agricultural sustainability requires optimal use and management of soil fertility and soil physical properties, where both rely on soil biological processes and soil biodiversity. Biological nitrogen fixation by plant-associated bacteria is eco-friendly and has been effectively exploited for crop plants including legumes. Although associations of rhizobacteria with non-leguminous plants such as grasses have been known for decades, they have been poorly - studied. Weedy grass species normally thrive in adverse conditions and act as potential habitats for the diverse groups of elite bacteria with multiple beneficial characters remains unexplored. A more complete understanding of the diversity and functioning of rhizobacterial microorganisms, especially those that have symbiotic relationships with grass species is of great value for agricultural research and application.
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Maquia, Ivete Sandra Alberto, Paula Fareleira, Isabel Videira e. Castro, Ricardo Soares, Denise R. A. Brito, Aires Afonso Mbanze, Aniceto Chaúque, et al. "The Nexus between Fire and Soil Bacterial Diversity in the African Miombo Woodlands of Niassa Special Reserve, Mozambique." Microorganisms 9, no. 8 (July 22, 2021): 1562. http://dx.doi.org/10.3390/microorganisms9081562.
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(1) Background: the Miombo woodlands comprise the most important vegetation from southern Africa and are dominated by tree legumes with an ecology highly driven by fires. Here, we report on the characterization of bacterial communities from the rhizosphere of Brachystegia boehmii in different soil types from areas subjected to different regimes. (2) Methods: bacterial communities were identified through Illumina MiSeq sequencing (16S rRNA). Vigna unguiculata was used as a trap to capture nitrogen-fixing bacteria and culture-dependent methods in selective media were used to isolate plant growth promoting bacteria (PGPB). PGP traits were analysed and molecular taxonomy of the purified isolates was performed. (3) Results: Bacterial communities in the Miombo rhizosphere are highly diverse and driven by soil type and fire regime. Independent of the soil or fire regime, the functional diversity was high, and the different consortia maintained the general functions. A diverse pool of diazotrophs was isolated, and included symbiotic (e.g., Mesorhizobium sp., Neorhizobium galegae, Rhizobium sp., and Ensifer adhaerens), and non-symbiotic (e.g., Agrobacterium sp., Burkholderia sp., Cohnella sp., Microvirga sp., Pseudomonas sp., and Stenotrophomonas sp.) bacteria. Several isolates presented cumulative PGP traits. (4) Conclusions: Although the dynamics of bacterial communities from the Miombo rhizosphere is driven by fire, the maintenance of high levels of diversity and functions remain unchanged, constituting a source of promising bacteria in terms of plant-beneficial activities such as mobilization and acquisition of nutrients, mitigation of abiotic stress, and modulation of plant hormone levels.
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Kozar, S. F. "PRODUCTION OF PHYTOHORMONES OF BRADYRHIZOBIUM JAPONICUM AND AZOSPIRILLUM BRASILENSE UNDER THEIR SIMULTANEOUS CULTIVATION." Agriciltural microbiology 28 (July 10, 2018): 33–40. http://dx.doi.org/10.35868/1997-3004.28.33-40.
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Objective. Investigate the activity of biosynthesis of phytohormonal substances with nitrogen-fixing bacteria Bradyrhizobium japonicum and Azospirillum brasilense in pure and mixed culture.
Methods. Microbiological, chromatographic, and mathematical.
Results It has been established that the simultaneous cultivation of B. japonicum M-8 and A. brasilense 410 increases the content of gibberellins and cytokinins in the culture fluid of the test microorganisms. The content of gibberellic acid and isopentenylidene has increased most intensively in mixed culture compared with the pure culture of rhizobia. In the course of co-cultivation, the studied diazotrophs more intensively produced auxins compared to soybean rhizobia in pure culture, but less compared to pure culture of azospirilla. The highest level of abscisic acid that can inhibit the formation of nodules was found in A. brasilense 410 culture fluid, and it was lower when cultivating B japonicum M-8. However, the smallest amount of this phytohormone was found in the culture liquid of diazotrophs under their co-cultivation. The lowest ratio of auxin/cytokinin was found in B. japonicum M-8 and A. brasilense 410 culture fluid under their co-cultivation, which should positively influence the formation of a symbiotic system when interacting with soybean plants.
Conclusion. A combination of cultivating rhizobia and azospirilla showed an increase in the amount of cytokinins and gibberellins in the culture fluid of the microorganisms, a decrease in the amount of abscisic acid and improvement in the auxin/cytokinin ratio compared to the values of the pure cultures of the nitrogen-fixing bacteria studied. An analysis of the quantitative parameters of the content of phytohormones suggests the feasibility of combining B. japonicum and A. brasilense in a mixed culture for the effective introduction of rhizobia in soybean agrocenosis.
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Kyrychenko, O. V., S. V. Omelchuk, and A. V. Khrapova. "Realization of Nodulation and Nitrogen-Fixing Activities of Bradyrhizobium japonicum and Rhizosphere Microbiota through Seed Treatment with Pesticide Standak Top and Spraying Plants with Soybean Seed Lectin." Mikrobiolohichnyi Zhurnal 84, no. 6 (February 28, 2023): 26–37. http://dx.doi.org/10.15407/microbiolj84.06.026.
