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  • Nitrogen fixation
  • Springer  (32)
  • 1975-1979  (32)
  • 1925-1929
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  • 1
    ISSN: 1432-2048
    Schlagwort(e): Centrosema leghaemoglobin ; Nitrate reductase ; Nitrogen fixation ; Nitrogenase ; Vigna
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The sequence of events leading up to the establishment of symbiotic nitrogen-fixation were studied in two tropical legumes, Centrosema pubescens Benth, and Vigna unguiculata L. Walp. Parameters measured included fresh and dry weights, chlorophyll and leghaemoglobin contents, as well as the activities of NADH-nitrate reductase (EC 1.6.6.1), and nitrogenase (nitric-oxide reductase-EC 1.7.99.2) in plants that were inoculated with suitable rhizobia or which were watered with potassium nitrate. Dry weight and photosynthetic activity of both species followed the sigmoidal pattern which is characteristic of most plants. Growth was little different in either a qualitative or quantitative sense whether nitrogen was supplied as nitrate or through dinitrogen fixation. Although the biochemical sequence of events was dependent on the limiting sensitivities of the individual assays used, the data suggest that nitrate reductase is the first measurable enzymatic activity in the nodules (and roots), followed by acetylene reduction and leghaemoglobin in that order. It is possible therefore, that low levels of symbiotic nitrogen fixation occur in the nodules in the absence of leghaemoglobin. Nitrate reductase activity in C. pubescens nodules was negatively exponentially correlated with nitrogenase activity of the same nodules, suggesting a changing metabolism in old nodules. These data are discussed in terms of environmental and physical factors known to control nitrogen fixation.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1432-2048
    Schlagwort(e): Leguminosae ; Nitrate-reductase mutants ; Nitrogen fixation ; Nodulation ; Rhizobium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of nitrate on the symbiotic properties of nitrate-reductase-deficient mutants of a strain of cowpea rhizobia (32H1), and of a strain of Rhizobium trifolii (TA1), were examined; the host species were Macroptilium atropurpureum (DC.) Urb. and Trifolium subterraneum L. Nitrate retarded initial nodulation by the mutant strains to an extent similar to that found with the parent strains. It is therefore unlikely that nitrite produced from nitrate by the rhizobia, plays a significant role in the inhibition of nodulation by nitrate. Nitrite is an inhibitor of nitrogenase, and its possible production in the nodule tissue by the action of nitrate reductase could be responsible for the observed inhibition of nitrogen fixation when nodulated plants are exposed to nitrate. However, the results of this investigation show that nitrogen fixation by the plants nodulated by parent or mutant strains was depressed by similar amounts in the presence of nitrate. No nitrite was detected in the nodules. Nodule growth, and to a lesser extent, the nitrogenase specific activity of the nodules (μmol C2H4g−1 nodule fr. wt. h−1), were both affected by the added nitrate.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 107 (1976), S. 115-124 
    ISSN: 1432-072X
    Schlagwort(e): Alanine dehydrogenase ; Anabaena cylindrica ; Heterocysts ; Nitrogen fixation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The l-alanine dehydrogenase (ADH) of Anabaena cylindrica has been purified 700-fold. It has a molecular weight of approximately 270000, has 6 sub-units, each of molecular weight approximately 43000, and shows activity both in the aminating and deaminating directions. The enzyme is NADH/NAD+ specific and oxaloacetate can partially substitute for pyruvate. The K m app for NAD+ is 14 μM and 60 μM at low and high NAD+ concentrations, respectively. The K m app for l-alanine is 0.4 mM, that for pyruvate is 0.11 mM, and that for oxaloacetate is 3.0 mM. The K m app for NH 4 + varies from 8–133 mM depending on the pH, being lowest at high pH levels (pH 8.7 or above). Alanine, serine and glycine inhibit ADH activity in the aminating direction. The enzyme is active both in heterocysts and vegetative cells and activity is higher in nitrogen-starved cultures than in N2-fixing cultures. The data suggest that although alanine is formed by the aminating activity of ADH, entry of newly fixed ammonia into organic combination does not occur primarily via ADH in N2-fixing cultures of A. cylindrica. Ammonia assimilation via ADH may be important in cultures with an excess of available nitrogen. The deaminating activity of the enzyme may be important under conditions of nitrogen-deficiency.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 114 (1977), S. 197-201 
    ISSN: 1432-072X
    Schlagwort(e): Anabaena sp. ; Nitrogen fixation ; Heterocysts ; Cyanobacteria ; Marine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A marine filamentous cyanobacterium capable of rapid growth under N2-fixing conditions has been isolated from the Texas Gulf Coast. This organism appears to be an Anabaena sp. and has been given the strain designation CA. Cultures grown on mineral salts medium bubbled with 1% CO2-enriched air at 42°C show a growth rate of 5.6±0.1 generations per day with molecular nitrogen as the sole nitrogen source. This growth rate is higher than any other reported in the literature to date for heterocystous cyanobacteria growing on N2. Under similar growth conditions, 7.5 mM NH4Cl yields a growth rate of 6.6±0.1 generations per day while 7.5 mM KNO3 allows for a growth rate of 5.8±0.4 generations-day. Nitrogen-fixation rates, as measured by acetylene reduction, show maximum activity values in the range of 50–100 nmoles ethylene produced/minxmg protein. These values compare favorably with those obtained from heterotrophic bacteria and are much higher than values reported for other cyanobacteria. Growth experiments indicate that the organism requires relatively high levels of sodium and grows maximally at 42°C. Because of its high growth rate on N2, this newly isolated organism appears ideal for studying nitrogen metabolism and heterocyst development among the cyanobacteria.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 122 (1979), S. 153-159 
