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  • Nitrogen fixation  (36)
  • Springer  (36)
  • Periodicals Archive Online (PAO)
  • 1985-1989  (36)
  • 1980-1984
  • 1975-1979
  • 1987  (36)
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Keywords
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  • Springer  (36)
  • Periodicals Archive Online (PAO)
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  • 1985-1989  (36)
  • 1980-1984
  • 1975-1979
Year
  • 1
    Electronic Resource
    Electronic Resource
    Cellular compartmentation of ureide biogenesis in root nodules of cowpea (Vigna unguiculata (L.) Walp.) (1987)
    Springer
    Planta 172 (1987), S. 162-175 
    Details
    ISSN: 1432-2048
    Keywords: Nitrogen fixation ; Peroxisome ; Root nodules ; Ureide biogenesis ; Uricase ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cowpea (Vigna unguiculata (L.) Walp.) nodules have been investigated by means of cytochemical and immunocytochemical procedures at the ultrastructural level in order to assess the role of the uninfected cells in ureide biogenesis. Uricase activity in the nodules was shown by cytochemical methods to be localized exclusively in the numberous large peroxisomes confined to the uninfected cells; the small peroxisomes in the infected cells did not stain for uricase. Uricase was also localized in the peroxisomes of uninfected cells by immunogold techniques employing polyclonal antibodies against nodule-specific uricase of soybean. There was no labeling above background of any structures in the infected cells. The results indicate that the uninfected cells are essential for ureide biogenesis in cowpea. Although tubular endoplasmic reticulum, the presumptive site of allantoinase, increases greatly in the uninfected cells during nodule development, it virtually disappears as the nodules mature. The inconsistency between the disappearance of the tubular endoplasmic reticulum from older nodules and the high allantoinase activity reported for older plants remains to be explained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394584
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of nitrogen fixation, soil nitrate, and defoliation on the growth, alkaloids, and nitrogen levels of Lupinus succulentus (Fabaceae) (1987)
    Springer
    Oecologia 74 (1987), S. 425-431 
    Details
    ISSN: 1432-1939
    Keywords: Lupinus succulentus ; Fabaceae ; Lupine ; Quinolizidine alkaloids ; Nitrogen fixation ; Defoliation ; Plant-herbivore interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We examined the effects of nitrogen nutrition and defoliation on the alkaloids, nitrogen levels, and growth of Lupinus succulentus by growing plants under five nitrogen/defoliation treatments: 1) fertilization with a high-nitrate nutrient solution, 2) fertilization with a low-nitrate solution, 3) inoculation with N-fixing bacteria but without available soil nitrogen, 4) high-nitrate solution plus periodic partial defoliation, and 5) low-nitrate plus defoliation. In the absence of defoliation, plants from both the N-fixing and high-N treatments had higher concentrations of alkaloids and nitrogen, and higher growth rates than the low-N plants. Periodic defoliation had little effect on the high-N plants, but defoliated N-fixing plants were severely stunted and had lower alkaloid and nitrogen levels. The experimental treatments also affected the relative concentrations of the alkaloids. Our results indicate that 1) alkaloid composition and concentration in L. succulentus are determined by both nitrogen availability and developmental state, 2) plants relying solely on N-fixation respond quite differently to defoliation than those with adequate soil nitrogen, and 3) the food value of the plant tissue can be affected by an interaction between the effects of defoliation and nitrogen status.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378940
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  • 3
    Electronic Resource
    Electronic Resource
    Localization of nitrogenase in vesicles of Frankia sp. Cc1.17 by immunogoldlabelling on ultrathin cryosections (1987)
    Springer
    Archives of microbiology 146 (1987), S. 327-331 
    Details
    ISSN: 1432-072X
    Keywords: Actinomycetes ; Nitrogen fixation ; Symbiosis ; Immunocytochemistry ; Ultracryotomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Immunogoldlabelling on ultrathin cryosections of Frankia sp. Cc1.17 showed specific labelling of nitrogenase in the spherical cells called vesicles. No label was found in the hyphae in any cells grown on a medium with combined nitrogen, nor in those to which no specific antiserum was added. Similar results were obtained with cultures grown under high (20%) and low (2%) oxygen tension in the gas phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00410930
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  • 4
    Electronic Resource
    Electronic Resource
    Comparative physiology of nitrogenase activity and vesicle development for Frankia strains CpI1, ACN1 ag , EAN1pec and EUN1f (1987)
    Springer
    Archives of microbiology 147 (1987), S. 383-388 
    Details
    ISSN: 1432-072X
    Keywords: Frankia ; Nitrogen fixation ; Vesicle development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between nitrogen fixation and development of a specialized cell structure, called the vesicle, was studied using four Frankia isolates. Nitrogenase activity was repressed in all four strains during growth with ammonia. Strain CpI1 formed no vesicles during NH4 growth. Strains ACN1 ag , EAN1pec and EUN1f produced low numbers of vesicles in the presence of ammonia. Following transfer to nitrogen-free media, a parallel increase in nitrogenase activity and vesicle numbers occurred with all four isolates. Appearance of nitrogenase activity was more rapid in those strains that possessed some vesicles at the time of shift to N2 as a nitrogen source. The ratio of vesicle numbers to level of nitrogenase activity varied widely among the four strains and in response to different growth conditions and culture age of the individual strains. Optimum conditions of temperature, carbon and energy source, nitrogen source and availability of iron and molybdenum were different for each of the four strains. Those conditions that significantly reduced nitrogenase activity were always associated with decreased numbers of vesicles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00406137
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  • 5
    Electronic Resource
    Electronic Resource
    New types of acetate-oxidizing, sulfate-reducing Desulfobacter species, D. hydrogenophilus sp. nov., D. latus sp. nov., and D. curvatus sp. nov. (1987)
    Springer
    Archives of microbiology 148 (1987), S. 286-291 
    Details
    ISSN: 1432-072X
    Keywords: Sulfate-reducing bacteria ; Desulfobacter species ; Acetate ; Hydrogen ; Autotrophic growth ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sulfate-reducing bacteria with oval to rod-shaped cells (strains AcRS1, AcRS2) and vibrio-shaped cells (strains AcRM3, AcRM4, AcRM5) differing by size were isolated from anaerobic marine sediment with acetate as the only electron donor. A vibrio-shaped type (strain AcKo) was also isolated from freshwater sediment. Two strains (AcRS1, AcRM3) used ethanol and pyruvate in addition to acetate, and one strain (AcRS1) grew autotrophically with H2, sulfate and CO2. Higher fatty acids or lactate were never utilized. All isolates were able to grow in ammonia-free medium in the presence of N2. Nitrogenase activity under such conditions was demonstrated by the acetylene reduction test. The facultatively lithoautotrophic strain (AcRS1), a strain (AcRS2) with unusually large cells (2×5 μm), and a vibrio-shaped strain (AcRM3) are described as new Desulfobacter species, D. hydrogenophilus, D. latus, and D. curvatus, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00456706
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of inoculum rate on the performance of chickpea (Cicer arietinum L.) Rhizobium strains in the field (1987)
