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  • Continuous culture  (90)
  • Regulation  (84)
  • 1
    ISSN: 1432-072X
    Keywords: Candida utilis ; Potassium-limitation ; Continuous culture ; Oxidative phosphorylation ; Yield values
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When grown in a defined simple salts medium, plus vitamins, Candida utilis displayed an absolute requirement for potassium. But the potassium content of this yeast was exceedingly variable and, with aerobic chemostat cultures (grown at a dilution rate of 0.1 h-1; 30° C; pH 5.5), was low (〈 0.2%, w/w) when they were potassium-limited and high (〉 2%, w/2) when glucose-limited. With potassium-limited cultures, the cell-bound potassium content also varied markedly with growth rate, though hardly at all with glucose-limited cultures; magnesium- and phosphate-limited cultures gave intermediate responses. Changes in cell-bound potassium content correlated only weakly with changes in the cellular contents of magnesium, phosphate and RNA, but strongly with changes in both the Y glucose and Y O values, indicating an involvement of potassium in the generation of energy by oxidative phosphorylation reactions and/or the utilization of this energy for growth processes. Studies with isolated mitochondria revealed that potassium-limited organisms had a changed content of cytochrome b relative to cytochrome a, and lacked coupling at either site 2 or site 3 of the respiratory chain. These results are discussed in relation to the reported functions of potassium in the growth of micro-organisms, and the organizational differences between prokaryotic and eukaryotic cells.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 112 (1977), S. 283-285 
    ISSN: 1432-072X
    Keywords: Wine yeasts ; Sulfur metabolism ; Regulation ; Sulfate uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Five different strains of wine yeasts were investigated with respect to active uptake of [35S] sulfate and its regulation by methionine. Considerable differences exist between “low” and “high” sulfite-producing strains in the initial velocity of sulfate uptake. Further differences were established in repression of sulfate permease by l-methionine, most evident in a total lack of repression in one of the “high” sulfite producers. These findings explain in part variable sulfite and sulfide formation.
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  • 3
    ISSN: 1432-072X
    Keywords: cAMP ; Regulation ; Chlorophyll synthesis ; Chlorella fusca
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The intracellular concentration of cAMP in the green alga Chlorella fusca was in the range of 2 · 10-9 to 10-8 moles/g dry weight and was strongly dependent on the growth conditions. The cAMP level was high with high light intensity, low nitrate or glucose concentration. Intracellular cAMP increased only by factor of 2 when high amounts (up to 10-3 M) of cAMP were added to the medium. Most of the given cAMP was converted to 5′-AMP. Addition of cAMP had little effect on the chlorophyll content of the cells, only at 10-6 M some enhancement in photoautotrophic cultures was observed. On the other hand high amounts of cAMP in the medium increased the growth rate. DBcAMP* showed a positive effect on chlorophyll synthesis and growth rate at much lower concentrations compared to cAMP. Stimulation effects of exogenous cAMP on the synthesis of chlorophyll were also observed in mixotrophic cultures with a high glucose/nitrate ratio, conditions where chlorophyll synthesis is repressed. Similar to autotrophic conditions DBcAMP was more effective than cAMP. These data indicate that cAMP may act in a system controlling the chlorophyll content of the cells in response to nutrients or light.
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  • 4
    ISSN: 1432-072X
    Keywords: Candida utilis ; Continuous culture ; Acetate ; Culture pH value ; Respiratory efficiency ; Growth inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Candida utilis was grown on acetate in chemostat cultures that were, successively, carbon and ammonia-limited (30° C; pH 5.5). With carbon(acetate)-limited cultures, the specific rate of oxygen consumption (q O 2) was not a linear function of the growth rate but was markedly stimulated at the higher dilution rates, thus effecting a marked decrease in the Y O value. This increased respiration rate, and decreased yield value, correlated closely with a marked increase in the extracellular acetate concentration. Under ammonia-limiting conditions, very low Y O values were found, generally comparable with those found with carbon-limited cultures growing at the higher dilution rates, but these varied markedly with the extracellular acetate concentration. Thus, when the unused acetate concentration was raised progressively from about 5 g/l to about 21 g/l, the Y O value decreased non-linearly from 11.4 to 5.8. When the extracellular acetate concentration was further increased to 25 g/l, growth was inhibited and the culture washed out. This relationship between respiration rate and the extracellular concentration of unused acetate was also markedly influenced by the culture pH value. Thus, with a fixed extracellular acetate concentration (16±2g/l) and dilution rate (0.14 h−1), lowering the culture pH value progressively from 6.9 to 5.1 effected a marked and progressive increase in the respiration rate. Further lowering of the culture pH to 4.8, however, caused a complete collapse of respiration. In contrast to this situation, progressively lowering the pH value of an acetatelimited culture from 6.9 to 4.5 affected only slightly the culture respiration rate, and growth was possible even at a pH value of 2.5. These results are discussed in the context of the possible mechanisms whereby acetate exerts its toxic effect on the growth of C. utilis.