    ISSN: 1432-072X
    Schlagwort(e): Rhizobium japonicum ; Nitrogenase activity ; Nitrogen fixation ; Organic acids ; Cell-morphology ; Bacteroids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Rhizobium japonicum 61-A-101 grew and fixed nitrogen more effectively on media containing an organic acid and a pentose sugar than on media containing only one of these carbon sources. Peak specific activities in the range 10–15 nmol C2H4 · h-1 · mg protein-1 were found for these organisms in a spot of growth about 1 cm diameter on agar surfaces exposed to air. Increasing concentrations of the organic acids (succinate or malonate) in a medium containing arabinose resulted in longer lasting activity. The inclusion of a third carbon source, glycerol, gave activity which remained at the maximum from about the 8 to the 18 day after inoculation although no growth of the bacteria occurs during the last 8 or 10 days. At low concentration of organic acid l-arabinose was a much better carbon source for supporting nitrogenase activity of these organisms that the d-form. Both organic acids affected the morphology of the bacteria. Higher concentrations, especially of malonate, gave swollen and distorted cells. When bacteria growing on organic acid-containing agar plates were suspended and plated after appropriate dilution on yeast extract — mannitolglycerol agar there was heterogeneity of colony form, with up to 90% microcolonies after growth on high malonate concentrations. The effects of malonate may be correlated with characteristics of the bacteroid form inside the nodule which contains relatively high concentrations of organic acids, especially malonate.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 116 (1978), S. 113-118 
    ISSN: 1432-072X
    Schlagwort(e): Hydrogen evolution ; Hydrogenase ; Nodules ; Bacteroids ; Nitrogenase ; Rhizobium leguminosarum ; Acetylene reduction ; Nitrogen fixation ; Pisum sativum ; Legumes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Hydrogen evolution from root nodules has been reported to make N2 fixation by some legume-Rhizobium symbiotic systems inefficient. We have surveyed the extent of H2 evolution and estimated relative efficiencies of nodules of Austrian winter peas formed by 15 strains of R. leguminosarum. Their rates of H2 evolution in air were about 30% of the rates of H2 evolution under an atmosphere in which N2 was replaced by Ar. Relative efficiency values based on C2H2 reduction rates ranged from 0.55 to 0.80. With some of the strains, hydrogenase activities were demonstrated in intact nodules and in bacteroids, but the levels of activity were insufficient to recycle all the H2 evolved by the nitrogenase system. In both intact nodules and bacteroids the hydrogenase is less sensitive to O2 damage than the nitrogenase system, so H2 uptake capacity was observed in intact nodules by suppressing the nitrogenase-dependent H2 evolution with an atmosphere containing a high O2 concentration, and in bacteroids by using aerobically prepared bacteroid suspensions. The hydrogenase activity of both was dependent on O2 consumption. A K mfor H2 of near 4 μM was determined in suspension of bacteroids from nodules formed by strains 128C53 and 128C56.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 121 (1979), S. 141-145 
    ISSN: 1432-072X
    Schlagwort(e): Azospirillum ; Denitrification ; Nitrogen fixation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The interaction between nitrate respiration and nitrogen fixation inAzospirillum lipoferum andA. brasilense was studied. All strains examined were capable of nitrogen fixation (acetylene reduction) under conditions of severe oxygen limitation in the presence of nitrate. A lag phase of about 1 h was observed for both nitrate reduction and nitrogenase activity corresponding to the period of induction of the dissimilatory nitrate reductase. Nitrogenase activity ceased when nitrate was exhausted suggesting that the reduction of nitrate to nitrite, rather than denitrification (the further reduction of nitrite to gas) is coupled to nitrogen fixation. The addition of nitrate to nitrate reductase negative mutants (nr-) ofAzospirillum did not stimulate nitrogenase activity. Under oxygen-limited conditionsA. brasilense andA. lipoferum were also shown to reduce nitrate to ammonia, which accumulated in the medium. Both species, including strains ofA. brasilense which do not possess a dissimilatory nitrite reductase (nir-) were also capable of reducing nitrous oxide to N2.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 123 (1979), S. 259-265 
    ISSN: 1432-072X
