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1.
Phys Rev Lett ; 132(22): 222303, 2024 May 31.
Artículo en Inglés | MEDLINE | ID: mdl-38877919

RESUMEN

K^{+}K^{-} pairs may be produced in photonuclear collisions, either from the decays of photoproduced ϕ(1020) mesons or directly as nonresonant K^{+}K^{-} pairs. Measurements of K^{+}K^{-} photoproduction probe the couplings between the ϕ(1020) and charged kaons with photons and nuclear targets. The kaon-proton scattering occurs at energies far above those available elsewhere. We present the first measurement of coherent photoproduction of K^{+}K^{-} pairs on lead ions in ultraperipheral collisions using the ALICE detector, including the first investigation of direct K^{+}K^{-} production. There is significant K^{+}K^{-} production at low transverse momentum, consistent with coherent photoproduction on lead targets. In the mass range 1.1

2.
Phys Rev Lett ; 132(17): 172302, 2024 Apr 26.
Artículo en Inglés | MEDLINE | ID: mdl-38728735

RESUMEN

This Letter presents the measurement of near-side associated per-trigger yields, denoted ridge yields, from the analysis of angular correlations of charged hadrons in proton-proton collisions at sqrt[s]=13 TeV. Long-range ridge yields are extracted for pairs of charged particles with a pseudorapidity difference of 1.4<|Δη|<1.8 and a transverse momentum of 1

3.
Mol Biol (Mosk) ; 52(5): 898-904, 2018.
Artículo en Ruso | MEDLINE | ID: mdl-30363063

RESUMEN

The importance of root nodule bacteria in biotechnology is determined by their distinctive feature: symbiotic nitrogen fixation resulting in the production of organic nitrogen-containing compounds. While interacting with host legume plants, the cells of these bacteria undergo global changes at all levels of expression of genetic information leading to the formation in root nodules of so-called bacteroids functioning as nitrogen fixation factories. The molecular mechanisms underlying plant-microbial symbiosis are actively investigated, and one of the most interesting and poorly studied aspects of this problem is the species-specificity of interaction between root nodule bacteria and host plants. In this work we have performed the proteomic analysis of the Sinorhizobium meliloti bacteroids isolated from two legume species: alfalfa (Medicago sativa L.) and yellow sweet clover (Melilotus officinalis L.). It has been shown that the S. meliloti bacteroids produce a lot of proteins (many of them associated with symbiosis) in a host-specific manner, i.e., only in certain host plant species. It has been demonstrated for the first time that the levels of expression in bacteroids of the genes encoding the ExoZ and MscL proteins responsible for the synthesis of surface lipopolysaccha-rides and formation of a large conductance mechanosensitive channel, respectively, depend on a host plant species that confirms the results of proteomic analysis. Overall, our data show that the regulation of bacteroid development by the host plant has species-specific features.


Asunto(s)
Proteínas Bacterianas/metabolismo , Medicago sativa/microbiología , Proteoma , Sinorhizobium meliloti/metabolismo , Simbiosis , Fijación del Nitrógeno , Nódulos de las Raíces de las Plantas/microbiología
4.
Genetika ; 52(10): 1126-33, 2016 Oct.
Artículo en Ruso | MEDLINE | ID: mdl-29369582

RESUMEN

Genomes of 184 Sinorhizobium meliloti native isolates were studied to test the occurence of islands Sme21T, Sme19T, and Sme80S previously described in the model strain Rm1021. This analysis was conducted using PCR methodology involving specific primers. It was demonstrated that, in the examined geographically distinct populations of S. meliloti from the Northern Caucasus (NCG) and the Aral Sea region (PAG), the strains containing genomic islands were observed with similar frequency (0.55 and 0.57, respectively). Island Sme80S, denoted as an island of "environmental adaptivity," was identified predominantly (frequency of 0.38) in genomes of strains which exhibited a lower level of salt tolerance and was isolated in PAG, a modern center of introgressive hybridization of alfalfa subjected to salinity. Island Sme21T designated as "ancestral" was observed in genomes of strains isolated in NCG, the primary center of host-plant biodiversity, 10-fold more often than in strains from PAG. An island Sme19T, which predominantly carries genes encoding transposases, was observed in genomes of strains in both populations with average frequency of 0.10. The analysis of linkage disequilibrium (LD) based on the assessment of probability for detection of different islands combinations in genomes revealed an independent inheritance of islands in salt-sensitive strains of various geographic origin. In contrast, the absence of this trend was noted in the majority of the examined combinations of salt-tolerant strains. It was concluded that the structure of chromosome in PAG strains which predominantly possessed a salt-sensitive phenotype was subjected to active recombinant processes, which could predetermine the intensity of microevolutionary processes in bacterial populations and facilitate an adaptation of bacteria in adverse environmental effect.


