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  • Regulation  (84)
  • Photosynthesis  (69)
  • 1
    ISSN: 1432-072X
    Keywords: Biliproteins ; Phycoerythrocyanin ; Assembly forms ; Anabaena sp. ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies are presented of the biliproteins of Anabaena sp. This filamentous cyanobacterium contains three major biliproteins. Whereas two of these, C-phycocyanin and allophycocyanin, are common to all cyanobacteria, the third, phycoerythrocyanin (λmax∼568nm) has hitherto not been described and its distribution among cyanobacteria appears to be limited. Anabaena variabilis and Anabaena sp. 6411 allophycocyanin, C-phycocyanin, and phycoerythrocyanin were purified to homogeneity and characterized with respect to molecular weight, isoelectric point, absorption spectrum and amino acid composition. The α and β subunits of each of these proteins were also purified to homogeneity and characterized in the same manner. The tetrapyrrole chromophore content was determined for each of the proteins and subunits. The α subunit of phycoerythrocyanin carries a novel phycobiliviolin-like chromophore. This chromophore has not previously been detected in cyanobacterial biliproteins, but has been noted as a prosthetic group of a cryptophytan phycocyanin. Sedimentation equilibrium studies show that at pH 7.0, at protein concentrations of 0.2–0.6 mg/ml, allophycocyanin, C-phycocyanin and phycoerythrocyanin, each exists as a trimeric aggregate, (αβ)3, of molecular weight of approximately 105000. Structural studies of microcrystals of these three biliproteins by electron microscopy and X-ray diffraction reveal a common plan for the construction of higher assembly forms. The major building block appears to be the trimer (αβ)3. It is proposed that this is a dise-like structure about 3.0×12.0 nm. The individual α or β subunits are roughly spherical, 3 nm in diameter. Allophycocyanin trimers stack to form bundles of rods which form long needles. Both phycocyanin and phycoerythrocyanin form double dises (αβ)6 which are visible as ring-shaped structures by electron microscopy. The mode of assembly of the biliproteinstructures in the phycobilisome is, as yet, unknown.
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  • 2
    ISSN: 1432-072X
    Keywords: Cyanophage ; Blue-green algae ; Blue-green algal virus ; AS-1 ; Anacystis nidulans ; Phage development ; Photosynthesis ; Synechococcus 6301
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The development cycle of the cyanophage AS-1 was studied in the host blue-green alga, Anacystis nidulans, under conditions that impair photosynthesis and under various light/dark regimes. Under standard conditions of incubation the 16-h development cycle consisted of a 5-h eclipse period and an 8-h latent period. Burst size was decreased by dark incubation to 2% of that observed in the light. An inhibitor of photosystem II, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), reduced the burst size to 27% of that of the uninhibited control, whereas cyanophage production was completely abolished by carbonyl-cyanide m-chlorophenyl hydrazone (CCCP), an inhibitor of photosynthetic electron transport. Dark incubation of infected cells decreased the latent period by 1–2 h and the eclipse period by 1 h, once the cultures were illuminated. This suggests that adsorption took place in the dark. Intracellular growth curves indicated that light is necessary for viral development. Infected cells must be illuminated at least 13 h to produce a complete burst at the same rate as the continuously illuminated control. Low light intensities retarded the development cycle, and at lowest light intensities no phage yield was obtained. AS-1 is highly dependent on host cell photophosphorylation for its development.
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  • 3
    ISSN: 1432-072X
    Keywords: Blue-green algae ; Gas vesicles ; Gas vacuoles ; Pseudovacuoles ; Growth ; Photosynthesis ; Oxygen evolution ; Pigments ; Light shielding ; Volume regulation ; Free space
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Physiological evidence was obtained for a light shielding role for gas vacuoles inMicrocystis aeruginosa Kuetz. emend. Elenkin, by comparing photosynthetic oxygen evolution, growth behaviour and pigment composition of cells with intact or collapsed gas vacuoles. The oxygen evolution rates were strongly dependent on cell concentration, a maximum rate for cells with intact gas vacuoles occurring at about 1.4×109 cells/ml and for cells with collapsed gas vacuoles at about 2.5×109 cells/ml. By using light saturation curves for oxygen evolution, it was estimated that at low light intensities up to 30% of the photosynthetically useable light was shielded at a cell concentration of 6×108 cells/ml. Collapsing the gas vacuoles twice daily did not alter the initial growth rate of the cultures, but enabled them to reach a higher final cell density. Collapsing of gas vacuoles during growth for about four generations resulted in a lower level of all acetone soluble pigments with a greater relative reduction in carotenoids than in chlorophyll a. Collapse of the gas vacuoles does not alter the cell volume. Various optical interactions which could account for light shielding are discussed.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 110 (1976), S. 207-213 
    ISSN: 1432-072X
    Keywords: Nitrogen fixation ; NH 4 + excretion ; Photosynthesis ; Rhodospirillum rubrum ; Photosynthetic bacteria ; Enzymes of ammonia assimilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    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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  • 10
    ISSN: 1432-072X
    Keywords: Photokinesis ; Red algae ; Porphyridium cruentum ; Action spectrum ; Photosynthesis ; Inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photokinesis of the red alga Porphyridium cruentum was studied with the aid of a population method. Because of the slow spreading velocity (0.35 μm/min) the duration of the experiments was 7 days in general. According to the white light illuminance-response curve the zero threshold of photokinesis lies below 10 lx and the optimum around 10,000 lx. With further increasing illuminance the photokinetic effect decreases, reaching zero at about 100,000 lx. The action spectrum indicates that the photokinetically active radiation is absorbed by photosynthetic pigments, namely the biliproteins B-phycoerythrin, R-phycocyanin and allo-phycocyanin, as well as by chlorophyl a, although the photokinetic effect of blue light is relatively low. From the action spectrum and the results of inhibitor experiments with DCMU, DBMIB and DSPD it is concluded that the photokinetic effect is due to an additional ATP supply from non-cyclic and/or pseudo-cyclic photophosphorylation to the motor apparatus.
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