    Schlagwort(e): Nitrogen fixation ; Nitrogenase ; Gene expression ; Protein synthesis ; Regulation ; Klebsiella pneumoniae ; Microbial ecology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract At growth temperatures above 37°C, Klebsiella pneumoniae does not grow in a medium containing N2 or NO 3 - as nitrogen sources. However, both the growth in the presence of other nitrogen sources as well as the in vitro nitrogenase activity are not affected at this temperature. The inability to fix N2 at high temperature is due to the failure of the cells to synthesize nitrogenase and other nitrogen fixation (nif) gene encoded proteins. When cells grown under nitrogen fixing conditions at 30°C were shifted to 39°C, there was a rapid decrease of the rate of de novo biosynthesis of nitrogenase (component 1), nitrogenase reductase (component 2), and the nifJ gene product. There was no degradation of nitrogenase at the elevated temperature since preformed enzyme remained stable over a period of at least 3 h at 39°C. Thus, temperature seems to represent a third control system, besides NH 4 + and O2, governing the expression of nif genes of K. pneumoniae.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 110 (1976), S. 207-213 
    ISSN: 1432-072X
    Schlagwort(e): Nitrogen fixation ; NH 4 + excretion ; Photosynthesis ; Rhodospirillum rubrum ; Photosynthetic bacteria ; Enzymes of ammonia assimilation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract NH 4 + excretion was undetectable in N2-fixing cultures ofRhodospirillum rubrum (S-1) and nitrogenase activity in these cultures was repressed by the addition of 10 mM NH 4 + to the medium. The glutamate analog,l-methionine-dl-sulfoximine (MSX), derepressed N2 fixation even in the presence of 10 mM extracellular NH 4 + . When 10 mg MSX/ml was added to cultures just prior to nitrogenase induction they developed nitrogenase activity (20% of the control activities) and excreted most of their fixed N2 as NH 4 + . Nitrogenase activities and NH 4 + production from fixed N2 were increased considerably when a combined nitrogen source, NH 4 + (〉40 μmoles NH 4 + /mg cell protein in 6 days) orl-glutamate (〉60 μmoles NH 4 + /mg cell protein in 6 days) was added to the cultures together with MSX. Biochemical analysis revealed thatR. rubrum produced glutamine synthetase and glutamate synthase (NADP-dependent) but no detectable NADP-dependent glutamate dehydrogenase. The specific activity of glutamine synthetase was observed to be maximal when nitrogenase activity was also maximal. Nitrogenase and glutamine synthetase activities were repressed by NH 4 + as well as by glutamate. The results demonstrate that utilization of solar energy to photoproduce large quantities of NH 4 + from N2 is possible with photosynthetic bacteria by interfering with their regulatory control of N2 fixation.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1432-072X
    Schlagwort(e): Nitrogen fixation ; Aerobic hydrogen bacteria ; Oxygen sensitivity ; Efficiency ; Aerobic and anaerobic acetylene reduction ; Corynebacterium autotrophicum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The coryneform hydrogen bacterium strain GZ 29, assigned to Corynebacterium autotrophicum fixed molecular nitrogen under autotrophic (H2, CO2) as well as under heterotrophic (sucrose) conditions. Physiological parameters of nitrogen fixation were measured under heterotrophic conditions. The optimal dissolved oxygen concentration for cells grown in a fermenter with N2 was rather low (0.14 mg O2/l) compared with cells grown in the presence of NH 4 + (4.45 mg O2/l). C. autotrophicum GZ 29 had a doubling time of 3.7 h at 30°C with N2 as N-source and sucrose as carbon source and at optimal pO2. Acetylene reduction reached values of 12 nmoles of ethylene produced/minxmg protein. Although the oxygen concentration in the growing culture was kept constant, the optimal dissolved oxygen tension for the acetylene reduction assay shifted to higher pO2-values. The overall efficiency of nitrogen fixation amounted to 22 mg N fixed/g sucrose consumed; it reached a maximal value of 65 mg N fixed/g sucrose consumed at the beginning of the exponential growth phase. Intact cells reduced acetylene even under anaerobic test conditions; further anaerobic metabolic activity could not be ascertained so far.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 107 (1976), S. 25-31 
    ISSN: 1432-072X
    Schlagwort(e): Ferredoxin ; Iron-sulfur proteins ; Nitrogen fixation ; Electron transport to nitrogenase ; Flavodoxin ; Mycobacterium flavum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract 1. Two ferredoxin-type iron-sulfur proteins have been isolated from Mycobacterium flavum 301 grown under nitrogen-fixing, iron-sufficient conditions. No flavodoxin was observed. 2. These ferredoxins are apparently soluble: they were present in the supernatant fraction after disrupting by decompression. Only small amounts were present in particulate fractions. 3. The two ferredoxins were separated by chromatography on DEAE-cellulose, Sephadex or electrophoresis. 4. Both ferredoxins mediated the transfer of electrons from illuminated spinach chloroplasts to a nitrogenase preparation to reduce acetylene. Ferredoxin II was specifically about five times more active than ferredoxin I. Ferredoxin II was also active in the photosynthetic NADP+-reduction whereas ferredoxin I was not. 5. Both ferredoxins were reversibly reduced by either sodium dithionite, illuminated spinach chloroplasts or hydrogen plus hydrogenase from Clostridium pasteurianum. 6. Attempts to determine the primary electron donor for nitrogen fixation in Mycobacterium flavum were unsuccessful. Acetylene reduction in Mycobacterium extracts was obtained only with sodium dithionite or illuminated spinach chloroplasts as electron donors. The reduction of the electron carrier (e. g. ferredoxin) rather than the transfer of electrons from the reduced carrier to nitrogenase was rate-limiting.