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The idea of the study was to use soybean lectin as a biologically active compound with a broad spectrum of action to spray soybean plants for stabilization of the formation and functioning of the soybean-rhizobium symbiosis as well as the nitrogen-fixing activity of rhizosphere microbiota against the background of seed treatment with chemical plant protection product Standak Top — an innovative pesticide with fungicidal and insecticidal activity for the control of major diseases and pests of soybean plants. Aim. To study the peculiarities of formation and functioning of soybean-rhizobium symbiosis as well as the nitrogen-fixing activity of rhizosphere microbiota under spraying plants with specific soybean seed lectin on the background of seed treatment with Standak Top and inoculation with nodule bacteria Bradyrhizobium japonicum 634b on the sowing day in the conditions of pot experiments with soil as a substrate. Methods. Physiological, microbiological, gas chromatography, and statistical methods were used. Results. It was shown that after seed treatment with Standak Top (1.5 L/ton of seeds) on the sowing day, there was observed suppression of the process of nodule formation on the roots in the period of soybean vegetative growth. The nitrogen-fixing activity of the symbiotic system was at the control level, while the functional activity of soil diazotrophs was suppressed (by 1.2—2.2 times). Spraying plants in the phase of two trifoliate leaves (V2) with soybean seed lectin (without pesticide) led to an increase in the total mass of nodules on the plant (by 1.5 and 1.9 times as well as by 2.3 and 2.0 times compared to the control of inoculation in the phase of three trifoliate leaves (V3) and beginning of pod formation (R3), respectively). The increase in the total mass of the symbiotic apparatus on soybean roots in the phases V3 and R3 respectively was by 1.4 and 1.5 times in comparison with seed treatment with Standak Top, and the mass of one nodule was higher by 1.3 and 1.6 times, respectively. Soybean seed lectin led to a signifi cant increase in the actual nitrogenase activity of the soybean-rhizobium symbiosis. It was 2.9 and 1.9 times higher compared to control of inoculation and 2.1 and 1.8 times compared to the variant of inoculation + pesticide in the V3 and R3 phases, respectively. The functional activity of soil nitrogen-fixing microorganisms did not change significantly. The use of soybean seed lectin against the background of the seed treatment with Standak Top and inoculation contributed to the stabilization and increase in the rhizobia nodulation ability, the suppression of which was due to the infl uence of such an anthropogenic factor as pesticides. Th ere was observed an increase in the number (by 1.6 and 1.2 times) and mass of root nodules (by 2.2 and 1.5 times and 1.4 and 1.2 times, respectively, compared to the controls of inoculation and inoculation + pesticide). Soybean seed lectin significantly increased the nitrogenase activity of the symbiosis against the background of Standak Top (by 1.9 and 1.6 times and 1.4 and 1.5 times, respectively, in the V3 and R3 phases of soybean ontogenesis) compared to the control of inoculation and inoculation + Standak Top. Conclusions. The obtained results suggest the possibility of using the method of spraying plants with specific lectin as a means of leveling (or mitigating) the negative effect of pesticides used for the seed treatment on the formation and functioning of the symbiosis and rhizosphere diazotrophic microbiota. This indicates the prospects of studying the biological activity of phytolectins in spraying plants in order to regulate the formation and functioning of phytobacterial systems, as well as their responses to various environmental or anthropogenic stress factors, in particular, to the effect of chemical plant-protecting products used for the seed treatment.
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Sangsawang, Laddawan, Beatriz Estela Casareto, Hideo Ohba, Hung Manh Vu, Aussanee Meekaew, Toshiyuki Suzuki, Thamasak Yeemin, and Yoshimi Suzuki. "13 C and 15 N assimilation and organic matter translocation by the endolithic community in the massive coral Porites lutea." Royal Society Open Science 4, no. 12 (December 2017): 171201. http://dx.doi.org/10.1098/rsos.171201.
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Corals evolved by establishing symbiotic relationships with various microorganisms (the zooxanthellae, filamentous algae, cyanobacteria, bacteria, archaea, fungi and viruses), forming the ‘coral holobiont'. Among them, the endolithic community is the least studied. Its main function was considered to be translocation of photo-assimilates to the coral host, particularly during bleaching. Here, we hypothesize that (i) endolithic algae may show similar primary production rates in healthy or bleached corals by changing their pigment ratios, and therefore that similar production and translocation of organic matter may occur at both conditions and (ii) diazotrophs are components of the endolithic community; therefore, N 2 fixation and translocation of organic nitrogen may occur. We tested these hypotheses in incubation of Porites lutea with 13 C and 15 N tracers to measure primary production and N 2 fixation in coral tissues and endoliths. Assimilation of the 13 C atom (%) was observed in healthy and bleached corals when the tracer was injected in the endolithic band, showing translocation in both conditions. N 2 fixation was found in coral tissues and endolithic communities with translocation of organic nitrogen. Thus, the endolithic community plays an important role in supporting the C and N metabolism of the holobiont, which may be crucial under changing environmental conditions.