    Springer
    Biology and fertility of soils 5 (1987), S. 83-87 
    Details
    ISSN: 1432-0789
    Keywords: Inoculation ; Inoculum dose ; Nitrogen fixation ; Chickpea ; Rhizobium spp. ; Cicer arietinum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The influence of three inoculum rates on the performance of three chickpea (Cicer arietinum L.) Rhizobium strains was examined in the field on a Mollisol soil. Increasing amounts of inoculum improved the performance of the strains. A normal dose (104 cells per seed) applied at different intervals gave non-significant increases in nodulation, nitrogenase activity (acetylene reduction assay), nitrogen uptake and grain yield. A ten-fold increase in inoculum increased nodule number, shoot dry weight, nitrogenase activity (ARA) and grain yield, but increases over the control were significant only for nodule dry weight and nitrogen uptake by shoot and grain. The highest level of inoculum (100 × normal) significantly increased nodule dry weight, grain yield, total nitrogenase activity (ARA) and nitrogen uptake by shoot and grain. Strain TAL 620 was more effective than the other two. Combined nitrogen (60 kg N ha−1) suppressed nodulation and nitrogenase activity (ARA).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264351
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  • 7
    Electronic Resource
    Electronic Resource
    The calcium requirement for functional vesicle development and nitrogen fixation by Frankia strains EAN1pec and CpI1 (1987)
    Springer
    Archives of microbiology 149 (1987), S. 24-29 
    Details
    ISSN: 1432-072X
    Keywords: Frankia ; Nitrogen fixation ; Calcium ; Vesicle development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A calcium requirement was shown for both vesicle development and nitrogenase activity by Frankia strains EAN1pec and CpI1. Washing cells with EGTA or EDTA inhibited both vesicle development and nitrogenase activity. The inhibition of both was reversed by the addition of calcium. A variety of agents known to affect calcium-dependent biological processes, such as a Ca-ATPase inhibitor, Ca-channel blockers, Ca-ionophores, calmodulin antagonists and the local anaesthetics, tetracaine and dibucaine, inhibited nitrogenase activity. Respiratory studies showed that a CN-insensitive respiration process occurred only under nitrogen derepressing conditions. Respiration by NH4Cl-grown cells was completely inhibited by KCN while N2-grown cells were inhibited by only 70%. Removal of calcium ions by EGTA or by the addition of dibucaine or tetracaine blocked the CN-insensitive respiration. This CN-insensitive respiration may be involved in protecting nitrogenase inside the vesicles from oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00423131
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  • 8
    Electronic Resource
    Electronic Resource
    Nitrogen-fixing stem nodules on Aeschynomene afraspera (1987)
    Springer
    Biology and fertility of soils 4 (1987), S. 61-66 
    Details
    ISSN: 1432-0789
    Keywords: Stem nodulation ; Aeschynomene afraspera ; Legume ; Nitrogen fixation ; Acetylene reduction assay (ARA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Aeschynomene afraspera is a wild annual legume growing in periodically waterlogged soils in western Africa. This legume is characterized by a profuse stem nodulation. Nodules are formed on the stem at the emergence of lateral root primordia, called nodulation sites. These sites are irregularly distributed on vertical rows all along the stem and branches. Stem nodules are hemispherically shaped. Their outside is dark green and they contain a red-pigmented central zone. Stem nodules exhibit a high nitrogen-fixing potential. Acetylene reduction assays result in stem nodule activity of 309 μmol C2H4 g−1 dry nodule h−1. Field-grown stem nodulated Aeschynomene accumulated more N (51 g N m−2 in 10 weeks) than the root nodulated one. Because of this nitrogenfixing potential and its ability to grow in waterlogged conditions, A. afraspera could probably be introduced into tropical rice cropping systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280352
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  • 9
    Electronic Resource
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    Yield response of spring wheat cultivars (Triticum aestivum and T. turgidum) to inoculation with Azospirillum brasilense under field conditions (1987)
    Springer
    Biology and fertility of soils 4 (1987), S. 27-35 
    Details
    ISSN: 1432-0789
    Keywords: Triticum aestivum ; T. turgidum ; Nitrogen fixation ; Field inoculation ; Acetylene reduction assay (ARA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Eight commercial Israeli spring wheat cultivars (six Triticum aestivum and two T. turgidum) grown with 40 and 120 kg N/ha were tested for responses to inoculation with Azospirillum brasilense. At the low level of N fertilization (40 kg/ha), five cultivars showed significant increases in plant dry weight measured at the milky ripe stage; however, by maturation only the cultivar “Miriam” showed a significant increase in grain yield. Two cultivars, which had shown a positive inoculation effect at the earlier stages, had a significant decrease in grain yield. No significant effect of inoculation was found at the high N level. To confirm those results, four wheat (T. aestivum) cultivars were tested separately over 4 years in 4 different locations under varying N levels. Only Miriam showed a consistently positive effect of Azospirillum inoculation on grain yield. Inoculation increased the number of roots per plant on Miriam compared with uninoculated plants. This effect was found at all N levels. Nutrient (N, P and K) accumulation and number of fertile tillers per unit area were also enhanced by Azospirillum, but these parameters were greatly affected by the level of applied N. It is suggested that the positive response of the spring wheat cultivar “Miriam” to Azospirillum inoculation is due to its capacity to escape water stresses at the end of the growth season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280347
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  • 10
    Electronic Resource
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    Nitrogen fixation and balance studies of rice soil (1987)
    Springer
    Biology and fertility of soils 4 (1987), S. 15-19 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen fixation ; N-balance studies ; Azolla ; Blue-green algae ; Chemical N fertilization ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A nitrogen balance study conducted in ceramic pots under net house conditions for four seasons showed that flooded rice soil leaves a positive nitrogen balance (N increase) in soil after rice cropping in both fertilized and unfertilized soil. Recovery of nitrogen from rice soil was more than its input in unfertilized soil, but it was reverse in fertilized soil. Incorporation of Azolla or BGA twice as basal and 20 days after transplanting (DAT) alone or in combination showed higher nitrogen balance and N2-fixation (N gain) in soil than in that where it was applied once either as basal or 20 DAT. Planted soil showed more N2-fixation than that of fallow rice, and flooded soil fixed more nitrogen in comparison to non-flooded soil in light but less in dark. Soil exposed to light fixed more nitrogen than that of unexposed soil in both flooded and non-flooded conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280345
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  • 11
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    Stimulation of root exudation of rice seedlings by Azospirillum strains: carbon budget under gnotobiotic conditions (1987)
    Springer
    Biology and fertility of soils 4 (1987), S. 9-14 
    Details
    ISSN: 1432-0789