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 107 (1976), S. 235-240 
    ISSN: 1432-072X
    Schlagwort(e): Hydrogen bacteria ; Nitrogen fixation ; Acetylene reduction ; Mycobacterium flavum 301 ; Corynebacterium autotrophicum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Seventeen strains of nitrogen-fixing bacteria, isolated from different habitats on hydrogen and carbon dioxide as well as on other substrates, morphologically resembled each other. All strains, including Mycobacterium flavum 301, grew autotrophically with hydrogen. The isolate strain 6 was sensitive to oxygen when dependent on N2 as nitrogen source, a consequence of the sensitivity of its nitrogenase towards oxygen. At the same time, strain 6 was sensitive to hydrogen when growing autotrophically on N2 as nitrogen source, but hydrogen did not affect acetylene reduction by these cells.
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 107 (1976), S. 263-267 
    ISSN: 1432-072X
    Schlagwort(e): Nitrogen fixation ; Root nodule ; Endophyte vesicle ; Alder ; Alnus ; Freeze-etching
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Nitrogen-fixing root nodules of Alnus crispa var. mollis Fern. were studied by transmission electron microscopy and by freeze-etching technique. Ultrathin sectioning of septate vesicles of the actinomycetal endophyte showed an electron transparent zone, the so-called “void area”, between the vesicle cell wall and its encapsulation material. This void area was not observed in the freeze-etching replicas of cryoprotected nodular tissue. It is suggested that the void area is the result of the coming-off of the vesicle cell wall from the capsule and that its formation reflects difficulty in fixing the voluminous mature vesicle of the root nodule endophyte.
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 118 (1978), S. 177-184 
    ISSN: 1432-072X
    Schlagwort(e): Cyanobacteria ; Knallgas reaction ; Hydrogenase ; Hydrogen utilization ; Nitrogenase ; Nitrogen fixation ; Isolated heterocysts ; Anabaena cylindrica ; Nostoc muscorum ; Anabaena variabilis ; Anacystis nidulans ; Cyanophora paradoxa
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Several blue-green algae were surveyed for the occurrence of the hydrogenase which was assayed by the oxyhydrogen or Knallgas reaction in the intact organisms. In aerobically grown cultures, the reaction was detectable in Anabaena cylindrica, Nostoc muscorum and in two Anabaena variabilis species, whereas virtually no activity was observed in Anacystis nidulans and Cyanophora paradoxa. In these latter two algae, the reaction was, however, found after growth under molecular hydrogen for several days, which drastically increased the activity levels with all the algae tested. In the nitrogen fixing species, the activity of the Knallgas reaction was enhanced when all combined nitrogen was omitted from the media. H2 and hydrogenase could not significantly support the CO2-fixation in photoreduction experiments with all blue-green algae investigated here. Hydrogenase was assayed by the dithionite and methyl viologen dependent evolution of hydrogen and was found to be present with essentially the same specific activity levels in preparations of both heterocysts and vegetative cells from Anabaena cylindrica. Na2S2O4 as well as H2 supported the C2H2-reduction of the isolated heterocysts. The H2-dependent C2H2-reduction did not require the presence of oxygen but was strictly light-dependent where H2 served as an electron donor to photosystem I of these cells. It is concluded that hydrogen can be utilized by two different pathways in blue-green algae.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 120 (1979), S. 161-165 
    ISSN: 1432-072X
    Schlagwort(e): Azolla ; Cyanobacteria ; Blue-green algae ; Nitrogen fixation ; Symbiont ; Photoheterotroph ; Algal isolation ; Photosynthesis ; Plant metabolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A procedure has been developed to isolate cyanobacteria from the aquatic fern Azolla. The method is based upon recovery of cyanobacterial “bundles” from digests of plants and use of this material as a massive inoculum for nitrogen-free media, followed by prolonged incubation in light. The procedure appears to select for those cells capable of growth in vitro. Isolated cyanobacteria were found to resemble Anabaena sp. morphologically but were capable of heterotrophic growth and had high nitrogenase activity when grown on fructose in the dark.