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  • 5
    ISSN: 1432-072X
    Keywords: Root nodule symbiosis ; Rhizobium meliloti ; Medicago sativa ; Nitrogenase activity ; Regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Symbiotic nitrogen fixation of Rhizobium meliloti bacteroids in Medicago sativa root nodules was suppressed by several inorganic nitrogen sources. Amino acids like glutamine, glutamic acid and aspartic acid, which can serve as sole nitrogen sources for the unnodulated plant did not influence nitrogenase activity of effective nodules, even at high concentrations. Ammonia and nitrate suppressed symbiotic nitrogen fixation in vivo only at concentrations much higher than those needed for suppression of nitrogenase activity in free living nitrogen fixing bacteria. The kinetics of suppression were slow compared with that of free living nitrogen fixing bacteria. On the other hand, nitrite, which acts as a direct inhibitor of nitrogenase, suppressed very quickly and at low concentrations. Glutamic acid and glutamine enhanced the effect of ammonia dramatically, while the suppression by nitrate was enhanced only slightly.
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  • 6
    ISSN: 1432-072X
    Keywords: Escherichia coli ; Continuous culture ; Fumarate reduction ; Maximal growth yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Escherichia coli was grown anaerobically on sodium fumarate and molecular hydrogen or sodium formate in continuous culture. The maximal growth yield and the maintenance coefficient were determined. In a mineral medium a Y fum max value of 6.6 g dry weight per mol fumarate was found. This value increased to 7.5 when casamino acids were present in the medium. From these data and the corresponding Y ATP max values it could be calculated that per mol of fumarate reduced, 0.4 mol of ATP became available for growth. In batch culture a Yfum value of 4.8 g dry weight per mol fumarate was determined.
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  • 7
    ISSN: 1432-072X
    Keywords: Physarum polycephalum ; Amoebae ; Aminopeptidases ; Acid proteases ; Regulation ; Development ; Differential gene activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cultivation of Physarum polycephalum amoebae in two media with different protein contents revealed a regulation of aminopeptidases and proteases depending on the albumin content of the medium: in growing amoebae and plasmodia the aminopeptidases have similar isoenzyme patterns and relative activities against nitroanilides. One alanine and four leucine aminopeptidase isoenzymes were found within the slightly acid pH range. During growth amoebae secrete—different from plasmodia—leucine aminopeptidase into the medium with low protein content. In an albumin-rich medium additional alanine aminopeptidase activity was found. Out of nine plasmodial proteases four were found in amoebae too. Only one band (pI 3.6) was present in the protein-poor medium. No protease activity could be detected in the proteinrich medium.
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  • 8
    ISSN: 1432-072X
    Keywords: Streptococcus cremoris ; Cell wall proteinase ; Calcium dependency ; Regulation ; Translational control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The persistent accumulation of proteinase (PIII) activity in the cell wall of Streptococcus cremoris strain AM1 during growth depends on the presence of Ca2+-ions in the medium. In the absence of calcium initial accumulation of activity in the cell wall is observed, followed by a decrease to a low final level. Under this condition no increase of proteolytic activity is found in the extracellular fluid. A possible function of calcium in the stabilization of the enzyme is discussed. Prolonged accumulation of catalytically active proteinase PIII in the cell wall occurs in the absence of messenger ribonucleic acid synthesis. This process involves de novo protein synthesis supported by preformed proteinase-specific messenger ribonucleic acid, which is possibly either intrinsically long-lived or is stabilized following its transcription. The level of the extracellular concentration of amino acids and/or peptides regulates the translation of newly synthesized proteinase-specific messenger ribonucleic acid and, possibly, the growth of the organism in milk.
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  • 9
    ISSN: 1432-072X
    Keywords: Growth yield ; Thiobacillus ; Maintenance ; Chemolithotroph ; Thiosulfate ; Formate ; Energy limitation ; Continuous culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Molar growth yield studies on chemostat cultures of Thiobacillus neapolitanus grown in thiosulfate-minerals medium have confirmed earlier observations that the dry weight increased linearly with the dilution rate. The observed increase can be explained neither by a change in cell composition nor by the observed excretion of organic compounds. The increase of the molar growth yield over the full range of growth rates, that is also observed in other obligate chemolithotrophs, was not found in the facultatively chemolithotrophic Thiobacillus A2, grown on thiosulfate or formate. The interpretation of the results in terms of “maintenance energy requirement” is discussed. It is concluded that these results do not allow a mathematical treatment according to the empirical formula of Pirt.
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  • 10
    ISSN: 1432-072X
    Keywords: Thiobacillus neapolitanus CO2 fixation, excretion products ; Glycolate ; Ribulose bisphosphate carboxylase/oxygenase ; Chemolithotrophs ; Continuous culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Thiobacillus neapolitanus grown in minerals medium in a thiosulfate-limited chemostat excreted 15% of all the carbon dioxide fixed as 14C-organic compounds at a dilution rate (D) of 0.03 h-1. At D=0.36 h-1 this excretion was 8.5%. Up to a D of 0.2h-1 glycolate was the major excretion product. Glycolate excretion was maximal at a pO2 of 100% air saturation (a.s.) and not detectable at a pO2 of 5% (a.s.). Increasing the pCO2 of the gassing mixture to 5% (v/v), at a pO2 of 50% a.s. resulted in a lowering of the glycolate excretion from 3.5% of the total CO2 fixed to 1.8%. These results indicate that glycolate excretion in T. neapolitanus is due to oxygenase activity of D-ribulose-1,5-bisphosphate carboxylase. HPMS (2-pyridylhydroxymethanesulfonate), an inhibitor of glycolate metabolism, did not stimulate the glycolate production in T. neapolitanus. Glycolate excretion was not observed in thiosulfate-limited chemostat cultures of the obligately chemolithotrophic Thiomicrospira pelophila or in thiosulfate- or formate-grown cultures of the facultatively chemolithotrophic Thiobacillus A2.
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