Asunto(s)
Genoma Bacteriano , Islas Genómicas , Desequilibrio de Ligamiento , Sinorhizobium meliloti/genética , Sinorhizobium meliloti/aislamiento & purificación
5.
Genetika ; 51(10): 1108-16, 2015 Oct.
Artículo en Ruso | MEDLINE | ID: mdl-27169225

RESUMEN

Using high throughput sequencing of the nodA gene, we studied the population dynamics of Rhizobium leguminosarum (bv. viciae, bv. trifolii) in rhizospheric and nodular subpopulations associated with the leguminous plants representing different cross-inoculation groups (Vicia sativa, Lathyrus pratensis of the vetch/vetchling/pea group and Trifolium hybridum of the clover group). The "rhizosphere-nodules" transitions result in either an increase or decrease in the frequencies of 10 of the 23 operational taxonomic units (OTUs) (which were identified with 95% similarity) depending on the symbiotic specificity and phylogenetic positions of OTUs. Statistical and bioinformatical analysis of the population structures suggest that the type of natural selection responsible for these changes may be diversifying at the whole-population level and frequency-dependent at the OTU-specific level, ensuring the divergent evolution of rhizobia interacting with different host species.


Asunto(s)
Lathyrus/microbiología , Rhizobium leguminosarum/fisiología , Nódulos de las Raíces de las Plantas/microbiología , Selección Genética/fisiología , Simbiosis/fisiología , Trifolium/microbiología , Vicia sativa/microbiología
6.
Genetika ; 51(9): 973-90, 2015 Sep.
Artículo en Ruso | MEDLINE | ID: mdl-26606794

RESUMEN

In the present work, the potential for the enhancement of the adaptive capacity of microbe-plant systems (MPSs) through the integration of the symbiosis partners' genomes is considered on the example of different types of symbiotic relationships. The accumulated data on the genetic control of interactions for both the plant and microbe, which are discussed in the paper with respect to signaling genes, suggest that it is the complementarity of genetic determinants that underlies the successful formation of MPSs. A eukaryotic genome with limited information content, which is stable throughout a generation, is complemented by a virtually unlimited prokaryotic metagenome. The microsymbiont's ability to adapt to different living conditions is based on the restructuring of the accessory genome by different mechanisms, which are likely to be activated under the influence of plants, although the details of such a regulation remain unknown. Features of the genetic control of the interaction, particularly its universal character for different symbionts, allow us to formulate a principle of genome-complementarity with respect to interacting organisms and consider it an important factor, an adaptation that enhances the abilities of M PSs for their sustainable development in natural ecosystems and for high plant productivity in agrocenoses.


Asunto(s)
Adaptación Fisiológica/genética , Genes de Plantas/fisiología , Metagenoma/fisiología , Plantas/genética , Simbiosis/genética
7.
Mikrobiol Z ; 76(2): 24-8, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-25000726

RESUMEN

By using the method which has been developed for isolation and studying of microorganism strains, associative to particular plant species, the strain Pseudomonas fluorescens P10 has been isolated and its features of colonization of cabbage plant organs has been studied. In this study, different colonizing abilities of the strain are shown depending on the site of its isolation during germination and development of plants from inoculated seeds Brassica capitata var. alba Lizg. The ability of the strain to exist in epiphytic and endophytic forms and interaction with cabbage plants has been determined. It has been shown that this method can be used for strain activation during passage through plants.


Asunto(s)
Brassica/microbiología , Hojas de la Planta/microbiología , Raíces de Plantas/microbiología , Pseudomonas fluorescens/crecimiento & desarrollo , Recuento de Colonia Microbiana , Germinación , Pseudomonas fluorescens/aislamiento & purificación
8.
Prikl Biokhim Mikrobiol ; 49(3): 229-35, 2013.
Artículo en Ruso | MEDLINE | ID: mdl-23882940

RESUMEN

The review summarizes the results of studies on the comigration of tubercular bacteria and bean plants to new habitats, which is often accompanied by a decrease in the symbiosis efficiency due to a loss of the diversity of genes responsible for the interaction. This migration may lead to a rise in new symbionts as a result of gene transfers from initial symbionts to local bacteria. It was demonstrated that typically new symbionts lack an ability for N2 fixation but are highly competitive, blocking the inoculation of bean cultures by industrial strains. The design of coadapted systems of recognition and signal interaction of partners is a perspective approach to ensure competitive advantages of efficient rhizobia strains introduced into agrocenoses, together with host plants, over inactive local strains.