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 123 (1979), S. 227-232 
    ISSN: 1432-072X
    Schlagwort(e): Hydrogen production ; Nitrogen fixation ; Photosynthesis ; Cyanobacteria ; Enrichment cultures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Seventy-one cyanobacteria containing cultures were enriched from various soil and water locations either under aerobic and/or anaerobic conditions on agar medium selective for nitrogen fixation. Kept under argon containing 1% CO2 for 24 and 48 h most of these cultures evolved hydrogen at very variable rates up to 116 μl per mg chlorophyll and hour as a mean value over a time period of 24h. Several samples evolved hydrogen more efficiently compared with known hydrogen producing pure strains from culture collections. Thirty-one of the investigated cultures showed a hydrogen formation higher than 10 μl per mg chlorophyll and hour measured over 24 or 48 h. Among these all the morphological forms of cyanobacteria i.e. unicellular and filamentous with or without heterocysts are found. Hence, selecting for nitrogen fixing cyanobacteria seems to be a practical method to find efficient hydrogen producers.
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 123 (1979), S. 37-45 
    ISSN: 1432-072X
    Schlagwort(e): Cyanobacteria ; Blue-green algae ; Hydrogen metabolism ; Nitrogen fixation ; Isolated heterocysts ; Inhibitors ; Plastoquinone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Several natural and artificial electron donors were assayed in the C2H2-reduction of heterocysts isolated from the cyanobacterium Anabaena cylindrica. Among these, molecular hydrogen was the most effective one when the assays were performed in the light. The C2H2-reduction and the Knallgas reaction of intact Anabaena filaments as well as the H2-supported C2H2-reduction of isolated heterocysts were compared for their sensitivity towards several inhibitors known to affect the photosynthetic or respiratory electron flow. Among these, dibromothymoquinone (DBMIB) affected all three reactions equally indicating that plastoquinone is a common intermediate of the H2-consumptions by either the respiratory or the photosynthetic electron transport. Metronidazole inhibited the H2-utilization via photosynthesis but did not affect the consumption of this gas by respiration and therefore allows to differentiate between the two pathways of hydrogen utilization. The studies with the inhibitors are suggestive for a segment of electron carriers on the membranes common to both photosynthesis and respiration in heterocysts of Anabaena.
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 114 (1977), S. 43-49 
    ISSN: 1432-072X
    Schlagwort(e): Cyanobacteria ; Anabaena ; Hydrogenase ; Hydrogen-uptake ; Nitrogenase ; Nitrogen fixation ; Protection mechanism ; Inhibitors
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The blue-green alga Anabaena cylindrica is found to consume molecular hydrogen in a hydrogenase dependent reaction. This hydrogen uptake proceeds in the dark and is strictly dependent on oxygen, thus representing a Knallgas reactions. Its rate is almost as high as that of the endogenous respiration in Anabaena. Studies with inhibitors reveal that hydrogen is utilized via the complete respiratory chain providing additional energy for the alga. CO plus C2H2 completely block the Knallgas reaction which explains the previously reported considerable increase in the total H2 formation representing the difference between the nitrogenase-dependent H2-evolution and the reutilization of the gas catalysed by the hydrogenase in intact Anabaena. H2 is able to support the C2H2-reduction in the dark in a reaction again strictly dependent on oxygen. Moreover, H2 is also consumed in experiments carried out under far red light and in the presence of dichlorophenyl-dimenthyl-urea (DCMU) where the energy for nitrogen fixation is no longer provided by respiration but by cyclic photophosphorylation. Under these conditions, H2 is found to supply electrons for the formation of C2H4 from C2H2 in a reaction no longer dependent on the presence of oxygen. Moreover, in these experiments, the presence of H2 stabilizes the C2H2-reduction activity against the deleterious effect of oxygen. Thus, this communication provides evidence for a triplicate function of the H2-uptake catalysed by hydrogenase in intact Anabaena which is (a) to provide energy by the Knallgas reaction, (b) to supply reducing equivalents for nitrogenase, (c) to protect nitrogenase from damage by oxygen.
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 111 (1976), S. 195-196 
    ISSN: 1432-072X
    Schlagwort(e): Mutation ; Blue-green alga ; Anabaenopsis raciborskii ; Gas vacuole ; Nitrogen fixation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract From a bloom forming blue-green alga, Anabaenopsis raciborskii, spontaneous mutants, which had lost the ability to form gas vacuoles have been isolated; the mutant frequency was 4.8×10-3. The filaments of gas vacuole-less mutants settled at the bottom of flasks in liquid culture media unlike the parent alga. The growth and nitrogen fixation were comparatively poor in the mutants.
