Dependence of H+ exchange and oxygen evolution on K+ in the marine cyanobacterium Synechococcus sp. strain UTEX 2380

Light-induced net H+ efflux, photosynthetic oxygen evolution, and medium alkalization during the steady state of photosynthesis were specifically stimulated by K+ from pH 6 through 8.5 in the marine cyanobacterium Synechococcus sp. strain UTEX 2380. Net proton efflux in the light was completely abolished by the uncoupler carbonylcyanide m-chlorophenylhydrazone and the membrane ATPase inhibitor diethylstilbestrol or partially abolished by the membrane ATPase inhibitor N,N′-dicyclohexyl-carbodiimide and by orthovanadate. H+ extrusion in the light was accompanied by K+ uptake at rates of 30 μmol∙mg chlorophyll−1∙h−1. During the steady state of CO2 fixation, potassium was excreted simultaneously with medium alkalization. The K+ content of the cells was 432 mM for air-grown cells. K+ in the cells was displaced by diethanolamine, which was inhibited by m-chlorophenylhydrazone. Na+-loaded cells showed nearly complete inactivation of oxygen evolution and medium alkalization. Both activities were reactivated by the addition of K+ or Rb+. A fivefold increase in inorganic carbon uptake in the light was observed in the presence of K+. The pH of the cytoplasm in the light increased from 7.2 to 8.04 in the pH range 6.6–8.6. These results suggest that a light-dependent, proton-excreting ATPase is active in conjunction with a K+ uptake system in a marine Synechococcus species, while a K+–H+ antiporter may function as a regulator of cytoplasmic pH during photosynthesis.Key words: potassium transport, oxygen, cyanobacterium, Synechococcus, proton extrusion.

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Photosynthetic Oxygen Evolution Is Stabilized by Cytochrome c550 against Heat Inactivation in Synechococcus sp. PCC 7002

PLANT PHYSIOLOGY ◽

10.1104/pp.105.4.1313 ◽

1994 ◽

Vol 105 (4) ◽

pp. 1313-1319 ◽

Cited By ~ 52

Author(s):

Y. Nishiyama ◽

H. Hayashi ◽

T. Watanabe ◽

N. Murata

Keyword(s):

Oxygen Evolution ◽

Heat Inactivation ◽

Photosynthetic Oxygen Evolution ◽

Synechococcus Sp ◽

Photosynthetic Oxygen

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Random Insertional Mutagenesis Used in the Generation of Mutants of the Marine Cyanobacterium Synechococcus sp. Strain PCC7002 With an Impaired CO2 Concentrating Mechanism

Functional Plant Biology ◽

10.1071/pp96124 ◽

1997 ◽

Vol 24 (3) ◽

pp. 317 ◽

Cited By ~ 10

Author(s):

Dieter Sültemeyer ◽

Barbara Klughammer ◽

Martha Ludwig ◽

Murray R. Badger ◽

G. Dean Price

Keyword(s):

Insertional Mutagenesis ◽

Physiological Characteristics ◽

Transport Systems ◽

Uptake System ◽

Wild Type ◽

Marine Cyanobacterium ◽

Co2 Concentrating Mechanism ◽

High Affinity ◽

Concentrating Mechanism ◽

Synechococcus Sp

Random insertional mutagenesis (gene tagging) has been used to generate ten kanamycin resistant mutants of the marine cyanobacterium, Synechococcus sp. strain PCC7002, defective in components of the CO2 concentrating mechanism (CCM). Three mutants had physiological characteristics consistent with defects in carboxysome functioning such as the ability to over-accumulate inorganic carbon (Ci) but make little use of this pool for photosynthesis. Another group of mutants could not survive at 20 mL CO2 L-1 (low Ci) even though they were able to induce high-affinity CO2 and HCO3- transport systems within 6 h of acclimation to low Ci, albeit at reduced maximum rates compared to wild type (WT) cells. A third class of mutant grew more slowly at 20 mL CO2 L-1 (pH 8.2) than WT cells and failed to grow at pH 7.0 under the same CO2 conditions. Besides inhibition of Ci transport rates in low-Ci cells and small internal Ci pools, these mutants had only partly developed a high-affinity HCO3- uptake system and had completely failed to induce a high-affinity CO2 transport system. Physiological characteristics of these mutants are discussed along with prospects for isolating the genes affected in these mutants.