    Keywords: Rhizosphere ; Nitrogen fixation ; Root exudates ; Soil bacteria ; Carbon budget ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The association of rice seedlings (cv. Delta) with different strains of Azospirillum was studied under monoxenic conditions in the dark. Axenic 3-day-old seedlings were obtained on a C- and N-free medium and inoculated with 6 · 107 bacteria per plant in a closed vial. Seven days later, different components of a carbon budget were evaluated on them and on sterile controls: respired CO2, carbon of shoot and roots, bacterial and soluble carbon in the medium. Two strains (A. lipoferum 4B and A. brasilense A95) isolated from the rhizosphere of rice caused an increase in exudation, + 36% and + 17% respectively compared with sterile control. Shoot carbon incorporation and respiration were reduced by inoculation. A third strain (A. brasilense R07) caused no significant change in exudation. A. lipoferum B7C isolated from maize did not stimulate rice exudation either. We further investigated a possible effect of nitrogen fixation on this phenomenon: inhibition of nitrogen fixation by 10% C2H2 did not modify the extent of C exudation by rice associated with A. lipoferum 4B or with the non-motile A. lipoferum 4T.
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    URL: http://dx.doi.org/10.1007/BF00280344
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  • 12
    Electronic Resource
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    The relationship between hydrogen metabolism, sulfate reduction and nitrogen fixation in sulfate reducers (1987)
    Springer
    Journal of industrial microbiology and biotechnology 1 (1987), S. 383-388 
    Details
    ISSN: 1476-5535
    Keywords: Sulfate-reducing bacteria ; Hydrogen metabolism ; Nitrogen fixation ; Deuterium-proton exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Hydrogenase and nitrogenase activities of sulfate-reducing bacteria allow their adaptation to different nutritional habits even under adverse conditions. These exceptional capabilities of adaptation are important factors in the understanding of their predominant role in problems related to anaerobic metal corrosion. Although the D2−H+ exchange reaction indicated thatDesulfovibrio desulfuricans strain Berre-Sol andDesulfovibrio gigas hydrogenases were reversible, the predominant activity in vivo was hydrogen uptake. Hydrogen production was restricted to some particular conditions such as sulfate or nitrogen starvation. Under diazotrophic conditions, a transient hydrogen evolution was followed by uptake when dinitrogen was effectively fixed. In contrast, hydrogen evolution proceeded when acetylene was substituted as the nitrogenase substrate. Hydrogen can thus serve as an electron donor in sulfate reduction and nitrogen metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569336
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  • 13
    Electronic Resource
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    Nitrogen cycling in an Antarctic ecosystem 2. Estimation of the amount of nitrogen fixation in a moss community on East Ongul Island (1987)
    Springer
    Ecological research 2 (1987), S. 31-40 
    Details
    ISSN: 1440-1703
    Keywords: Acetylene reduction ; Antarctica ; Cyanobacteria ; Moss community ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen fixation by cyanobacteria in a moss community on East Ongul Island (69°00'S 39°35'E), Antarctica was investigated using the acetylene reduction method. The mean acetylene reduction rate at 10°C and 200 μE·m−2·s−1 photosynthetically active radiation was 7.12 nmol C2H4 per square centimeter of moss community per hour. The effects of temperature, radiation, desiccation and rehydration on the acetylene reduction rates were examined. A simple predictive model was constructed in order to estimate the amount of nitrogen fixed in the field. Using this model, the daily amount of nitrogen fixation was calculated from microclimatic data (temperature and radiation) measured in the experimental field at Syowa Station on East Ongul Island between 1983 and 1984. The cumulative amount of nitrogen fixation in the growing season during this period was estimated to be 329 mg N per square meter of moss community. It is suggested that nitrogen fixation by cyanobacteria in the moss community is important as a nitrogen source for the community growth on East Ongul Island.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02348617
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  • 14
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    Effects of delayed soil and foliar N fertilization on yield and N2 fixation of soybean (1987)
    Springer
    Plant and soil 97 (1987), S. 361-368 
    Details
    ISSN: 1573-5036
    Keywords: Foliar fertilization ; Fertilizer uptake efficiency ; Late fertilization ; Nitrogen-15 ; Nitrogen fixation ; Nitrogen translocation ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field experiments were conducted to determine the effects of the amount, time and method of fertilizer N application on the efficiency of N uptake, N2 fixatio and yield of soybean. Soil and foliar fertilizer N, applied during the pod-filling stage were absorbed by plants with equal and high efficiency, compared to an appreciably lower utilization efficiency for N applied before seedling emergence. These results reveal that the soybean roots were active in N uptake during these late stages of growth. Nitrogen fertilization during pod-filling resulted in significant yield increases over the control treatment which received an early application of 20 Kg N/ha. Seed yield increases were, however, more pronounced than total dry matter yield, and virtually all of the late-applied N was translocated into the pods. Nitrogen fixation in soybean was not influenced by the application of 40 kg N/ha to plants as soil or foliar N during the pod-filling stage. However, 80 kg N/ha supplied during pod-filling as 40 kg soil plus 40 kg foliar N/ha significantly reduced the amount of N2 fixed. The results obtained in these studies suggest that inadequate N supply during pod-filling limited soybean yields, and that by the judicious application of fertilizer N during the late stages of growth, it was possible to enhance soybean yields without necessarily inhibiting N2 fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02383226
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  • 15
    Electronic Resource
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    Use of Azolla as a test organism in a growth chamber of simple design (1987)
    Springer
    Plant and soil 99 (1987), S. 219-230 
    Details
    ISSN: 1573-5036
    Keywords: Azolla ; Blue green alga ; Evapo-transpiratio chamber ; Humidity ; Light condition ; Nitrogen fixation ; Plant environment ; Symbiotic system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The construction and application of a new type of growth chamber, in which different growth conditionsi.e.: temperature, humidity, pH, light intensity, light colour, change in nutrient composition and gas exchange can easily be controlled, are presented. The method has previously been applied to twoAzolla speciesviz. Azolla filiculoides, which is cold tolerant andAzolla pinnata (distinguished in Vietnam as the form Xanh), which is heat tolerant. In the growth chamber natural growth conditions of the Azolla —Anabaena azollae symbiotic association were imitated as much as possible. For testing the system, methods discussed earlier8,14 and some previously presented data, concerning photosynthetic activities, such as oxygen evolution and nitrogen fixation (acetylene reduction) of twoAzolla species39, were partially used. Biomass ofA. filiculoides was measured and reactions to its environment at conditions when grown in the field and in the growth chamber, were studied. Growth and photosynthesis measurements were performed under special light conditions and with whole plants grown under laboratory conditions. Anthocyanin synthesis was studied in relation with humidity. Anthocyanin spectra were analyzed by means of a spectrum-deconvolution method.