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Schogolev, A. S., and I. M. Raievska. "Role of nitrogen deficiency on growth and development near isogenic by E genes lines of soybean co-inoculated with nitrogen-fixing bacteria." Regulatory Mechanisms in Biosystems 12, no. 2 (May 16, 2021): 326–34. http://dx.doi.org/10.15421/022144.
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Nitrogen deficiency is a limiting factor in increasing efficiency of crop production in terrestrial ecosystems, and the transformation of inert nitrogen to forms that can be assimilated by plants is mediated by soil microorganisms. Symbiotic nitrogen-fixing bacteria and roots depend on each other and have developed various mechanisms for symbiotic coexistence. The aim of this work was to investigate the role of nitrogen deficiency on growth and development near isogenic by E genes lines of soybean (Glycine max (L.) Merr.): short-day (SD) line with genotype Е1е2е3(Е4е5Е7), and photoperiodic insensitive (PPI) line with genotype е1е2е3(Е4е5Е7) grown from seeds inoculated with active strains of Bradyrhizobium japonicum against the background of local populations of diazotrophs of the genus Azotobacter spp. and establish how the soybean – Bradyrhizobium symbiosis will develop as the genes of both microsymbionts and macrosymbionts are responsible for the formation of the symbiotic complex. Plants were grown in a vegetation chamber, in sand culture. To assess the quantitative composition of microorganisms in the rhizosphere and rhizoplanes, 6 plants were selected from each soybean line, then separation of the zones of the rhizosphere and rhizoplanes was performed using the method of washing and the resulting suspension was used for inoculation on dense nutrient media (mannitol-yeast agar medium and Ashby medium). The results of study showed that seed inoculation and co-inoculation provides faster formation of the symbiotic soybean – Bradyrhizobium complex. Differences in nodulation rates between the short-day line with genotype Е1е2е3(Е4е5Е7), and a photoperiodic insensitive line with genotype е1е2е3(Е4е5Е7) were identified. Determination of the amount of B. japonicum on the medium of mannitol-yeast agar in the rhizosphere and rhizoplane showed that inoculation by B. japonicum strain 634b caused a significant increase in the amount B. japonicum in the rhizosphere and rhizoplane in both soybean lines, comparison with non-inoculated seeds. Then, co-inoculation by B. japonicum strain 634b + Azotobacter chroococcum significantly increased the amount of B. japonicum only in the rhizoplane and decreased their number in the rhizosphere. Determination of the amount of A. chroococcum on the Ashby elective medium in the rhizosphere and rhizoplane showed that the inoculation by B. japonicum strain 634b caused a significant decrease in the amount of A. chroococcum both in the rhizosphere and in the rhizoplane of the PPI line of soybean, and in the rhizosphere the SD line, in comparison with non-inoculated seeds. That can testify to the competitive interaction of these microorganisms. However, the co-inoculation by B. japonicum strain 634b + A. chroococcum in the SD line significantly increased the number of A. chroococcum in the rhizoplane and decreased their number in the rhizosphere, in the PPI line their number decreased in the rhizoplane and increased in the rhizosphere, in comparison with non-inoculated seeds. Probably, the E genes (their dominant or recessive state) of soybean isogenic lines affect the regulation of the content and distribution of sugars. It was established that the nitrogen deficiency stimulated development of the root system of plants and the synthesized sugars were distributed predominantly to the root system growth. We suppose that the seeds’ inoculation had extended sugar consumption to the symbiont, due to which it compensates the lack of nitrogen, but leads to a slower growth of the root system.
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Rui, Junpeng, Jingjing Hu, Fuxin Wang, Yuwei Zhao, and Chao Li. "Altitudinal niches of symbiotic, associative and free-living diazotrophs driven by soil moisture and temperature in the alpine meadow on the Tibetan Plateau." Environmental Research 211 (August 2022): 113033. http://dx.doi.org/10.1016/j.envres.2022.113033.
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Kariman, Khalil, Benjamin Moreira-Grez, Craig Scanlan, Saleh Rahimlou, Gustavo Boitt, and Zed Rengel. "Synergism between feremycorrhizal symbiosis and free-living diazotrophs leads to improved growth and nutrition of wheat under nitrogen deficiency conditions." Biology and Fertility of Soils 58, no. 2 (January 7, 2022): 121–33. http://dx.doi.org/10.1007/s00374-021-01616-7.