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 121 (1979), S. 155-159 
    ISSN: 1432-072X
    Schlagwort(e): Blue-green algae ; Nitrogen fixation ; Anabaena ; Cyanobacteria ; Marine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Five strains of heterocystous blue-green algae capable of high rates of growth and nitrogenase activity were isolated from shallow coastal environments. Growth of the organisms was characterized with respect to temperature, NaCl concentration in the medium, and nitrogen source. The temperature optima ranged from 35–42°C, and all but one of the strains displayed a requirement for added NaCl. The generation times under N2-fixing conditions were 5.1–5.9 h, and were as low as 3.4 h for growth on NH4Cl. Nitrogenase activity (C2H2 reduction) was high throughout the logarithmic growth phase of each strain. The maximum value observed for one strain was 65.5 nmoles C2H4 produced/mg protein x min, and the average values for the five strains ranged from 24.5–46.7 nmoles C2H4/mg protein x min. The organisms all belong to the genusAnabaena. The growth and nitrogenase activity of these strains are much higher than those of the heterocystous blue-green algae commonly used for investigation of nitrogen metabolism, and they thus should prove to be useful physiological tools. Their prevalence, as judged by the ease of their enrichment and isolation, in bay and estuarine environments suggests that they are important contributors of combined nitrogen.
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 101 (1979), S. 143-163 
    ISSN: 1615-6102
    Schlagwort(e): Azospirillum ; Nitrogen fixation ; Sugarcane ; Tissue culture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Tissue cultures of sugarcane support abundant growth ofAzospirillum brasilense (SP 7). Visible after 1–2 weeks as a white or pink slime, this growth reaches 2×108 bacteria/mm2 on the surface of callus. Growth of the bacterium is strictly extracellular in viable callus, and instances of intracellular growth result from rupture of the cell wall during senescence of callus tissue. A significant proportion of the bacterial population on callus is pleomorphic. Varying the nitrogen source in the nutrient medium caused no obvious effect on callus cell structure. The presence of the bacterium caused structural alterations in callus cells which did not inhibit overall growth of the bacterium. Growth of callus as tight groups of cells lacking intercellular spaces may be important for the establishment of a long-term association withAzospirillum. The interface of bacteria and live callus tissue is at the surface of tight cell groups. Browning of the surface cell layers of these groups in the presence ofAzospirillum is not of the rapid nature known for hypersensitivity reactions. Rather, this production of phenolics appears to be due to the accumulation of extracellular bacterial metabolites. The ultrastructure of this and other callus reactions is described. As evidenced by organogenesis, the associated cultures have remained viable for at least 18–20 months.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 51 (1979), S. 187-196 
    ISSN: 1573-5036
    Schlagwort(e): Acetylene reduction ; Aerobic ; Anaerobic ; Bacillus ; Nitrogen fixation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Among 390 isolates from Egytiian soils initially grown on Brown's N-free agar, 15 facultative Bacillus isolates were able to reduce acetylene in Stanier's N-poor broth under both aerobic and anaerobic (N2 atmosphere) conditions. Some of these isolates were Gram-positive, with unswollen sporangia and thin-walled endospores. Other strains were with slightly or definitely bulged sporangia. Yeast extract (0.01%) was essential for growth stimulation and N2[C2H2] fixation by these isolates. Replacing yeast extract with 20 μg/ml (NH4)2SO4 or biotin, thiamine and amino acids (singly or in combination) resulted in stimulation of growth and N2[C2H2] fixation, though at lower rates than in yeast extract. One isolate was able to grow and reduce C2H2 in Stanier's N-free liquid medium. Nitrogenase [C2H2] activity of the anaerobically grown and incubated cultures was greater than aerobic cultures. Addition of 0.1% CaCO3 to the culture media significantly increased and O2 partially inhibited, N2[C2H2] fixation by these Bacillus isolates. Studies of the characteristics and N2[C2H2] fixing activities of these isolates indicate that at least some of them are new nitrogen-fixingBacillus species.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 51 (1979), S. 355-361 
    ISSN: 1573-5036
    Schlagwort(e): Aldicarb ; 14C-carbon metabolism ; Cowpea ; Growth ; Nitrogen fixation ; Nodulation ; Pesticide ; Respiration ; Rhizobium ; Soil ; Symbiosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Addition of aldicarb (2 methyl-2(methyl thio) propionaldehyde-0-methyl carbamoyl oxime) in the growth medium enhanced the growth ofRhizobium sp. (cowpea group) at 2 ppm level while an inhibition was observed at the normal (5 ppm) and higher (10 ppm) concentrations. Respiration of the cells was also inhibited by 5 and 10 ppm levels of the chemical eventhough a stimulation was observed at 2 ppm (lower) concentration. The insecticide, when incorporated at 5 and 10 ppm levels in the medium increased the14C-glucose incorporation and considerably altered the assimilation of the radioactive carbon in different fractions of rhizobium cells. Soil application of this insecticide (Temik 10 G) reduced the number of nodules formed and the total nitrogen content in cowpea plants inoculated with theRhizobium sp. but enhanced the dry matter production of cowpea plants.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 52 (1979), S. 49-57 