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    URL: http://dx.doi.org/10.1007/BF02370869
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  • 16
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    Metabolism and translocation of fixed nitrogen in the nodulated legume (1987)
    Springer
    Plant and soil 100 (1987), S. 157-169 
    Details
    ISSN: 1573-5036
    Keywords: Legume ; Nitrogen fixation ; Nodule ; Translocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogen (N2) fixed by Rhizobium bacteroids in the legume nodule is excreted as ammonia to the surrounding host cell where it is efficiently assimilated into the amide group of glutamine. Generally glutamine is a minor exported solute of nitrogen, being further metabolised to asparagine in temperate species and to the ureides, allantoin and allantoic acid in tropical species. These solutes serve as the principal translocated forms of nitrogen in xylem. Compartmentalisation of the pathways of nitrogen metabolism and the role of ammonia in regulation of their activity is examined in nodules of both asparagine-forming (Lupinus albus L.) and ureide-forming (Vigna unguiculata L. Walp) symbioses.
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    URL: http://dx.doi.org/10.1007/BF02370939
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  • 17
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    Co-evolution of the legume-Rhizobium association (1987)
    Springer
    Plant and soil 100 (1987), S. 171-181 
    Details
    ISSN: 1573-5036
    Keywords: Co-evolution ; Gene pool ; Nitrogen fixation ; Pisum sativum L. ; Rhizobium leguminosarum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A number of examples is given demonstrating the co-existence of pea genotypes and their specific Rhizobium, strains isolated within the same region.R. leguminosarum strains compatible with the cultivated pea have a narrow symbiotic range and they are widely distributed in European soils. This is presumably due to the narrow genetic base of the cultivated pea and its wide-spread cultivation in European soils. Rhizobium strains capable of nodulating a primitive pea line from Afghanistan were only found in soils of the Middle East and Central Asia. A more restricted distribution of specific Rhizobium strains was found for fulvum peas from Israel. Rhizobium strains effective with the fulvum pea were found in Israeli soils. A good example of co-evolution due to geographical isolation was found in south Turkey. Here a pea line was found which can form an effective symbiosis with local Rhizobium strains but not with strains from other parts of Turkey.
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    URL: http://dx.doi.org/10.1007/BF02370940
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  • 18
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    Endophyte transmission and activity in the Anabaena-Azolla association (1987)
    Springer
    Plant and soil 100 (1987), S. 183-212 
    Details
    ISSN: 1573-5036
    Keywords: Anabaena azollae ; Azolla ; Desiccation ; Macrosporocarps ; Microsporocarps ; Nitrogen fixation ; Sexual reproduction ; Survival Azolla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The survival of Azolla was studied in an artificial system which simulated the soil/water interface and the desiccation of soil during a fallow period in lowland rice culture. Tests with non-sporulating and sporulating Azolla fronds showed that Azolla only survives with sporulated fronds. At their reappearance the Azolla fronds already harboured the Anabaena endophyte. A detailed light microscopic and transmission electron microscopic study of macro- and micros-porocarp formation and development revealed that the endophyte is transmitted by the macrosporocarps and not by the microsporocarps. The Anabaena cells within the macrosporocarps are found just below the indusium cap. These cells are not nitrogen-fixing akinetes. The free-living Anabaena cells at the stem apex and below the overarching developing leaves do not bear heterocysts and accordingly are non nitrogen-fixing. During the development of the leaf the Anabaena enters the leaf cavity, but later the pore of this, cavity closes and the imprisoned cyanobacteria are lysed before the leaf decays. As the Azolla leaves age a nitrogen-fixing capability is successively built up concomittantly with the production of heterocysts. Heterocyst frequencies of 40–50% can be found inAnabaena azollae. Usually a gradient of nitrogen-fixing capacity occurs along the Azolla rhizome with two distinct peaks at leaf number 7/8 and at leaf number 13/14 from the apex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02370941
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  • 19
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    Total and CO-reactive heme content of actinorhizal nodules and the roots of some non-nodulated plants (1987)
    Springer
    Plant and soil 100 (1987), S. 225-236 
    Details
    ISSN: 1573-5036
    Keywords: Actinorhizae ; Alnus ; Casuarina ; Frankia ; Hemoglobin ; Myrica ; Nitrogen fixation ; Root nodules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The concentration of total and CO-reactive heme was measured in actinorhizal nodules from six different genera. This gave the upper limit to hemoglobin concentration in these nodules. Quantitative extraction of CO-reactive heme was achieved under anaerobic conditions in a buffer equilibrated with CO and containing Triton X-100. The concentration of CO-reactive heme in nodules of Casuarina and Myrica was approximately half of that found in legume nodules, whereas in Comptonia, Alnus and Ceanothus the concentrations of heme were about 10 times lower than in legume nodules. There was no detectable CO-reactive heme in Datisca nodules, but low concentrations were detected in roots of all non-nodulating plants examined, includingZea mays. Difference spectra of CO treated minus dithionite-reduced extracts displayed similar wavelengths of maximal and minimal light absorption for all extracts, and were consistent with those of a hemoglobin. The concentration of CO-reactive heme was not correlated to the degree to which CO inhibited nitrogenase activity nor was it affected by reducing the oxygen concentration in the rooting zone. However, there was a positive correlation between heme concentration and suberization or lignification of the walls of infected host cells. These observations demonstrate that, unlike legume nodules, high concentrations of heme or hemoglobin are not needed for active nitrogen fixation in most actinorhizal nodules. Nonetheless, a significant amount of CO-reactive heme is found in the nodules of Alnus, Comptonia, and Ceanothus, and in the roots ofZea mays. The identity and function of this heme is unknown.