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AbstractA controlled-environment study was conducted to explore possible synergistic interactions between the feremycorrhizal (FM) fungus Austroboletus occidentalis and soil free-living N2-fixing bacteria (diazotrophs). Wheat (Triticum aestivum) plants were grown under N deficiency conditions in a field soil without adding microbial inoculum (control: only containing soil indigenous microbes), or inoculated with a consortium containing four free-living diazotroph isolates (diazotrophs treatment), A. occidentalis inoculum (FM treatment), or both diazotrophs and A. occidentalis inoculums (dual treatment). After 7 weeks of growth, significantly greater shoot biomass was observed in plants inoculated with diazotrophs (by 25%), A. occidentalis (by 101%), and combined inoculums (by 106%), compared to the non-inoculated control treatment. All inoculated plants also had higher shoot nutrient contents (including N, P, K, Mg, Zn, Cu, and Mn) than the control treatment. Compared to the control and diazotrophs treatments, significantly greater shoot N content was observed in the FM treatment (i.e., synergism between the FM fungus and soil indigenous diazotrophs). Dually inoculated plants had the highest content of nutrients in shoots (e.g., N, P, K, S, Mg, Zn, Cu, and Mn) and soil total N (13–24% higher than the other treatments), i.e., synergism between the FM fungus and added diazotrophs. Root colonization by soil indigenous arbuscular mycorrhizal fungi declined in all inoculated plants compared to control. Non-metric multidimensional scaling (NMDS) analysis of the bacterial 16S rRNA gene amplicons revealed that the FM fungus modified the soil microbiome. Our in vitro study indicated that A. occidentalis could not grow on substrates containing lignocellulosic materials or sucrose, but grew on media supplemented with hexoses such as glucose and fructose, indicating that the FM fungus has limited saprotrophic capacity similar to ectomycorrhizal fungi. The results revealed synergistic interactions between A. occidentalis and soil free-living diazotrophs, indicating a potential to boost microbial N2 fixation for non-legume crops.
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Abo-Koura, Hanaa A. "Endophytic Bacteria; Diversity, Characterization and Role in Agriculture." Journal of Basic & Applied Sciences 19 (August 7, 2023): 116–30. http://dx.doi.org/10.29169/1927-5129.2023.19.11.
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Entophytic bacteria have an important role in the growth process and health of the plant host. Nevertheless, also some endophytic bacteria are existing in seeds and have not been studied yet. In addition, some Entophytic bacteria are important in plant tolerance to environmental stresses. They can colonize the internal tissues of the host and are able to use a variety of different relations including symbiotic, mutualism, communalistic, and trophobiotic. They have the ability for plant hormone production like auxin, indole acetic acid, and gibberellin; also some endophytic bacteria have the ability for siderophore creation, phosphate solubilization, nitrogen fixation, protease, and hydrogen cyanide formation.. Moreover, they produce compounds that could have possible usage in drug, agriculture or engineering. They have the ability to removesoil toxins thus, improving phytoremediation and soil fertility. Further, most of endophytic bacteria are diazotrophs and associated with the Proteobacteria, and a varied range has been detected agreeing to the nifH gene which codes for nitrogenase enzyme, structures recovered from plant materials, however a limited part of these genes looks to be stated. The endophytes discussed in this review are isolated from surface-disinfested plant tissue, and that do not damage the plant. Moreover, endophytes appear to be in-between saprophytic bacteria and plant pathogens, they are either saprophytes growing to be pathogens, or extremely grown plant pathogens with protective accommodation and nutrient provisions, but not killing their host. Generally, endophytic bacteria are partial under biotic and abiotic influences, with the plant itself being one of the main prompting influences.
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Llamas, Angel, Esperanza Leon-Miranda, and Manuel Tejada-Jimenez. "Microalgal and Nitrogen-Fixing Bacterial Consortia: From Interaction to Biotechnological Potential." Plants 12, no. 13 (June 28, 2023): 2476. http://dx.doi.org/10.3390/plants12132476.
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Microalgae are used in various biotechnological processes, such as biofuel production due to their high biomass yields, agriculture as biofertilizers, production of high-value-added products, decontamination of wastewater, or as biological models for carbon sequestration. The number of these biotechnological applications is increasing, and as such, any advances that contribute to reducing costs and increasing economic profitability can have a significant impact. Nitrogen fixing organisms, often called diazotroph, also have great biotechnological potential, mainly in agriculture as an alternative to chemical fertilizers. Microbial consortia typically perform more complex tasks than monocultures and can execute functions that are challenging or even impossible for individual strains or species. Interestingly, microalgae and diazotrophic organisms are capable to embrace different types of symbiotic associations. Certain corals and lichens exhibit this symbiotic relationship in nature, which enhances their fitness. However, this relationship can also be artificially created in laboratory conditions with the objective of enhancing some of the biotechnological processes that each organism carries out independently. As a result, the utilization of microalgae and diazotrophic organisms in consortia is garnering significant interest as a potential alternative for reducing production costs and increasing yields of microalgae biomass, as well as for producing derived products and serving biotechnological purposes. This review makes an effort to examine the associations of microalgae and diazotrophic organisms, with the aim of highlighting the potential of these associations in improving various biotechnological processes.
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Ma’ruf, Amar, Syahminar Syahminar, and Cik Zulia. "A Comprehensive Process Of Nitrogen Fixation In Plants." Jurnal Agrium 20, no. 4 (December 14, 2023): 299. http://dx.doi.org/10.29103/agrium.v20i4.13994.