Asunto(s)
Fabaceae/genética , Rhizobium/genética , Nódulos de las Raíces de las Plantas/genética , Simbiosis/genética , Ecosistema , Fijación del Nitrógeno/genética , Fenómenos Fisiológicos de las Plantas , Raíces de Plantas , Nódulos de las Raíces de las Plantas/microbiología , Nódulos de las Raíces de las Plantas/fisiología , Especificidad de la Especie
9.
Heliyon ; 9(6): e17208, 2023 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-37360114

RESUMEN

Burial mounds represent a challenge for microbiologists. Could ancient buried soils preserve microbiomes as they do archaeological artifacts? To investigate this question, we studied the soil microbiome under a burial mound dating from 2500 years ago in Western Kazakhstan. Two soil profile cuts were established: one under the burial mound and another adjacent to the mound surface steppe soil. Both soils represented the same dark chestnut soil type and had the same horizontal stratification (A, B, C horizons) with slight alterations. DNA samples isolated from all horizons were studied with molecular techniques including qPCR and high throughput sequencing of amplicon libraries of the 16S rRNA gene fragment. The taxonomic structure of the microbiome of the buried horizons demonstrated a deep divergence from ones of the surface, comparable to the variation between different soil types (representatives of the soil types were included in the survey). The cause of this divergence could be attributed to diagenetic processes characterized by the reduction of organic matter content and changes in its structure. Corresponding trends in the microbiome structure are obvious from the beta-diversity pattern: the A and B horizons of the buried soils form one cluster with the C horizons of both buried and surface soil. This trend could generally be designated as 'mineralization'. Statistically significant changes between the buried and surface soils microbiomes were detected in the number of phylogenetic clusters, the biology of which is in the line of diagenesis. The trend of 'mineralization' was also supported by PICRUSt2 functional prediction, demonstrating a higher occurrence of the processes of degradation in the buried microbiome. Our results show a profound shift in the buried microbiome relatively the "surface" microbiome, indicating the deep difference between the original and buried microbiomes.

10.
Mol Ecol ; 20(22): 4808-21, 2011 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-21980996

RESUMEN

Legume plants can obtain combined nitrogen for their growth in an efficient way through symbiosis with specific bacteria. The symbiosis between Rhizobium galegae and its host plant Galega is an interesting case where the plant species G. orientalis and G. officinalis form effective, nitrogen-fixing, symbioses only with the appropriate rhizobial counterpart, R. galegae bv. orientalis and R. galegae bv. officinalis, respectively. The symbiotic properties of nitrogen-fixing rhizobia are well studied, but more information is needed on the properties of the host plants. The Caucasus region in Eurasia has been identified as the gene centre (centre of origin) of G. orientalis, although both G. orientalis and G. officinalis can be found in this region. In this study, the diversity of these two Galega species in Caucasus was investigated to test the hypothesis that in this region G. orientalis is more diverse than G. officinalis. The amplified fragment length polymorphism fingerprinting performed here showed that the populations of G. orientalis and R. galegae bv. orientalis are more diverse than those of G. officinalis and R. galegae bv. officinalis, respectively. These results support the centre of origin status of Caucasus for G. orientalis at a genetic level. Analysis of the symbiosis-related plant genes NORK and Nfr5 reveals remarkable diversity within the Nfr5 sequence, although no evidence of adaptive evolution could be found.


Asunto(s)
Galega/genética , Variación Genética , Genoma de Planta , Filogenia , Simbiosis/genética , Secuencia de Aminoácidos , Análisis del Polimorfismo de Longitud de Fragmentos Amplificados , ADN de Plantas/genética , Galega/microbiología , Datos de Secuencia Molecular , Rhizobium/fisiología , Federación de Rusia , Análisis de Secuencia de ADN
11.
Bull Exp Biol Med ; 148(5): 746-9, 2009 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-20396783

RESUMEN

Intensive terahertz irradiation at the nitric oxide emission and absorption spectrum frequencies (150.176-150.664 GHz) applied for 60 min to male albino rats subjected to acute immobilization stress enhanced platelet aggregation and induced signs of depression.