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    URL: http://dx.doi.org/10.1007/BF02370943
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    Species variation in the fixation and transfer of nitrogen from legumes to associated grasses (1987)
    Springer
    Plant and soil 98 (1987), S. 265-274 
    Details
    ISSN: 1573-5036
    Keywords: Alfalfa ; Birdsfoot trefoil ; Bromegrass ; Nitrogen fixation ; Nitrogen transfer ; Orchardgrass ; Red clover ; Red fescue ; Tall fescue ; Timothy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Three legume species (alfalfa, red clover, and birdsfoot trefoil) in combination with five grass species (timothy, bromegrass, red fescue, tall fescue, and orchardgrass) were used to study N transfer in mixtures, using the 15N dilution technique. The advantage of grass-legume mixtures was apparent. Total herbage and protein yields of grasses in mixtures were higher than those alone, especially at the later cuts. This benefit of mixed cropping is mainly due to N transfer from legumes to associated grasses. N2-fixation and N transfer by alfalfa rated highest, red clover intermediate, and birdsfoot trefoil lowest. The importance of each pathway of N transfer from legumes appeared to differ between species. Alfalfa and red clover excreted more N than trefoil, while the latter contributed more N from decomposition of dead nodule and root tissue. The greatest advantage from a grass-legume mixture, with respect to the utilization of N released from the legume, varied with early maturing tall fescue (Kentucky 31), orchardgrass (Juno), and bromegrass (Tempo), to intermediate timothy (Climax), and least with late maturing red fescue (Carlawn).
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    URL: http://dx.doi.org/10.1007/BF02374830
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  • 21
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    Nodulation, nitrogen fixation and nitrogen uptake in pigeonpea (Cajanus cajan (L.) Millsp) of different maturity groups (1987)
    Springer
    Plant and soil 99 (1987), S. 255-266 
    Details
    ISSN: 1573-5036
    Keywords: Cajanus cajan ; Maturity groups ; Nitrogenase activity ; Nitrogen fixation ; Nitrogen uptake ; Nodulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The seasonal patterns of nodulation, acetylene reduction, nitrogen uptake and nitrogen fixation were studies for 11 pigeonpea cultivars belonging to different maturity groups grown on an Alfisol at ICRISAT Center, Patancheru, India. In all cultivars the nodule number and mass increased to a maximum around 60–80 days after sowing and then declined. The nodule number and mass of medium- and late-maturing cultivars was greater than that of early-maturing cultivars. The nitrogenase activity per plant increased to 60 days after sowing and declined thereafter, with little activity at 100 days when the crop was flowering. At later stages of plant growth nodules formed down to 90 cm below the soil surface but those at greater depth appeared less active than those near the surface. All the 11 cultivars continued to accumulate dry matter until 140 days, with most biomass production by the late-maturing cultivars (up to 11 t ha−1) and least by the early-maturing determinate cultivars (4 t ha−1). Total nitrogen uptake ranged from 69 to 134 kg ha−1. Nitrogen fixation by pigeonpea was estimated as the difference in total nitrogen uptake between pigeonpea and sorghum and could amount to 69 kg N ha−1 per season, or half the total nitrogen uptake. Fixation by pigeonpea increased with crop duration, but there were differences within each maturity group. The limitations of the methods used for estimating N2 fixation by pigeonpea are discussed.
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    URL: http://dx.doi.org/10.1007/BF02370872
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    A study of nodulation and nitrogen fixation of alder on the purplish soils in China (1987)
    Springer
    Plant and soil 99 (1987), S. 285-290 
    Details
    ISSN: 1573-5036
    Keywords: Alder ; Actinomyces ; Nodulation ; Nitrogen fixation ; Purplish soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The alder has a perennial nodule cluster. The nodule amount on the roots increases with tree age. The N2-fixing activity of nodules decreases with nodule age. Purple coloured soils with various soil pHs and CaCO3 contents are, in the main, the ones which influence nodulation and N2-fixing. Higher N2-fixing capacity existed in the neutral and low calcium soils. High calcium soils and acid soils can restrain nodulation and the N2-fixing rate significantly. On the slope, where calcarous light loams are found, the annual nitrogen fixation capacity of alder and cypress mixed plantations, less than 10 years old, is 16 or 17 kg/ha yr, but in the valley, a pure alder plantation can reach 40 kg/ha yr.
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    URL: http://dx.doi.org/10.1007/BF02370875
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    Nodulation and symbiotic nitrogen fixation of cowpea (Vigna unguiculata (L.) Walp) (1987)
    Springer
    Plant and soil 99 (1987), S. 435-439 
    Details
    ISSN: 1573-5036
    Keywords: Cowpea ; Effective nodulation ; Nitrogen fixation ; Nodule growth ; Plant age ; Rhizobium strain ; Vigna unguiculata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Rhizobium strains CIAT 301, CIAT 79 and SLM 602 were tested and found effective in the nodulation and nitrogen fixation of cowpea cv. MI-35 (Vigna unguiculata (L.) Walp) plants in growth chamber experiments. Fresh weight of nodules increased with plant age initially and stabilized in 20–30 days from planting, followed by a secondary flush of nodule growth after 30 days. Apparent nitrogen fixation per gram nodule fresh weight reached a maximum in 20–30 days after planting and then decreased, even though a flush of new nodules was produced.