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Nitrogen is a component of several biomolecules that are essential for all organisms' growth and development. Nitrogen fixation is the biological process that converts molecular nitrogen to ammonia. Biological nitrogen fixation is mediated by diazotroph microorganisms that use nitrogenase enzymes to enhance atmospheric nitrogen. Much of this is accomplished through a symbiotic interaction between plants and diazotrophic bacteria. Microbiology and plant biology are discussed in symbiotic nitrogen fixation discussions. Some of the nitrogen fixation mechanisms mentioned in this paper begin with the formation of nodules, the action of the nitrogenase enzyme in reducing nitrogen to ammonia, and the presence of rhizobia in nodules. This study provides a comprehensive overview of the nodule formation process, the role of the nitrogenase enzyme in reducing nitrogen to ammonia, and the presence of rhizobia in nodules. A more complete literature review on biological nitrogen fixing in plants is required to obtain more specific information.
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Gu, Benguo, Yi Chen, Fang Xie, Jeremy D. Murray, and Anthony J. Miller. "Inorganic Nitrogen Transport and Assimilation in Pea (Pisum sativum)." Genes 13, no. 1 (January 17, 2022): 158. http://dx.doi.org/10.3390/genes13010158.
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The genome sequences of several legume species are now available allowing the comparison of the nitrogen (N) transporter inventories with non-legume species. A survey of the genes encoding inorganic N transporters and the sensing and assimilatory families in pea, revealed similar numbers of genes encoding the primary N assimilatory enzymes to those in other types of plants. Interestingly, we find that pea and Medicago truncatula have fewer members of the NRT2 nitrate transporter family. We suggest that this difference may result from a decreased dependency on soil nitrate acquisition, as legumes have the capacity to derive N from a symbiotic relationship with diazotrophs. Comparison with M. truncatula, indicates that only one of three NRT2s in pea is likely to be functional, possibly indicating less N uptake before nodule formation and N-fixation starts. Pea seeds are large, containing generous amounts of N-rich storage proteins providing a reserve that helps seedling establishment and this may also explain why fewer high affinity nitrate transporters are required. The capacity for nitrate accumulation in the vacuole is another component of assimilation, as it can provide a storage reservoir that supplies the plant when soil N is depleted. Comparing published pea tissue nitrate concentrations with other plants, we find that there is less accumulation of nitrate, even in non-nodulated plants, and that suggests a lower capacity for vacuolar storage. The long-distance transported form of organic N in the phloem is known to be specialized in legumes, with increased amounts of organic N molecules transported, like ureides, allantoin, asparagine and amides in pea. We suggest that, in general, the lower tissue and phloem nitrate levels compared with non-legumes may also result in less requirement for high affinity nitrate transporters. The pattern of N transporter and assimilatory enzyme distribution in pea is discussed and compared with non-legumes with the aim of identifying future breeding targets.
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Machray, G. C., and W. D. P. Stewart. "Genetics of plant-microbe nitrogen-fixing symbiosis." Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 85, no. 3-4 (1985): 239–52. http://dx.doi.org/10.1017/s0269727000004048.
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SynopsisA wide variety of plant-microbe nitrogen-fixing symbioses which include cyanobacteria as the nitrogenfixing partner exist. While some information has been gathered on the biochemical changes in the cyanobacterium upon entering into symbiosis, very little is known about the accompanying changes at the genetic level. Much of our present knowledge of the organisation and control of expression of nitrogenfixation (nif) genes is derived from studies of the free-living diazotroph Klebsiella pneumoniae. This organism thus provides a model system and source of experimental material for the genetic analysis of symbiotic nitrogen fixation. We describe the use of cloned K. pneumoniae genes for nitrogen fixation and its regulation in the genetic analysis' of nitrogen fixation in cyanobacteria which can enter into symbiosis with plants. These studies reveal some dissimilarities in the organisation of nif genes and raise questions as to the genetic control of nitrogen fixation in symbiosis.
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van den Elzen, Eva, Martine A. R. Kox, Sarah F. Harpenslager, Geert Hensgens, Christian Fritz, Mike S. M. Jetten, Katharina F. Ettwig, and Leon P. M. Lamers. "Symbiosis revisited: phosphorus and acid buffering stimulate N<sub>2</sub> fixation but not <i>Sphagnum</i> growth." Biogeosciences 14, no. 5 (March 9, 2017): 1111–22. http://dx.doi.org/10.5194/bg-14-1111-2017.
