Characterization of Rhizobium from root nodules of leguminous trees growing in alkaline soils

1997 ◽  
Vol 43 (9) ◽  
pp. 891-894 ◽  
Author(s):  
S. Surange ◽  
A. G. Wollum II ◽  
N. Kumar ◽  
C. Shekhar Nautiyal
Keyword(s):  
High Temperature ◽  
Root Nodules ◽  
Carbon Sources ◽  
Alkaline Soils ◽  
Variable Response ◽  
Leguminous Trees ◽  
Acacia Farnesiana ◽  
Rhizobium Strains ◽  
Albizia Lebbek

High temperature, pH, and salt stresses in tropical alkaline soils limit nodulation and dinitrogen fixation by strains of Rhizobium from the root nodules of nitrogen fixing trees (NFTs). This study was conducted to determine the variability among Rhizobium strains isolated from different NFTs in growth response to high temperature, pH, and salt concentrations. Variable response to increases in temperature, pH, and salt concentrations was observed. Rhizobium strain isolated from Albizia lebbek survived at 50 °C, while Rhizobium strains isolated from Sesbania formosa, Acacia farnesiana, and Dalbergia sissoo were well adapted to grow on pH 12.0. All the Rhizobium strains tolerated salt concentrations up to 5.0%. Strains were further characterized with respect to utilization of 27 carbon sources and for their effectiveness in substrate utilization at pH 7.0 and 9.0. Generally higher rates of O2 consumption were observed at pH 7.0 compared with pH 9.0.Key words: Rhizobium, leguminous trees, root nodules, stress tolerance.

scholarly journals Characterization of the growth of Rhizobium trifolii and Sinorhizobium meliloti in different culture media

2013 ◽  
Vol 70 (1) ◽  
pp. 80-86
Author(s):  
Monica NISTE ◽  
Roxana VIDICAN ◽  
Ioan ROTAR ◽  
Rodica POP
Keyword(s):  
Sinorhizobium Meliloti ◽  
Trifolium Pratense ◽  
Culture Media ◽  
Root Nodules ◽  
Plant Host ◽  
Symbiotic Interactions ◽  
Rhizobium Strains ◽  
Yeast Extract Mannitol ◽  
Different Strains

Legumes have the ability to form symbiotic interactions with soil bacteria, called rhizobia. Bacteria of the genus Rhizobium are able to convert atmospheric nitrogen into ammonia when compounds are exchanged between the bacteroid and its plant host. The present study describes the characterization of Rhizobium strains isolated from root nodules of Trifolium pratense and Medicago sativa grown in a greenhouse. The main objective of the experiment was to identify which medium is more suitable for the development of different strains of rhizobia. The Rhizobium strains are rod shaped, Gram negative and mucus producing. The rhizobia were identified and isolated using different media yeast extract mannitol agar (YEMA) containing Congo red, and a medium including boron (B), an essential micronutrient. The Petri plates were incubated at 28ºC and inspected three days after the inoculation. The colony morphology was analysed based on type, appearance, transparency, colour and the effectiveness of boron on Rhizobium growth.

scholarly journals Fabrication and Characterization of Quinary High Entropy-Ultra-High Temperature Diborides

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 108-120
Author(s):  
Simone Barbarossa ◽  
Roberto Orrù ◽  
Valeria Cannillo ◽  
Antonio Iacomini ◽  
Sebastiano Garroni ◽  
...  
Keyword(s):  
High Temperature ◽  
Single Phase ◽  
Nominal Composition ◽  
High Entropy ◽  
Chemical Complexity ◽  
Alternative Processing ◽  
Plasma Sintering ◽  
High Temperature Synthesis ◽  
Spark Plasma

Due to their inherent chemical complexity and their refractory nature, the obtainment of highly dense and single-phase high entropy (HE) diborides represents a very hard target to achieve. In this framework, homogeneous (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2, (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2, and (Hf0.2Zr0.2Nb0.2Mo0.2Ti0.2)B2 ceramics with high relative densities (97.4, 96.5, and 98.2%, respectively) were successfully produced by spark plasma sintering (SPS) using powders prepared by self-propagating high-temperature synthesis (SHS). Although the latter technique did not lead to the complete conversion of initial precursors into the prescribed HE phases, such a goal was fully reached after SPS (1950 °C/20 min/20 MPa). The three HE products showed similar and, in some cases, even better mechanical properties compared to ceramics with the same nominal composition attained using alternative processing methods. Superior Vickers hardness and elastic modulus values were found for the (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2 and the (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2 systems, i.e., 28.1 GPa/538.5 GPa and 28.08 GPa/498.1 GPa, respectively, in spite of the correspondingly higher residual porosities (1.2 and 2.2 vol.%, respectively). In contrast, the third ceramic, not containing tantalum, displayed lower values of these two properties (25.1 GPa/404.5 GPa). However, the corresponding fracture toughness (8.84 MPa m1/2) was relatively higher. This fact can be likely ascribed to the smaller residual porosity (0.3 vol.%) of the sintered material.

scholarly journals Multianvil High-Pressure/High-Temperature Synthesis and Characterization of multiferroic HP-Co3TeO6

2021 ◽  
Author(s):  
Gunter Heymann ◽  
Elisabeth Selb ◽  
Toni Buttlar ◽  
Oliver Janka ◽  
Martina Tribus ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Type Structure ◽  
Synthesis And Characterization ◽  
Temperature Synthesis ◽  
Space Group ◽  
Crystal System ◽  
High Temperature Synthesis ◽  
High Pressure High Temperature

By high-pressure/high-temperature multianvil synthesis a new high-pressure (HP) phase of Co3TeO6 was obtained. The compound crystallizes in the acentric trigonal crystal system of the Ni3TeO6-type structure with space group R3...

scholarly journals Genetic Analysis of Mutations Affecting pckA Regulation in Rhizobium (Sinorhizobium) meliloti

Genetics ◽  
1997 ◽  
Vol 147 (4) ◽  
pp. 1521-1531 ◽  
Author(s):  
Magne Østerås ◽  
Shelley A P O'Brien ◽  
Turlough M Finan
Keyword(s):  
Sinorhizobium Meliloti ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Root Nodules ◽  
Genetic Regulation ◽  
Carbon Sources ◽  
Dicarboxylic Acids ◽  
Phenotypic Analysis ◽  
Gene Encoding ◽  
Type Locus ◽  
Rapid Induction

Abstract The enzyme phosphoenolpyruvate carboxykinase (Pck) catalyzes the first step in the gluconeogenic pathway in most organisms. We are examining the genetic regulation of the gene encoding Pck, pckA, in Rhizobium (now Sinorhizobium) meliloti. This bacterium forms N2-fixing root nodules on alfalfa, and the major energy sources supplied to the bacteria within these nodules are C4-dicarboxylic acids such as malate and succinate. R. meliloti cells growing in glucose minimal medium show very low pckA expression whereas addition of succinate to this medium results in a rapid induction of pckA transcription. We identified spontaneous mutations (rpk) that alter the regulation of pckA expression such that pckA is expressed in media containing the non-inducing carbon sources lactose and glucose. Genetic and phenotypic analysis allowed us to differentiate at least four rpk mutant classes that map to different locations on the R. meliloti chromosome. The wild-type locus corresponding to one of these rpk loci was cloned by complementation, and two Tn5 insertions within the insert DNA that no longer complemented the rpk mutation were identified. The nucleotide sequence of this region revealed that both Tn5 insertions lay within a gene encoding a protein homologous to the Ga1R/LacI family of transcriptional regulators that are involved in metabolism.

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