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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 32 (2000), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Strains of Rhizobium leguminosarum bv. viciae, isolated from the legume species Lathyrus japonicus and Lathyrus pratensis in northern Quebec (Canada), showed different capacities for growing at low temperature. In the present study, we investigated some mechanisms related to cold adaptation. Two cold-adapted strains (psychrotrophs) were compared to a poorly adapted strain and to a cold-sensitive strain (reference strain) for freezing survival, protein induction and fatty acid composition under low temperature. Following cold shocks (25°C to 10, 5 and 0°C), a common 6.1-kDa CSP (cold shock protein) was induced in all strains, but the total number of CSPs synthesized at 0°C was higher in cold-adapted strains than in the cold-sensitive strain. The synthesis of CAPs (cold acclimation proteins) was observed under continuous growth at 5°C in all three strains capable of growth at this temperature. Levels of survival after 24 h at −80°C where higher in cold- (79%) and poorly adapted (64%) strains than in the cold-sensitive strain (33%), but a 2-h acclimation period at 5°C before freezing doubled the survival of the cold-sensitive strain. Low temperature conditions affected similarly the fatty acid composition of all strains, regardless of their cold adaptation level. The proportion of unsaturated fatty acids increased significantly with the lowering of growth temperature from 25 to 5°C, but showed a tendency to decrease after a cold shock from 25 to 5°C. A specific unsaturated fatty acid, cis-12 octadecanoic acid, was produced during growth at 5°C. The unsaturated cis-vaccenic acid was the principal component under all conditions. The cold adaptation trait was weakly reflected in symbiosis with the agronomic legume, Lathyrus sativus, with which one cold-adapted strain showed a slightly higher nitrogenase activity and shoot dry matter yield than a commercial strain under a sub-optimal temperature regime.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 45 (1987), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The temperate forage legume sainfoin (Onobrychis viciifolia) is readly nodulated by rhizobia isolated from arctic legumes (Astragalus and Oxytropis species). We have investigated the effects of low temperatures on nitrogenase activity in sainfoin nodulated by arctic and temperate (homologous) rhizobia. At low temperatures, nitrogenase activity of arctic rhizobia measured either with detached nodules or with whole plants, was higher than that of temperate rhizobia. At 5°C and 10°C, nitrogenase activity values of arctic rhizobia represented 12% and 33% of those measured at 20°C, while lower values of 3.7% and 22.4% were observed with temperate rhizobia. This cold adaptation was also reflected on bacterial growth where, at 5°C and 10°C, arctic rhizobia showed a shorter doubling time and synthesized more protein than temperate rhizobia.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 146 (1986), S. 12-18 
    ISSN: 1432-072X
    Keywords: Arctic rhizobia ; Arctic legumes ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Forty-eight strains of Rhizobium isolated from the root nodules of three species of legumes indigenous to the high tundra (Astragalus alpinus, Oxytropis maydelliana andOxytropis arctobia) are phenotypically heterogenous with respect to intrinsic antibiotic resistance, expression of nitrogenase activityex planta and plasmid content. All of the strains possess a 250–300 kb plasmid and are homologous to each other on the genomic DNA level but have little DNA homology with selected reference strains of well characterized species of rhizobia. The arctic rhizobia have an optimum growth temperature of 23°C and can grow slowly at 5°C. The DNA from four of the isolates, which were selected for detailed investigation, have sequences homologous tonif andnod genes fromRhizobium trifolii.
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  • 4
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Denitrification ; Nitrification ; Nitrate ; Organic C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field study was undertaken to determine the effects of different plant species on soil microbial biomass and N transformations in a well drained silty clay loam (Typic Dystrochrept) and a poorly drained clay loam (Typic Humaquept). The crop treatments were faba bean (Vicia faba L.), alfalfa (Medicago sativa L.), timothy (Phleum pratense L.), bromegrass (Bromus inermis L.), reed canarygrass (Phalaris arundinacea L.), and wheat (Triticum aestivum L.). Measurements of microbial biomass C, denitrification capacity, and nitrification capacity were performed periodically in the top 2–10 cm of soil. On most sampling dates, all three parameters were higher under perennial than under annual species. The nitrification capacity was positively affected by the level of N applied to each species (r=0.65** for the silty clay loam and 0.84*** for the clay loam) and not directly by the plant. The differences found in microbial biomass C were significantly correlated with the water-soluble organic C present under each plant species (r=0.74*** for the silty clay loam and 0.90*** for the clay loam), suggesting differences in C deposition in the soil among plant species. In the silty clay loam, the denitrification capacity was positively related to the amount of organic C found under each plant species, while in the clay loam, it was dependent on the amount of N applied to each species. There was less denitrification activity per unit biomass under legume species than under graminease, suggesting that, depending on their composition, root-derived materials may be used differently by soil microbes.