Asunto(s)
Conducta Animal/efectos de la radiación , Agregación Plaquetaria/efectos de la radiación , Radiación Terahertz , Animales , Humanos , Masculino , Ratas , Restricción Física , Estrés Fisiológico/fisiología , Factores de Tiempo
12.
Genetika ; 44(1): 12-28, 2008 Jan.
Artículo en Ruso | MEDLINE | ID: mdl-18409383

RESUMEN

Using the examples of diverse interactions among prokaryotes and eukaryotes, the relationships between molecular and population mechanisms of evolution of symbiotic bacteria are addressed. Their circulation in host-environment systems activates microevolutionary factors that direct combinative or reductive genome evolution in facultative, ecologically obligatory, and genetically obligatory symbioses. Due to intense systemic intra-genome rearrangements and horizontal gene transfer, two types of gene systems evolve in these bacteria: (1) controlling the pathogenesis-like processes of host recognition and penetration and (2) responsible for mutualistic interactions that are related to nitrogen fixation and its transfer to the host. The evolution of gene systems of type 1 is directed by individual (Darwinian, frequency-dependent) selection, which is responsible for gene-for-gene interactions between the partners. In the evolution of the type 2 systems, group (interdeme, kin) selection plays the key role, being responsible for the development of bacterial traits beneficial for the host. Using the legume--rhizobia symbiosis as an example, it is shown that evolution of mutualism can be described in terms of biological altruism, whose regularities are common for intraspecific and interspecific relationships. Macroevolutionary rearrangements of bacterial genomes result from the structural changes in their populations, wherein various selection modes are combined with stochastic processes (genetic drift, population waves) induced in the symbiotic systems.


Asunto(s)
Bacterias/genética , Fenómenos Fisiológicos Bacterianos , Evolución Molecular , Fenómenos Fisiológicos de las Plantas , Plantas/genética , Simbiosis/fisiología , Bacterias/metabolismo , Flujo Genético , Genoma Bacteriano/fisiología , Genoma de Planta/fisiología , Plantas/metabolismo , Selección Genética
13.
Usp Fiziol Nauk ; 39(4): 83-91, 2008.
Artículo en Ruso | MEDLINE | ID: mdl-19241806

RESUMEN

Nitric oxide plays a dominant role in regulation of different cells, tissues, organs and system in the body including cardiovascular system. Take into consideration a major role of microcirculatory disorders in pathogenesis of various illnesses in this review take up the role of nitric oxide in microcirculatory regulation, especially of it intravascular component, witch functioning depends from the functions of microcirculatory unit of hemostasis system.


Asunto(s)
Hemostasis , Microcirculación , Óxido Nítrico/fisiología , Animales , Plaquetas/metabolismo , Vasos Sanguíneos/metabolismo , Enfermedades Cardiovasculares/sangre , Endotelio Vascular , Deformación Eritrocítica , Eritrocitos , Humanos , Óxido Nítrico/metabolismo
14.
Front Plant Sci ; 9: 344, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29706972

RESUMEN

Sandwich-like docking configurations of the heterodimeric complex of NFR5 and K1 Vicia sativa receptor-like kinases together with the putative ligand, Nod factor (NF) of Rhizobium leguminosarum bv. viciae, were modeled and two of the most probable configurations were assessed through the analysis of the mutual polymorphisms and conservatism. We carried out this analysis based on the hypothesis that in a contact zone of two docked components (proteins or ligands) the population polymorphism or conservatism is mutual, i.e., the variation in one component has a reflected variation in the other component. The population material of 30 wild-growing V. sativa (leaf pieces) was collected from a large field (uncultivated for the past 25-years) and pooled; form this pool, 100 randomly selected cloned fragments of NFR5 gene and 100 of K1 gene were sequenced by the Sanger method. Congruence between population trees of NFR5 and K1 haplotypes allowed us to select two respective haplotypes, build their 3D structures, and perform protein-protein docking. In a separate simulation, the protein-ligand docking between NFR5 and NF was carried out. We merged the results of the two docking experiments and extracted NFR5-NF-K1 complexes, in which NF was located within the cavity between two receptors. Molecular dynamics simulations indicated two out of six complexes as stable. Regions of mutual polymorphism in the contact zone of one complex overlapped with known NF structural variations produced by R. leguminosarum bv. viciae. A total of 74% of the contact zone of another complex contained mutually polymorphic and conservative areas. Common traits of the obtained two stable structures allowed us to hypothesize the functional role of three-domain structure of plant LysM-RLKs in their heteromers.