    ISSN: 1573-5036
    Schlagwort(e): Acetylene reduction ; Azospirillum ; Dry weight ; Greenhouse ; Inoculation ; Millet ; Nitrogen fixation ; Pennisetum ; Spirillum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Millet plants (Pennisetum glaucum) were grown at three levels of nitrogen fertilization with and without an inoculum of live nitrogen-fixing Azospirillum cells. The highest average rate of nitrogen fixation as estimated from acetylene reduction by excised preincubated roots was only 23g N2 fixed per ha per day and occurred after treatment with low levels of nitrogen amendment. The average rates of acetylene reduction for intact plants at all treatments were also low. The lack of significant nitrogen fixation due to an Azospirillum-millet association in this study was substantiated by plant dry weight analysis, and determination of the nitrogen content of plants, pot leachate, and soil. There was significant correlation between the total nitrogen content of the plants per pot at the termination of the experiment and the amount of nitrogen fertilizer added initially, but there was no effect of inoculum on final total nitrogen content.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 53 (1979), S. 319-328 
    ISSN: 1573-5036
    Schlagwort(e): Dolichos ; Growth ; Greenhouse ; Lablab ; Leaf area ; Nitrogen fixation ; Nodulation ; Sand culture ; Sugars ; Sulfur
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary In order to explore interrelations between S nutrition, soluble sugars, leaf area, nodulation and N2 fixation, greenhouse experiments were done with several levels of S added to perlite-sand cultures or to a moderately S-deficient soil. Sulfur had indirect effects on nodulation and N2 fixation, possibly by improving sugars supply and N metabolism. In perlite-sand culture, leaf area increased with concentrations of supplied S up to 50 and 200 μM for symbiotic and N-treated plants respectively, then decreased at higher concentrations. Plant yield and total sugars content (mg per plant) for the N-treated plants behaved similar to leaf area in response to added S but in the symbiotic plants maximum values were obtained at 100 μM S. In soil, Mo had no effect on growth but interacted significantly with S in affecting total sugars content. High levels of S depressed sugars content at low Mo but raised it at high Mo. Sulfur increased the N content of soil-grown plants. It increased the N content of plants grown in perlite-sand culture except at very high levels of S. There was little effect on concentration of N in the shoots. Nitrogen content correlated significantly with leaf area and sugar content, and highly significantly with S concentration in the shoots.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Hydrobiologia 49 (1976), S. 53-57 
    ISSN: 1573-5117
    Schlagwort(e): Nitrogen fixation ; Acetylene reduction ; Lake Mendota
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The contribution of nitrogen fixation to the nitrogen budget of Lake Mendota has been calculated. On average, the equivalent of 1.28 × 105 kg of NH3 (as determined by the acetylene reduction technique) was added to this eutrophic lake during June, July and August. Diurnal variation (approximately two-thirds of the day's fixation occurs prior to noon) in algal nitrogen fixation, and variation of fixation with depth (3.6% of the fixation in the column occurs in the top decimeter) were characterized as prerequisites to this calculation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 51 (1979), S. 163-165 
    ISSN: 1573-5036
    Schlagwort(e): Acetylene reduction ; Actinomycete symbioses ; Datisca cannabina ; Nitrogen fixation ; Root nodules
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The occurrence of root nodules inDatisca cannabina is reported. The nodules are typically of the Alnus type, forming dichotomously-branched coralloid clusters. The enlarged cortical cells contain vesicle clusters of the endophyte. The nodules reduced acetylene to ethylene at a rate of 5.5 μmoles ethylene per g fresh wt of nodules per hour.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 28
    ISSN: 1573-5036
    Schlagwort(e): Arachis hypogaea ; Peanuts ; Rhizobium ; Nitrogen fixation ; Nitrogen fertilizers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The potential of peanuts for symbiotic nitrogen fixation is considerable and under optimal edaphic and climatic conditions it reached 222 kg N2/ha, which was 58% of the nitrogen accumulated in the plants. The effect of the Rhizobium inoculation on crude protein accumulation in the yield (kg/ha) was 3–4 times greater than its effect on the yield of pods and hay. There was an inverse relationship between the protein and oil content in the kernels. Seasonal changes in nitrogenase activity in the nodules were determined by the acetylene reduction method during two growing seasons. Under favorable conditions the specific activity of the nitrogenase reached a very high level (up to 975 μmoles C2H2 g dry wt nod/h) and the total activity (μmoles C2H4/plant/h) was also high in spite of the relatively poor nodulation (weight and number). The high activity was drastically reduced (to 75 μmoles C2H4 g dry wt nod/h) due to exceptionally hot and dry weather, which occurred in the middle of the second half of the growing season. It appears that N2-fixation (nitrogenase activity) is more sensitive to these unfavorable conditions, than is nodule growth. Maximum nitrogenase activity was observed during the podfilling stage; until 50–60 days after planting, nitrogenase activity was very low.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 29