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Abstract. In pristine Sphagnum-dominated peatlands, (di)nitrogen (N2) fixing (diazotrophic) microbial communities associated with Sphagnum mosses contribute substantially to the total nitrogen input, increasing carbon sequestration. The rates of symbiotic nitrogen fixation reported for Sphagnum peatlands, are, however, highly variable, and experimental work on regulating factors that can mechanistically explain this variation is largely lacking. For two common fen species (Sphagnum palustre and S. squarrosum) from a high nitrogen deposition area (25 kg N ha−1 yr−1), we found that diazotrophic activity (as measured by 15 − 15N2 labeling) was still present at a rate of 40 nmol N gDW−1 h−1. This was surprising, given that nitrogen fixation is a costly process. We tested the effects of phosphorus availability and buffering capacity by bicarbonate-rich water, mimicking a field situation in fens with stronger groundwater or surface water influence, as potential regulators of nitrogen fixation rates and Sphagnum performance. We expected that the addition of phosphorus, being a limiting nutrient, would stimulate both diazotrophic activity and Sphagnum growth. We indeed found that nitrogen fixation rates were doubled. Plant performance, in contrast, did not increase. Raised bicarbonate levels also enhanced nitrogen fixation, but had a strong negative impact on Sphagnum performance. These results explain the higher nitrogen fixation rates reported for minerotrophic and more nutrient-rich peatlands. In addition, nitrogen fixation was found to strongly depend on light, with rates 10 times higher in light conditions suggesting high reliance on phototrophic organisms for carbon. The contrasting effects of phosphorus and bicarbonate on Sphagnum spp. and their diazotrophic communities reveal strong differences in the optimal niche for both partners with respect to conditions and resources. This suggests a trade-off for the symbiosis of nitrogen fixing microorganisms with their Sphagnum hosts, in which a sheltered environment apparently outweighs the less favorable environmental conditions. We conclude that microbial activity is still nitrogen limited under eutrophic conditions because dissolved nitrogen is being monopolized by Sphagnum. Moreover, the fact that diazotrophic activity can significantly be upregulated by increased phosphorus addition and acid buffering, while Sphagnum spp. do not benefit, reveals remarkable differences in optimal conditions for both symbiotic partners and calls into question the regulation of nitrogen fixation by Sphagnum under these eutrophic conditions. The high nitrogen fixation rates result in high additional nitrogen loading of 6 kg ha−1 yr−1 on top of the high nitrogen deposition in these ecosystems.
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Gao, Meng, Gabrielle Armin, and Keisuke Inomura. "Low-Ammonium Environment Increases the Nutrient Exchange between Diatom–Diazotroph Association Cells and Facilitates Photosynthesis and N2 Fixation—a Mechanistic Modeling Analysis." Cells 11, no. 18 (September 17, 2022): 2911. http://dx.doi.org/10.3390/cells11182911.
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Diatom–diazotroph associations (DDAs) are one of the most important symbiotic dinitrogen (N2) fixing groups in the oligotrophic ocean. Despite their capability to fix N2, ammonium (NH4+) remains a key nitrogen (N) source for DDAs, and the effect of NH4+ on their metabolism remains elusive. Here, we developed a coarse-grained, cellular model of the DDA with NH4+ uptake and quantified how the level of extracellular NH4+ influences metabolism and nutrient exchange within the symbiosis. The model shows that, under a fixed growth rate, an increased NH4+ concentration may lower the required level of N2 fixation and photosynthesis, and decrease carbon (C) and N exchange. A low-NH4+ environment leads to more C and N in nutrient exchange and more fixed N2 to support a higher growth rate. With higher growth rates, nutrient exchange and metabolism increased. Our study shows a strong effect of NH4+ on metabolic processes within DDAs, and thus highlights the importance of in situ measurement of NH4+ concentrations.
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de Oliveira Cunha, Cláudio, Luiz Fernando Goda Zuleta, Luiz Gonzaga Paula de Almeida, Luciane Prioli Ciapina, Wardsson Lustrino Borges, Rosa Maria Pitard, José Ivo Baldani, et al. "Complete Genome Sequence of Burkholderia phenoliruptrix BR3459a (CLA1), a Heat-Tolerant, Nitrogen-Fixing Symbiont of Mimosa flocculosa." Journal of Bacteriology 194, no. 23 (November 9, 2012): 6675–76. http://dx.doi.org/10.1128/jb.01821-12.
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ABSTRACTThe genusBurkholderiarepresents a challenge to the fields of taxonomy and phylogeny and, especially, to the understanding of the contrasting roles as either opportunistic pathogens or bacteria with biotechnological potential. Few genomes of nonpathogenic strains, especially of diazotrophic symbiotic bacteria, have been sequenced to improve understanding of the genus. Here, we contribute with the complete genome sequence ofBurkholderia phenoliruptrixstrain BR3459a (CLA1), an effective diazotrophic symbiont of the leguminous treeMimosa flocculosaBurkart, which is endemic to South America.
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Waraczewska, Zyta, Alicja Niewiadomska, Agnieszka Wolna-Maruwka, Hanna Sulewska, Anna Budka, and Agnieszka A. Pilarska. "The Effect of In Vitro Coinoculation on the Physiological Parameters of White Lupine Plants (Lupinus albus L.)." Applied Sciences 12, no. 23 (December 3, 2022): 12382. http://dx.doi.org/10.3390/app122312382.