15.
Radiats Biol Radioecol ; 47(4): 476-80, 2007.
Artículo en Ruso | MEDLINE | ID: mdl-17953435

RESUMEN

The effects of external acute irradiation at dose 1.0 Gy on biologic, haematologic and metabolic changes in blood of alloxan-induced diabetic rats were studied. It was found that the deterioration of diabetic animals occurs in different terms after irradiation exposure, resulting in considerable body weight decrease, well-marked hyperglycemia, abrupt falling of leukocytic system parameters, intensification energetic processes of extant lymphocytes, imbalance of lipid metabolism and thyroid state, as well as significant inhibition of 5'-deiodinase activity in liver tissue.


Asunto(s)
Diabetes Mellitus Experimental/complicaciones , Rayos gamma/efectos adversos , Traumatismos Experimentales por Radiación/metabolismo , Aloxano/toxicidad , Animales , Peso Corporal/efectos de la radiación , Yoduro Peroxidasa/antagonistas & inhibidores , Yoduro Peroxidasa/efectos de la radiación , Recuento de Leucocitos , Leucocitos/efectos de la radiación , Metabolismo de los Lípidos/efectos de la radiación , Lípidos/sangre , Masculino , Traumatismos Experimentales por Radiación/sangre , Traumatismos Experimentales por Radiación/complicaciones , Ratas , Ratas Endogámicas , Glándula Tiroides/efectos de la radiación , Tiroxina/sangre , Triyodotironina/sangre
16.
Mikrobiologiia ; 85(2): 115-25, 2016.
Artículo en Ruso | MEDLINE | ID: mdl-27476200

RESUMEN

The processes of speciation and macroevolution of root nodule bacteria (rhizobia), based on deep rearrangements of their genomes and occurring in the N2-fixing symbiotic system, are reconstructed. At the first stage of rhizobial evolution, transformation of free-living diazotrophs (related to Rhodopseudomonas) to symbiotic N2-fixers (Bradyrhizobium) occurred due to the acquisition of the fix gene system, which is responsible for providing nitrogenase with electrons and reducing equivalents, as well as for oxygen-dependent regulation of nitrogenase synthesis in planta, and then of the nod genes responsible for the synthesis of the lipo- chito-oligosaccharide Nod factors, which induce root nodule development. The subsequent rearrangements of bacterial genomes included: (1) increased volume of hereditary information supported by species, genera (pan-genome), and individual strains; (2) transition from the unitary genome to a multicomponent one; and (3) enhanced levels of bacterial genetic plasticity and horizontal gene transfer, resulting in formation of new genera, of which Mesorhizobium, Rhizobium, and Sinorhizobium are the largest, and of over 100 species. Rhizobial evolution caused by development and diversification of the Nod factor synthesizing systems may result in both increased host specificity range (transition of Bradyrhizobium from autotrophic to symbiotrophic carbon metabolism in interaction with a broad spectrum of legumes) and to its contraction (transition of Rhizobium and Sinorhizobium to "altruistic" interaction with legumes of the galegoid clade). Reconstruction of the evolutionary pathway from symbiotic N2-fixers to their free-living ancestors makes it possible to initiate the studies based on up-to-date genome screening technologies and aimed at the issues of genetic integration of organisms into supracpecies complexes, ratios of the macro- and microevolutionary mechanisms, and developmetn of cooperative adaptations based on altruistic relationship between the symbiotic partners.


Asunto(s)
Bacterias , Evolución Molecular , Genoma Bacteriano/fisiología , Nódulos de las Raíces de las Plantas/microbiología , Simbiosis/fisiología , Bacterias/genética , Bacterias/metabolismo
17.
Mikrobiologiia ; 85(2): 199-210, 2016.
Artículo en Ruso | MEDLINE | ID: mdl-27476208

RESUMEN

Effects of long-term application ofvarious fertilizers and crops on soil microbiomes an a long-term field experiment were investigated using the library of the 16S rRNA gene sequences obtained by high-throughput sequencing of the total DNA. The communities exhibited high diversity, with 655 microbial genera belonging to 34 phyla detected (31 bacterial and 3 archaeal ones). For analysis of the effect of the studied factors on community structure, a linear model was developed in order to simplify interpretation of the data of high-throughput sequencing and to obtain biologically important information. Liming was shown to modulate the effect of mineral fertilizers on the structure of microbial populations. The differences in the structure and alpha-diversity of microbial communities were shown to depend more on the crops and liming, rather than on the fertilizers applied. Interaction between the crop factor and liming expressed as an ambiguous effect of liming on the microbiome in the presence of different plants was reliably demonstrated. Thus, in the case of barley and clover, liming resulted in increased taxonomic diversity of the community, while in the case of potato and flax it had an opposite effect.