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  • 5
    ISSN: 1432-0789
    Keywords: Key words Microbial biomass ; Denitrification ; Nitrification ; Nitrate ; Organic C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field study was undertaken to determine the effects of different plant species on soil microbial biomass and N transformations in a well drained silty clay loam (Typic Dystrochrept) and a poorly drained clay loam (Typic Humaquept). The crop treatments were faba bean (Vicia faba L.), alfalfa (Medicago sativa L.), timothy (Phleum pratense L.), bromegrass (Bromus inermis L.), reed canarygrass (Phalaris arundinacea L.), and wheat (Triticum aestivum L.). Measurements of microbial biomass C, denitrification capacity, and nitrification capacity were performed periodically in the top 2–10 cm of soil. On most sampling dates, all three parameters were higher under perennial than under annual species. The nitrification capacity was positively affected by the level of N applied to each species (r=0.65** for the silty clay loam and 0.84*** for the clay loam) and not directly by the plant. The differences found in microbial biomass C were significantly correlated with the water-soluble organic C present under each plant species (r=0.74*** for the silty clay loam and 0.90*** for the clay loam), suggesting differences in C deposition in the soil among plant species. In the silty clay loam, the denitrification capacity was positively related to the amount of organic C found under each plant species, while in the clay loam, it was dependent on the amount of N applied to each species. There was less denitrification activity per unit biomass under legume species than under gramineae, suggesting that, depending on their composition, root-derived materials may be used differently by soil microbes.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 66 (1982), S. 45-50 
    ISSN: 1573-5036
    Keywords: Alfalfa ; Antibiotic disks ; Bacteria ; Plant ; Rhizobium meliloti ; Strain identification ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The antibiotic disk susceptibility test was used to measure the variation in the intrinsic resistance of 49 strains ofRhizobium meliloti to 9 antibiotics. Several strains had unique patterns of resistance. However, during cluster analysis, when a minimum Euclidean distance equal to 4 was used as a discriminating tool, the strains were grouped in 12 groups. The largest group contained 74% of the strains but 9 strains (2 very effective, 4 effective and 3 ineffective) showed very unique patterns of resistance and formed 9 distinct groups.R. meliloti strains in general showed high intrinsic resistance to the 9 antibiotics tested.
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  • 7
    ISSN: 1573-5036
    Keywords: arctic ; effectiveness ; N2-fixation ; Onobrychis ; Rhizobium ; symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Sainfoin (Onobrychis viciifolia), a temperate perennial forage legume, can be nodulated by rhizobia isolated from 3 arctic legume species:Astragalus alpinus, oxytropis maydelliana andOxytropis arctobia. Arctic rhizobia, which are adapted to growth at low temperatures, may be useful in improving symbiotic nitrogen fixation during cold phases of the growing season, if they are effective on a temperate legume. In this study, we report on the symbiotic effectiveness of arctic rhizobia on sainfoin, as appraised by the total shoot dry matter yield obtained from 2 harvests. Under N-free conditions, 5 arctic strains at the first harvest and 8 at the second harvest were as effective as temperate standard strains. In the presence of 30 mgl−1 NO3-N, 7 arctic strains gave significantly higher yields than temperate strains at the second harvest. These results indicate that effective arctic rhizobia have a potential for use as inoculants on sainfoin.
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  • 8
    ISSN: 1573-5036
    Keywords: Arctic ; Astragalus ; Legumes ; Numerical analysis ; Oxytropis ; Rhizobium ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Forty-eight strains of rhizobia were isolated from the root nodules ofAstragalus alpinus (21),Oxytropis maydelliana (19) andOxytropis arctobia (8), three species of arctic legumes found in the Melville Peninsula, Northwest Territories, Canada. On the basis of 74 characteristics (cultural, physiological, biochemical and host nodulation range) the 48 arctic rhizobia could be divided into 11 distinct groups by numerical analysis techniques. All 48 arctic rhizobia were able to nodulate the three arctic legume species and also sainfoin (Onobrychis viciifolia), however, milkvetch (Astragalus cicer) was only nodulated by 33 strains. In general, the arctic rhizobia showed properties found in both Rhizobium and Bradyrhizobium. The adaptation of the arctic strains to low temperature is indicated by their ability to grow in liquid culture at 5°C.
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  • 9
    Publication Date: 2004-01-01
    Print ISSN: 0361-5995
    Electronic ISSN: 1435-0661
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 10
    Publication Date: 1999-11-01
    Description: While some studies indicate no denitrification activity in early spring, others have demonstrated that denitrifiers from temperate region soils can adapt to low temperatures. The aim of the present paper was to study how seasonal changes in temperature affect denitrifying enzyme activity (DEA) in a cropped humic gleysol located in a cold temperate climate (Quebec). Soil was sampled monthly during a 16-mo period and DEA was measured at nine temperatures from 2 to 35°C. A seasonal effect of temperature on DEA was significant at all incubation temperatures and was more important in November and in May–June. The effect of temperature on DEA was better fitted with the square root model of Ratkowsky than with the Arrhenius equation. The regression coefficient b (Ratkowsky parameter) varied seasonally with a trend similar to that of DEA. These results show that the Ratkowsky model should be used instead of Arrhenius equation to describe the effect of cold temperature on denitrification. Key words: Denitrification, temperature, cold, Arrhenius equation, Ratkowsky model
    Print ISSN: 0008-4271
    Electronic ISSN: 1918-1841
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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