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The aim of the study was to select microbiological inoculants for a specific plant species, i.e., white lupine (Lupinus albus L.), to increase the efficiency of the diazotroph process. The research involved an in vitro assessment of interactions between the symbiotic bacteria (Bradyrhizobium sp. isolated from Nitragina and Nitroflora commercial preparations dedicated to white lupine) and selected endophytes (Pseudomonas fluorescens or Bacillus subtilis) used for seed coinoculation. In addition, selected morphological traits of plants (the weight and length of aboveground and belowground parts) were examined after the inoculation/coinoculation. The degree of root colonisation by selected endophytes used as individual inoculants and in combination with bacteria of the Bradyrhizobium genus was determined. The diazotrophic parameters were also investigated (nitrogenase activity, the number, and weight of nodules). The results showed no antagonistic interactions have been demonstrated between bacterial strains of the genus Bradyrhizobium sp. isolated from Nitragina and Nitroflora, and the endophytes Pseudomonas fluorescens or Bacillus subtilis used for the study. The applied coinoculation in vitro had a stimulating effect on the weight of the stems and roots of white lupine causing an average increase of 13% and 28%, respectively. The level of nitrogenase activity in the coinoculation variants increased from 3.5 nMC2H4 plant−1 h−1 to an average of 32.34 nMC2H4 plant−1 h−1.
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Kyrychenko, О. V. "SYMBIOTIC PRODUCTIVITY OF PHYTO-BACTERIAL SYSTEMS UNDER THE ACTION OF N-ACETYL-D-GLUCOSAMINE ON DIAZOTROPHIC MICROORGANISMS." Biotechnologia Acta 13, no. 1 (February 2020): 15–29. http://dx.doi.org/10.15407/biotech13.01.015.
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Estrada-de los Santos, Paulina, Marike Palmer, Belén Chávez-Ramírez, Chrizelle Beukes, Emma Steenkamp, Leah Briscoe, Noor Khan, et al. "Whole Genome Analyses Suggests that Burkholderia sensu lato Contains Two Additional Novel Genera (Mycetohabitans gen. nov., and Trinickia gen. nov.): Implications for the Evolution of Diazotrophy and Nodulation in the Burkholderiaceae." Genes 9, no. 8 (August 1, 2018): 389. http://dx.doi.org/10.3390/genes9080389.
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Burkholderia sensu lato is a large and complex group, containing pathogenic, phytopathogenic, symbiotic and non-symbiotic strains from a very wide range of environmental (soil, water, plants, fungi) and clinical (animal, human) habitats. Its taxonomy has been evaluated several times through the analysis of 16S rRNA sequences, concantenated 4–7 housekeeping gene sequences, and lately by genome sequences. Currently, the division of this group into Burkholderia, Caballeronia, Paraburkholderia, and Robbsia is strongly supported by genome analysis. These new genera broadly correspond to the various habitats/lifestyles of Burkholderia s.l., e.g., all the plant beneficial and environmental (PBE) strains are included in Paraburkholderia (which also includes all the N2-fixing legume symbionts) and Caballeronia, while most of the human and animal pathogens are retained in Burkholderia sensu stricto. However, none of these genera can accommodate two important groups of species. One of these includes the closely related Paraburkholderia rhizoxinica and Paraburkholderia endofungorum, which are both symbionts of the fungal phytopathogen Rhizopus microsporus. The second group comprises the Mimosa-nodulating bacterium Paraburkholderia symbiotica, the phytopathogen Paraburkholderia caryophylli, and the soil bacteria Burkholderia dabaoshanensis and Paraburkholderia soli. In order to clarify their positions within Burkholderia sensu lato, a phylogenomic approach based on a maximum likelihood analysis of conserved genes from more than 100 Burkholderia sensu lato species was carried out. Additionally, the average nucleotide identity (ANI) and amino acid identity (AAI) were calculated. The data strongly supported the existence of two distinct and unique clades, which in fact sustain the description of two novel genera Mycetohabitans gen. nov. and Trinickia gen. nov. The newly proposed combinations are Mycetohabitans endofungorum comb. nov., Mycetohabitansrhizoxinica comb. nov., Trinickia caryophylli comb. nov., Trinickiadabaoshanensis comb. nov., Trinickia soli comb. nov., and Trinickiasymbiotica comb. nov. Given that the division between the genera that comprise Burkholderia s.l. in terms of their lifestyles is often complex, differential characteristics of the genomes of these new combinations were investigated. In addition, two important lifestyle-determining traits—diazotrophy and/or symbiotic nodulation, and pathogenesis—were analyzed in depth i.e., the phylogenetic positions of nitrogen fixation and nodulation genes in Trinickia via-à-vis other Burkholderiaceae were determined, and the possibility of pathogenesis in Mycetohabitans and Trinickia was tested by performing infection experiments on plants and the nematode Caenorhabditis elegans. It is concluded that (1) T. symbiotica nif and nod genes fit within the wider Mimosa-nodulating Burkholderiaceae but appear in separate clades and that T. caryophyllinif genes are basal to the free-living Burkholderia s.l. strains, while with regard to pathogenesis (2) none of the Mycetohabitans and Trinickia strains tested are likely to be pathogenic, except for the known phytopathogen T. caryophylli.
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Kozar, S. F., and T. O. Usmanova. "REGULATION OF GROWTH ACTIVITY OF POPULATION OF INDUSTRIAL BRADYRHIZOBIUM JAPONICUM STRAINS IN VITRO." Agriciltural microbiology 7 (October 23, 2008): 36–47. http://dx.doi.org/10.35868/1997-3004.7.36-47.