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    URL: http://dx.doi.org/10.1007/BF02370888
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    Nitrogen-fixing (acetylene-reducing) bacteria associated with ectomycorrhizae of Douglas-fir (1987)
    Springer
    Plant and soil 98 (1987), S. 425-428 
    Details
    ISSN: 1573-5036
    Keywords: Diazotrophs ; Ectomycorrhizae ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogenase activity, measured by acetylene reduction, was detected on nursery-grown, surface-sterilized ectomycorrhizae of Douglas-fir, formed withLaccaria laccata, Hebeloma crustuliniforme, Rhizopogon vinicolor, andThelephora sp. Detached mycorrhizae were incubated in nitrogen-free liquid medium under microaerophilic conditions. Nitrogenase activity was attributed toClostridium spp. andAzospirillum spp.
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    URL: http://dx.doi.org/10.1007/BF02378363
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  • 25
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    Field measurement of symbiotic nitrogen fixation in an established lucerne ley using15N and an acetylene reduction method (1987)
    Springer
    Plant and soil 97 (1987), S. 93-104 
    Details
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Lucerne ; Medicago sativa ; 15N methodology ; Nitrogen fixation ; Quantitative estimation ; Seasonal pattern
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Lucerne is an important forage legume in the south and south-east of Sweden on well-drained soils. However, data is lacking on the apparent amount of nitrogen derived through N2 fixation by field-grown lucerne. This report provides basic information on the subject. The experiment was performed in a lucerne ley grown 40 km north of Uppsala. The input of nitrogen through fixation to the above-ground plant material of an established lucerne (Medicago sativa L.) ley was estimate by15N methodology during two successive years. The amount of fixed N was 242 kg N ha−1 in 1982 and 319 kg N ha−1 in 1983. The proportion of N derived from the atmosphere (%Ndfa) was 70% and 80% for the two years respectively. The first harvest in both years contained a lower proportion fixed N. Both N2 fixation and dry matter production were enhanced during the second year, particularly in the first harvest. The Ndfa was 61% in the first harvest in 1982, compared to 72% Ndfa during the same period in 1983. This demonstrates the strong influence of environment on both dry matter production and N2 fixation capacity of the lucerne. In addition anin situ acetylene reduction assay was used in 1982 to measure the seasonal distribution of the N2 fixation and in 1983 to study the effect of soil moisture on the N2 fixation process. The seasonal pattern showed great dependence on physiological development and harvest pattern of the lucerne ley. The maximum rate of N2 fixation occurred at the bud or early flower stage of growth and was followed by a rapid decline as flowering proceeded. After harvest the nitrogenase activity markedly decreased and remained low during at least two weeks until regrowth of new shoots began. Irrigation doubled the nitrogenase activity of the lucerne in late summer 1983, when soil moisture content in the top soil was near wilting point. No changes in nitrogenase activity did occur in response to watering earlier during the summer, when the soil matric potential was around −0.30 MPa.
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    URL: http://dx.doi.org/10.1007/BF02149828
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    Cloning and characterization of nifA and ntrC genes of the stem nodulating bacterium ORS571, the nitrogen fixing symbiont of Sesbania rostrata: Regulation of nitrogen fixation (nif) genes in the free living versus symbiotic state (1987)
    Springer
    Molecular genetics and genomics 206 (1987), S. 207-219 
    Details
    ISSN: 1617-4623
    Keywords: Azorhizobium sesbaniae ORS571 ; Nitrogen fixation ; Regulation ; Tn5 mutagenesis ; lacZ fusions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A cosmid bank of ORS571, a diazotrophic bacterium capable of inducing aerial stem and root nodules on Sesbania rostrata, was constructed in the vector pLAFR1. A DNA probe carrying the Klebsiella pneumoniae nifA gene was used to identify nifA-and ntrC-like regions of ORS571 in the cosmid bank by colony hybridization. Cosmids carrying these regions were mapped by restriction endonuclease analysis, Southern blotting and transposon Tn5 mutagenesis. Selected Tn5 insertion mutations in the nifA/ntrC homologous regions were used for gene-replacement experiments and the resulting ORS571 mutants were examined for Nif, Fix and Ntr phenotypes. Two clearly distinct regulatory loci were thus identified and named nifA and ntrC. Plasmids carrying gene fusions of the ORS571 nifH and nifD genes to lacZ were constructed and the regulation of the ORS571 nifHDK promoter, and of the Rhizobium meliloti nifHDK promoter, was studied under varying physiological conditions in ORS571, ORS571 nifA::Tn5 and ORS571 nitrC::Tn5 strains. A model for the role of nifA and ntrC in the regulation of ORS571 nif and other nitrogen assimilation genes is proposed.
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    URL: http://dx.doi.org/10.1007/BF00333576
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    Sequence of psi, a gene on the symbiotic plasmid of Rhizobium phaseoli which inhibits exopolysaccharide synthesis and nodulation and demonstration that its transcription is inhibited by psr, another gene on the symbiotic plasmid (1987)
    Springer
    Molecular genetics and genomics 207 (1987), S. 149-154 
    Details
    ISSN: 1617-4623
    Keywords: Beans ; DNA Sequence ; Gene regulation ; Nitrogen fixation ; Nodulation ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A gene termed psi (polysaccharide inhibition), located close to the nodulation genes of the Rhizobium phaseoli symbiotic plasmid pRP2JI inhibited exopolysaccharide synthesis (EPS) and nodulation ability (Nod) in Rhizobium when it was cloned in a multicopy plasmid. The sequence of psi showed that it specified a polypeptide of mol. wt. 10000 that may be associated with the membrane of Rhizobium. A second gene, psr (polysaccharide restoration), was located on pRP2JI. When cloned in multicopy plasmids, psr overcame the EPS and Nod defects in strains carrying multicopy psi. Strains with multicopy psr induced non-fixing nodules on Phaseolus beans. Using gene fusions between psi and lacZ, it was shown that psi inhibited transcription of psr.
