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  • 1
    Electronic Resource
    Electronic Resource
    Inorganic nitrogen metabolism in marine bacteria: Nitrate uptake and reduction in a marine pseudomonad (1975)
    Springer
    Marine biology 31 (1975), S. 7-13 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth experiments in batch cultures indicated that the uptake of nitrate by the marine pseudomonad PL1 was inhibited in the presence of ammonia provided that the ammonia concentration was higher than 1 mM. At ammonia concentrations of less than about 1 mM, however, both nitrate and ammonia were utilised simultaneously. The saturation constants for nitrate and ammonia uptake were both 2.6x10-4 M, and similar to the Michaelis constants of nitrate reductase for nitrate (2.9x10-4 M) and glutamine synthetase for ammonia (2x10-4 M). Nitrate reductase activity linked to NADH was detected in chemostat-grown cultures with nitrate as nitrogen source, and in cultures containing limiting concentrations of nitrate and ammonia, ammonia or glutamate. Enzyme synthesis appeared to be repressed in cultures containing an excess of ammonia or glutamate. Chemostat cultures utilised ammonia or glutamate in preference to nitrate, while there was no marked preference between ammonia and glutamate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390642
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Inorganic nitrogen metabolism in marine bacteria: The intracellular free amino acid pools of a marine pseudomonad (1976)
    Springer
    Marine biology 38 (1976), S. 101-109 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The marine pseudomonad bacterium PL1 contains an intracellular pool of free amino acids which consist mainly of glutamate with small amounts of glutamine and aspartate when grown in a nutrient medium containing 0.2 M NaCl. When the NaCl concentration of the growth medium is increased to 0.8 M, proline becomes a major component of the intracellular pool together with glutamate—at this molarity and under suitable nutrient conditions these amino acids comprise 20% of total bacterial amino acid nitrogen. When grown in a nutrient growth medium containing a constant level of NaCl, the intracellular pool size can vary by a factor of 4 depending on the concentration of carbon and nitrogen in the medium. Experiments show that the amino acid pool can act as a nitrogen reserve but has little function as a carbon reserve. At high NaCl concentrations there is a marked dependence for growth on the presence of sufficient potassium in the medium. However, no correlation between K+ and glutamate concentration in either nitrogen or K+-limited cultures has been found. None of the enzymes associated with glutamate biosynthesis was influenced by NaCl levels between 0.2 and 0.5 M. Neither Na+ or K+ stimulated the activity of these enzymes when tested in vitro.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390763
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  • 3
    Electronic Resource
    Electronic Resource
    Some biologically important low molecular weight organic acids in the sediments of Loch Eil (1979)
    Springer
    Marine biology 50 (1979), S. 375-383 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The isolation of biologically important low molecular weight organic acids from organically enriched sediments in Loch Eil, Scotland, was carried out by extraction of pore water with acidified ethyl acetate. High concentrations of acetic acid, up to 1.8 mg g-1 dry weight of sediment were found at Station E-24. Propionate, butyrate, valerate, lactate and traces of succinate were also found. Succinate was present in significant amounts, 42.2 μg g-1 dry weight of sediment at Station E-70, which received a higher input of organic matter than E-24. Both propionate and succinate were absent from a control station in the Lynn of Lorne where the sediment was low in carbon compared with Loch Eil. In experimental tanks, acetate levels increased as the input of organic carbon (as cellulose) was increased up to a load level of 1.5 g m-2 day-1. Above this, acetate decreased and succinate appeared. Succinate was not detected in low-loaded tanks. Experiments with sieved mud showed a vertical distribution of the different acids with depth. Lactate and succinate reached highest concentration in the 0 to 3 cm layer, acetate at 3 to 6 cm and propionate at 6 to 9 cm. The results are discussed in relation to the role of these acids as food sources and as indicators of biochemical pathways taking place in sediments with different carbon input levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387015
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Comparative measurement of the redox potential of marine sediments as a rapid means of assessing the effect of organic pollution (1979)
    Springer
    Marine biology 53 (1979), S. 371-379 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A rapid method for measuring the redox potential (Eh) values of marine sediments is described. This method has been used to relate changes in the areas of highly reduced sediment in a sea loch system to the continuously fluctuating inputs of organic waste from a pulp and paper mill. Subsequent faunal changes in these areas can be related to changes in the measured sedimentary redox level. The method is suggested as a rapid means of assessing the potential impact of an additional organic input to a marine sediment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391620
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  • 5
    Electronic Resource
    Electronic Resource
    Nitrogenase activity, amino acid pool patterns and amination in blue-green algae (1972)
    Springer
    Planta 108 (1972), S. 133-145 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The free amino acid pools in the nitrogen-fixing blue-green algae Anabaena cylindrica, A. flos-aquae and Westiellopsis prolifica contain a variety of amino acids with aspartic acid, glutamic acid and the amide glutamine being present in much higher concentrations than the others. This pattern is characteristic of that found in organisms having glutamine synthetage/glutamate synthetase [glutamine amide-2-oxoglutarate amino transferase (oxido-reductase)] as an important pathway of ammonia incorporation. Under nitrogen-starved conditions the level of acetylene reduction (nitrogen fixation) and the glutamine pool both increase but the free ammonia pool decreases, suggesting that ammonia rather than glutamine regulates nitrogen fixation. Glutamine synthetase has been demonstrated in Anabaena cylindrica using the γ-glutamyl transferase assay and also using a biosynthetic assay in which Pi release from ATP during glutamine synthesis was measured. The enzyme (γ-glutamyl transferase assay) is present in nitrogen-fixing cultures and activity is higher in aerobic than in microaerophilic cultures. Ammonium-grown cultures have lowest levels of all and activity in the presence of nitrate-nitrogen (150 mg nitrogen 1-1) is lower than in aerobic cultures growing on elemental nitrogen. Ammonium-nitrogen and nitrate-nitrogen have no effect on glutamine synthetase in vitro. Glutamate synthetase also operates in nitrogen-fixing cultures of Anabaena cylindrica.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386075
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    Paper (German National Licenses)
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