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The results of researches on optimization of soya rhizobium cultivation process through choosing optimum environments are shown in the article. It also represents growth activity of Bradyrhizobium japonicum population influenced by products of symbiotic and associative diazotroph metabolism in vitro. The highest growth activity of these microorganisms is shown when their cultivation in the medium with sterile bacterial suspensions with exo- and endo- metabolites of Azospirillum brasilense.
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Horak, Rachel E. A., and Joseph P. Montoya. "Growth, nitrogen fixation, respiration, and a nitrogen budget for cultures of a cosmopolitan diazotrophic endosymbiont (Teredinibacter turnerae) of shipworms." Journal of the Marine Biological Association of the United Kingdom 94, no. 1 (November 7, 2013): 177–85. http://dx.doi.org/10.1017/s0025315413001483.
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Wood-boring bivalves (Bivalvia, family Teredinidae), also known as shipworms, host dinitrogen-fixing and cellulolytic symbiotic bacteria in gill bacteriocytes, which may be a necessary adaptation to a wooden diet. Although oxygen (O2) inhibits nitrogenase in other species, symbionts are able to fix nitrogen (N) within the gill tissue and provide newly fixed N to the host shipworm. The recent direct evidence of new N incorporation into the host tissue indicates that there are potentially complex nutrient cycles in this symbiosis and uninvestigated controls upon these cycles.To elucidate the mechanisms of this unique N2-fixing symbiosis and determine whether symbionts can excrete newly fixed N, we measured rates of growth, N2-fixation, respiration, and inorganic N content for the cultivated symbiontTeredinibacter turnerae(γ-proteobacteria, strain T7901) under a range of headspace O2conditions. In all conditions, headspace O2did not affect maximum specific N2-fixation and respiration activity, but did influence the rate and timing of growth. These results are consistent with the development of microaerobic conditions through an oxygen gradient in the culture medium, which facilitates N2-fixation and growth. The medium accumulated a small amount of NH4+, which represented 0.5–2.5% of the total N fixed by the culture. We constructed a simple N budget forT. turneraeto assess the role of the major known N sources and sinks. The N budget was not closed, indicating that new N is allocated to currently unidentified sinks, which may include excreted dissolved organic nitrogen.
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Jabir, T., V. Dhanya, Y. Jesmi, M. P. Prabhakaran, N. Saravanane, G. V. M. Gupta, and A. A. M. Hatha. "Occurrence and Distribution of a Diatom-Diazotrophic Cyanobacteria Association during a Trichodesmium Bloom in the Southeastern Arabian Sea." International Journal of Oceanography 2013 (August 6, 2013): 1–6. http://dx.doi.org/10.1155/2013/350594.
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Symbiotic diatom-diazotrophic cyanobacteria association (DDA) of Rhizosolenia hebetata and Rhizosolenia formosa with endosymbiotic cyanobacteria Richelia intracellularis was noticed and documented for the first time during a bloom of the cyanobacterium Trichodesmium erythraeum in the oligotrophic shelf waters along Kochi and Mangalore transects, southeastern Arabian Sea (SEAS), during spring intermonsoon (April 2012). Although the host is frequently seen, the symbiont is rarely reported in the Indian EEZ. The presence of nitrogen-fixing symbiotic association of Rhizosolenia-Richelia along with Trichodesmium erythraeum highlights the significance of DDAs on the nutrient and energy budgets of phytoplankton in the oligotrophic environments of the Arabian Sea during spring intermonsoon.
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Martínez, Marta, José M. Palacios, Juan Imperial, and Tomás Ruiz-Argüeso. "Symbiotic Autoregulation of nifA Expression in Rhizobium leguminosarum bv. viciae." Journal of Bacteriology 186, no. 19 (October 1, 2004): 6586–94. http://dx.doi.org/10.1128/jb.186.19.6586-6594.2004.
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ABSTRACT NifA is the general transcriptional activator of nitrogen fixation genes in diazotrophic bacteria. In Rhizobium leguminosarum bv. viciae UPM791, the nifA gene is part of a gene cluster (orf71 orf79 fixW orf5 fixABCX nifAB) separated by 896 bp from an upstream and divergent truncated duplication of nifH (ΔnifH). Symbiotic expression analysis of genomic nifA::lacZ fusions revealed that in strain UPM791 nifA is expressed mainly from a σ54-dependent promoter (P nifA1 ) located upstream of orf71. This promoter contains canonical NifA upstream activating sequences located 91 bp from the transcription initiation site. The transcript initiated in P nifA1 spans 5.1 kb and includes nifA and nifB genes. NifA from Klebsiella pneumoniae was able to activate transcription from P nifA1 in a heterologous Escherichia coli system. In R. leguminosarum, the P nifA1 promoter is essential for effective nitrogen fixation in symbiosis with peas. In its absence, partially efficient nitrogen-fixing nodules were produced, and the corresponding bacteroids exhibited only low levels of nifA gene expression. The basal level of nifA expression resulted from a promoter activity originating upstream of the fixX-nifA intergenic region and probably from an incomplete duplication of P nifA1 located immediately upstream of fixA.