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    Biochemical and genetic analysis of the nifHDKE region of Rhizobium ORS571 (1987)
    Springer
    Molecular genetics and genomics 207 (1987), S. 280-287 
    Details
    ISSN: 1617-4623
    Keywords: Rhizobium ; Nitrogen fixation ; Nif products ; Tn5 mutagenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Deletions and Tn5 insertions were obtained in a cloned 10 kb BamHI-BglII fragment carrying the nifHDKE region of Rhizobium ORS571 and were recombined into the host genome. Genetic analysis of the mutants, comparison of polypeptides synthesized under conditions of repression and depression of N2 fixation, and biochemical complementation of crude extracts were performed. All Nif- mutants were also Fix-. Three transcription units were identified, nifHDK, nifE and a new nif locus adjacent to nifE; no nif locus was found in the immediate vicinity upstream of nifH. Fifteen polypeptides synthesized under conditions of N2 fixation were characterized by two-dimensional gel electrophoresis. Ten of them are likely to be nif products and polypeptides encoded by nifH, nifD, nifK and tentatively nifE were identified. Physiological and biochemical evidence for the functioning of the second copy of nifH is reported. Nitrogenase component 2 synthesized by this copy could not be differentiated from component 2 synthesized in the wild-type strain. When the function of nifH copy 1 was abolished, the amount of component 2 synthesized was about 30% of that synthesized in the wild-type strain.
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    URL: http://dx.doi.org/10.1007/BF00331590
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    Identification of nifE-, nifN- and nifS-like genes in Bradyrhizobium japonicum (1987)
    Springer
    Molecular genetics and genomics 207 (1987), S. 503-508 
    Details
    ISSN: 1617-4623
    Keywords: Bradyrhizobium ; Nif genes ; Nitrogen fixation ; Root nodule symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The 17 kb region between the Bradyrhizobium japonicum nitrogenase genes (nifDK and nifH) was investigated for the presence of further nif or fix genes by site-directed insertion or deletion/replacement mutagenesis and interspecies hybridization. Mutant strains were tested for their ability to reduce acetylene in free-living, microaerobic culture (Nif phenotype) and in soybean root nodules (Fix phenotype). The presence of a gene, previously identified by hybridization with the Klebsiella pneumoniae nifB gene, was proved by isolation of a nifB insertion mutant which was completely Nif- and Fix-. Three other regions were found to be homologous to the K. pneumoniae genes nifE, nifN, and nifS, NifE and nifN insertion mutants were completely Nif-/Fix- whereas nifS mutants were leaky with 30% residual Fix activity. Taken together, the data show that the B. japonicum genome harbours a cluster of closely adjacent genes which are directly concerned with nitrogenase function.
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    URL: http://dx.doi.org/10.1007/BF00331622
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    Direct response of Bradyrhizobium japonicum nifA-mediated nif gene regulation to cellular oxygen status (1987)
    Springer
    Molecular genetics and genomics 209 (1987), S. 621-626 
    Details
    ISSN: 1617-4623
    Keywords: Bradyrhizobium japonicum ; nifA gene ; Nitrogen fixation ; Oxygen control ; Transcriptional control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nifA genes of Klebsiella pneumoniae and Bradyrhizobium japonicum were constitutively expressed from the pBR329-derived chloramphenicol resistance promoter. The inserts of these nifA plasmid constructs were devoid of any other intact flanking genes. The nifA genes thus expressed led to a marked activation of a B. japonicum nifD-lacZ fusion under microaerobic conditions. Under aerobic growth conditions, however, activation was mediated only by the K. pneumoniae nifA gene but not by the B. japonicum nifA gene. This selective effect was observed in both the Escherichia coli as well as the B. japonicum backgrounds. Several lines of evidence suggest that in these experiments oxygen adversely affects B. japonicum nifA-dependent nif gene regulation at the post-transcriptional level, probably even at the post-translational level, and that this effect does not require a nifL-like gene. Models are proposed in which oxygen inhibits the B. japonicum NifA protein either directly or indirectly via other cellular components involved in general protein oxidation pathways.
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    URL: http://dx.doi.org/10.1007/BF00331174
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    Identification and cloning of nodulation genes from the stem-nodulating bacterium ORS571 (1987)
    Springer
    Molecular genetics and genomics 206 (1987), S. 291-299 
    Details
    ISSN: 1617-4623
    Keywords: Nitrogen fixation ; Stem nodulation ; Tn5 mutagenesis ; nod genes ; nodC homology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary After random Tn5 mutagenesis of the stem-nodulating Sesbania rostrata symbiont strain ORS571, Nif-, Fix- and Nod- mutants were isolated. The Nif- mutants had lost both free-living and symbiotic N2 fixation capacity. The Fix- mutants normally fixed N2 in the free-living state but induced ineffective nodules on S. rostrata. They were defective in functions exclusively required for symbiotic N2 fixation. A further analysis of the Nod- mutants allowed the identification of two nod loci. A Tn5 insertion in nod locus 1 completely abolished both root and stem nodulation capacity. Root hair curling, which is an initial event in S. rostrata root nodulation, was no longer observed. A 400 bp region showing weak homology to the nodC gene of Rhizobium meliloti was located 1.5 kb away from this nod Tn5 insertion. A Tn5 insertion in nod locus 2 caused the loss of stem and root nodulation capacity but root hair curling still occurred. The physical maps of a 20.5 kb DNA region of nod locus 1 and of a 40 kb DNA region of nod locus 2 showed no overlaps. The two nod loci are not closely linked to nif locus 1, containing the structural genes for the nitrogenase complex (Elmerich et al. 1982).
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    Klebsiella pneumoniae nif-lac fusions are expressed in Agrobacterium tumefaciens C58 (1987)
    Springer
    Molecular genetics and genomics 206 (1987), S. 460-464 
    Details
    ISSN: 1617-4623
    Keywords: Agrobacterium tumefaciens ; Klebsiella pneumoniae ; Nitrogen fixation ; Gene fusions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plasmids containing hybrid genes, in which different Klebsiella pneumoniae nif (nitrogen-fixation) promoters were fused with the structural part of the Escherichia coli lac operon, were introduced into a double auxotrophic derivative of Agrobacterium tumefaciens C58. A study of their expression in the new host was made simple by the inherent inability of A. tumefaciens C58 to produce β-galactosidase unless provided with the wild-type lac operon of E. coli. As shown by quantitative measurements of the enzyme, all K. pneumoniae promoters were expressed well in A. tumefaciens C58, even under conditions known to repress them. It also has been shown that the activity of K. pneumoniae nif A is essential for the expression of nifHDK even when introduced into A. tumefaciens. After entering the new host the plasmids, the nif genes and the fusion alleles contained in them, remained stable. Possible mechanisms responsible for the constitutive behaviour of nif promoters in A. tumefaciens are discussed.