    ISSN: 1573-5036
    Schlagwort(e): acetylene reduction assay ; Nitrogen fixation ; 15N natural abundance ; Soybean
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The use of variations in natural abundance of15N between nitrogen fixing and non nitrogen fixing soybeans was investigated for quantitative estimate of symbiotic nitrogen fixation. Isotopic analysis of 4 varieties of inoculated and non-inoculated soybeans growing under field conditions, with and without N-fertilizer was determined. It was found that inoculated soybeans had a significantly lower15N content than non-inoculated ones. Estimates of the participation of fixed N to the total nitrogen content of inoculated soybeans were calculated from these differences. They were compared to estimates calculated from differences in N yield between inoculated and noninoculated plants and to the nitrogenase activity, measured by the C2H2 reduction assay over the growing season. Estimates given by the15N measurements were correlated with the C2H2 reducing activity but not with the differences in the N yield. This shows that the isotopic composition was dependent on the amount of fixed nitrogen and consequently that the estimates of fixed nitrogen based on natural15N abundance should be reliable. The absence of correlation between estimates based on15N content and estimates based on N yield was explained by differences in the uptake of soil nitrogen between inoculated and non inoculated soybeans.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 52 (1979), S. 571-578 
    ISSN: 1573-5036
    Schlagwort(e): Acetylene reduction ; Actinomycetous symbiosis ; Alnus glutinosa ; Hydrogenase Hydrogen evolution ; Hydrogen uptake ; Nitrogen fixation ; Respiration ; Root nodules
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary In the growing season no net H2 evolution is detected when root nodules ofAlnus glutinosa are incubated in air or in argon containing 20% O2. Due to the hydrogenase activity, N2-fixing root nodules consume added H2 at a rate of about 1.4 μmoles H2.g fresh nodule−1.h−1. The uptake of H2 is only found in summer. At the end of the season, in autumn, nodules evolve significant quantities of H2 although the nodules still continue to fix nitrogen. In-vitro studies with fractionated homogenates of summer-harvested nodules show that the recovery of the hydrogenase is high when using methylene-blue or phenazine metasulfate as electron acceptors. No hydrogenase activity is detected in homogenates of autumn-harvested nodules. The hydrogenase is localised in the microsymbiont.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 53 (1979), S. 541-545 
    ISSN: 1573-5036
    Schlagwort(e): Acetylene reduction ; Root nodules ; Actinomycetous symbiosis ; Rubus ellipticus ; Raspberry ; Rosaceae ; Food-yielding nodulated non-legume ; Nitrogen fixation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Nitrogenase activity as assayed by acetylene reduction was observed in detachedRubus ellipticus J. E. Smith root nodules collected in the field and tested under ambient conditions. The nitrogenase activity was 8.4 μmoles C2H4.gfr. wt nodule−1.h−1 or 24.0 μmoles C2H4.g dry wt nodule−1.h−1 being at a rate comparable with that measured in some other non-legumes assayed in Java at the same time under similar conditions. Nodule morphology bore little resemblance to the root nodules of other non-leguminous plants and nodule structure was different from the other rosaceous examples. The endophyte inhabiting the root nodules was actinomycetal.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Hydrobiologia 56 (1977), S. 273-279 
    ISSN: 1573-5117
    Schlagwort(e): Nitrogen fixation ; nutrient enrichment ; limnocorral
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Nitrogen fixation was measured in situ by the 15N tracer technique in the Bay of Quinte, Lake Ontario, and three lake enclosures with different nutrient enrichment. The fixation rates in the Bay were low but detectable during the summer season. The fixation activities were found to be correlated with the presence of nitrogen-fixing blue-green algae and the distribution of the algal species in the water was affected by nitrate enrichment. The study showed that, with the addition of nitrate, species not able to fix atmospheric nitrogen became predominant. However, in the absence of external nitrogen (i.e., nitrate), species able to fix nitrogen became dominant. Phosphorus enrichment alone did result in higher N-fixation rates in the water and, without the addition of phosphorus, the fixation rates are lower and fluctuate throughout the season, presumably dependent on the availability of phosphorus in the water. A comparison between the 15N-isotopic method and the acetylene reduction method is reported and the factors involved in the variations between these two methods are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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