Asunto(s)
Bacterias/genética , Producción de Cultivos , ADN Bacteriano/genética , Fertilizantes , ARN Ribosómico 16S/genética , Microbiología del Suelo , Bacterias/clasificación
18.
Genetika ; 37(5): 610-6, 2001 May.
Artículo en Ruso | MEDLINE | ID: mdl-11436551

RESUMEN

Fifty-six natural strains of alfalfa nodule bacteria were isolated from samples of the soil under wild legume and alfalfa in two different field sites of Irkutsk oblast. Based on the results of analysis of plasmid profile, 11 different types of strains were detected, and 43 types were identified based on the results of hybridization with the insertion sequence element ISRm2011-2. Significant differences were found in the plasmid profile and IS fingerprints between strains isolated from the soil under alfalfa and the soil under legume. In contrast, strains growing at some distance from each other differed only in the IS fingerprints. From a comparison of results obtained in the assessment of plasmid profile and in analysis of IS fingerprints with results of RFLP analysis in strains, the conclusion about the transference of cryptic plasmids between strains and genetic rearrangements in strains of this population was drawn.


Asunto(s)
Dermatoglifia del ADN , Variación Genética , Plásmidos , Sinorhizobium meliloti/genética , Medicago sativa/microbiología , Hibridación de Ácido Nucleico , Polimorfismo de Longitud del Fragmento de Restricción
19.
Genetika ; 40(4): 454-61, 2004 Apr.
Artículo en Ruso | MEDLINE | ID: mdl-15174277

RESUMEN

Instability of cryptic plasmids in Sinorhizobium meliloti laboratory strains SKhM1-188, DM7-R, and P108 as well as in their clones isolated from nodules of alfalfa grown during a long-term microvegetation experiment (120 days) was studied. The isolated clones of strains SKhM1-188 and DM7-R manifested stable inheritance of plasmids, whereas 12.7-14.0% of clones with changed plasmid profile were detected in a population of clones from strain P108. These segregants were designated as P108c. Segregants P108c exhibited significantly decreased symbiotic effectiveness, nitrogenase activity, and the competitiveness with respect to alfalfa, compared to the original strain P108. It was established that a 80-kb deletion occurred in a larger of two cryptic plasmids (240 and 230 kb) of segregants P108c. It was concluded that genetic rearrangements are possible in rhizobial clones that did not undergo structural transformation and retained viability in the nodule during the natural vegetation period of alfalfa.


Asunto(s)
Medicago sativa/microbiología , Plásmidos , Sinorhizobium meliloti/fisiología , Simbiosis/genética , Sinorhizobium meliloti/genética
20.
Mikrobiologiia ; 83(4): 500-8, 2014.
Artículo en Ruso | MEDLINE | ID: mdl-25844461

RESUMEN

High-throughput sequencing of the amplicon gene library revealed variations in the population structure of clover rhizobia (Rhizobium leguminosarum bv. trifolii) upon transition from soil into the root nodules of the host plant (Trifolium-hybridum). Analysis of rhizobial-diversity using the nodA gene revealed 3258 and 1449 nucleotide sequences (allelic-variants) for the soil and root nodule population, respectively. They were combined into 29 operational taxonomic units (OTU) according to the 97% identity level; 24 OTU were. foundin the soil population, 12 were present in the root nodulepopulation, and 7 were common. The predominant OTE13 (77.4 and 91.5% of the soil and root nodule populations, respectively) contained 155 and -200 variants of the soil and root nodule populations, respectively, with the nucleotide diversity increasing significantly upon the "soil-->root" transition. The "moving window" approach was used to reveal the sites of the nodA gene in which polymorphism, including that associated with increased frequency of non-synonymous substitution frequency, increased sharply upon transition from soil into root nodiles. PCR analysis of the IGS genotypes of individual strains revealed insignificant changes in rhizobial diversity upon transition from soil into root nodules. These results indicate that acceleration of rhizobial evolutioin in the course of symbiosis may be associated with development of highly polymorphic virulent:subpopulations subjected to directional selection in the "plant-soil" system.


Asunto(s)
Medicago/microbiología , Micorrizas/fisiología , Rhizobium/clasificación , Rhizobium/fisiología , Nódulos de las Raíces de las Plantas/microbiología , Microbiología del Suelo
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