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    Cloning of the gene for phosphoenolpyruvate carboxylase from Azotobacter chroococcum, an enzyme important in aerobic nitrogen fixation (1987)
    Springer
    Molecular genetics and genomics 208 (1987), S. 481-484 
    Details
    ISSN: 1617-4623
    Keywords: PEP carboxylase ; Azotobacter chroococcum ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Azotobacter chroococcum Fos 189 is a Tn1-induced mutant which, unlike the parent strain MCD1, does not fix nitrogen in air when provided with glucose or pyruvate as sole carbon sources. Fos 189 showed 5% of parental activity for phosphoenolpyruvate carboxylase though PEP synthetase activity was normal. The A. chroococcum phosphoenolpyruvate carboxylase (ppc) gene was isolated after complementation of an appropriate Escherichia coli mutant using a broad host range gene bank prepared from A. chroococcum genomic DNA. The gene was localised by transposon mutagenesis and subcloning on a minimum DNA fragment of 6.6 kb. Broad host range plasmids containing the A. chroococcum ppc gene complemented the mutation in Fos 189 thereby restoring aerotolerant nitrogen fixation.
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    URL: http://dx.doi.org/10.1007/BF00328143
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    Transposon-induced symbiotic mutants of Bradyrhizobium japonicum: Isolation of two gene regions essential for nodulation (1987)
    Springer
    Molecular genetics and genomics 207 (1987), S. 15-23 
    Details
    ISSN: 1617-4623
    Keywords: Bradyrhizobium japonicum ; Transposon Tn5 ; Mutants ; Nodulation ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two strains of the soybean endosymbiont Bradyrhizobium japonicum, USDA 110 and 61 A101 C, were mutagenized with transposon Tn5. After plant infection tests of a total of 6,926 kanamycin and streptomycin resistant transconjugants, 25 mutants were identified that are defective in nodule formation (Nod-) or nitrogen fixation (Fix-). Seven Nod- mutants were isolated from strain USDA 110 and from strain 61 A101 C, 4 Nod- mutants and 14 Fix- mutants were identified. Subsequent auxotrophic tests on these symbiotically defective mutants identified 4 His- Nod- mutants of USDA 110. Genomic Southern analysis of the 25 mutants revealed that each of them carried a single copy of Tn5 integrated in the genome. Three 61 A101 C Fix- mutants were found to have vector DNA co-integrated along with Tn5 in the genome. Two independent DNA regions flanking Tn5 were cloned from the three nonauxotrophic Nod- mutants and one His-Nod- mutant of USDA 110. Homogenotization of the cloned fragments into wild-type strain USDA 110 and subsequent nodulation assay of the resulting homogenotes confirmed that the Tn5 insertion was responsible for the Nod- phenotype. Partial EcoR1 restriction enzyme maps around the Tn5 insertion sites were generated. Hybridization of these cloned regions to the previously cloned nod regions of R. meliloti and nif and nod regions of B. japonicum USDA 110 showed no homology, suggesting that these regions represent new symbiotic clusters of B. japonicum.
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    Identification of two classes of Rhizobium phaseoli genes required for melanin synthesis, one of which is required for nitrogen fixation and activates the transcription of the other (1987)
    Springer
    Molecular genetics and genomics 207 (1987), S. 155-160 
    Details
    ISSN: 1617-4623
    Keywords: Gene regulation ; Melanin synthesis ; Nitrogen fixation ; Phaseolus beans ; Rhizobium phaseoli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The symbiotic plasmid pRP2JI of Rhizobium phaseoli strain 8002 was shown to contain two separate regions of DNA which are required and sufficient for the synthesis of the pigment melanin. One of these regions containing the class II mel gene(s) was located to other genes involved in nodulation and in nitrogen fixation. Mutations in this region abolished both the ability to synthesize melanin and to fix nitrogen in Phaseolus bean root nodules. Mutations in the other, unlinked region, containing class I mel gene(s), also abolished melanin synthesis but did not affect symbiotic nitrogen fixation. Transcriptional fusions between the class I mel gene and the Escherichia coli lacZ gene were constructed and it was demonstrated that the class II mel gene(s) activated their transcription in free-living culture. Further, strains containing the cloned regulatory class II gene(s) synthesized melanin when growing in minimal medium, in contrast to wild-type strains which became pigmented only in complete medium containing yeast extract and tryptone. It was shown by hybridization experiments that the regulatory mel gene was closely linked to or may correspond to the regulatory nifA gene; a fragment of R. phaseoli DNA which included the class II gene(s) of R. phaseoli hybridized to a previously identified nifA-like gene of R. leguminosarum, the species that nodulates peas.
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    Transformation and regeneration of the legume Lotus corniculatus: A system for molecular studies of symbiotic nitrogen fixation (1987)
    Springer
    Molecular genetics and genomics 207 (1987), S. 245-250 
    Details
    ISSN: 1617-4623
    Keywords: Agrobacterium rhizogenes ; Plant transformation ; Transgenic legumes ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A procedure for transformation and regeneration of the legume species Lotus corniculatus (Bird's-foot trefoil) has been developed. The Agrobacterium rhizogenes 15834 and 8196 strains were used to transform plant cells in wound site infections and transformed roots were propagated in vitro. Transformation was monitored by hybridization with pRi T-DNA sequences and by detection of agropine and mannopine. Transformation frequencies of up to 90% were obtained. Shoots spontaneously formed on hairy root cultures were excised, rooted and inoculated with Rhizobium. Root nodules formed on transformed plants had nitrogenase activities comparable to untransformed nodules. Transcript levels from the nodule-specific leghemoglobin genes and the constitutive ubiquitin genes were similar in transformed and untransformed root nodules. Transformed plants responded to R. loti and Bradyrhizobium sp. (Lotus) strains with phenotypes identical to phenotypes for untransformed plants.
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