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Dependence of the Flash-Induced Oxygen Evolution Pattern on the Chemically and Far Red Light-Modulated Redox Condition in Cyanobacterial Photosynthetic Electron Transport

Zeitschrift für Naturforschung C ◽

10.1515/znc-2003-1-217 ◽

2003 ◽

Vol 58 (1-2) ◽

pp. 93-102 ◽

Cited By ~ 4

Author(s):

Susanne Spiegel ◽

Klaus P. Bader

Keyword(s):

Oxygen Evolution ◽

Redox Condition ◽

Photosynthetic Oxygen Evolution ◽

Background Illumination ◽

Relaxation Kinetics ◽

Oscillatoria Chalybea ◽

Synechococcus Sp ◽

Pcc 7942 ◽

Synechocystis Sp ◽

Pcc 6803

Flash-induced photosynthetic oxygen evolution was measured in cells and thylakoid preparations from the coccoid cyanobacteria Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7942 and from the filamentous cyanobacterium Oscillatoria chalybea. The resulting characteristic flash patterns from these cyanobacteria can be chemically altered by addition of exogenously added substances like CCCP, DCPiP and inorganic salts. Potassium chloride, manganese sulfate and calcium chloride affected the sequences by specific increases in the flash yield and/or effects on the transition parameters. Chloride appeared to exert the strongest stimulatory effect on the oxygen yield. In comparison to chloride, both manganese and calcium did not significantly stimulate the flash amplitudes as such, but improved the functioning of the oxygen evolving complex by decreasing the miss parameter α. Particular effects were observed with respect to the time constants of the relaxation kinetics of the first two flash signals Y1/Y2 of the cyanobacterial patterns. In the presence of the investigated chemicals the amplitudes of the first two flash signals (Y2 in particular) were increased and the relaxation kinetics were enhanced so that the time constant became about identical to the conditions of steady state oxygen flash amplitudes. The results provide further evidence against a possible participation of either PS I or respiratory processes to Y1/Y2 of cyanobacterial flash patterns. Dramatic effects were observed when protoplasts from Oscillatoria chalybea or cells from Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7942 were exposed to weak far red background illumination. Under these conditions, Y2 (and to a smaller extent Y1) of otherwise unchanged flash sequences were specifically modified. Y2 was substantially increased and again the relaxation kinetics were accelerated making the signal indistinguishable from a Yss signal. From the mathematical fit of the sequences we conclude that S2 contributes to 10-20% of the S-state distribution (in comparison to 0% in the control). Thus, far red background illumination might represent a valuable means for photosynthetic investigations where high amounts of S2 are required like e.g. EPR measurements. In such experiments the corresponding EPR signals appeared substantially enhanced following far red preillumination (Ahrling and Bader, unpublished observations). Our results clearly show that the ‚controversial results‘ from parts of the literature suggesting the participation of different mechanisms (net oxygen evolution, inhibited uptake processes etc.) are not required to explain the flash-induced oxygen evolution in cyanobacteria: the seemingly ‚incompatible‘ conditions and conformations can be perfectly interconverted by different modulation techniques (chemicals, far red) of the respective redox condition within the water oxidation complex of photosynthesis

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Regulation of cytosolic free Ca2+ concentration in acinar cells of rat pancreas

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1983.245.3.g347 ◽

1983 ◽

Vol 245 (3) ◽

pp. G347-G357 ◽

Cited By ~ 3

Author(s):

H. Streb ◽

I. Schulz

Keyword(s):

Steady State ◽

Incubation Medium ◽

Minimal Medium ◽

Acinar Cells ◽

Pancreatic Acinar Cells ◽

Atpase Inhibitor ◽

Rat Pancreas ◽

Mitochondrial Inhibitors ◽

Pancreatic Cells ◽

State Concentration

Ca2+ uptake into isolated exocrine pancreatic cells with highly permeable plasma membrane was determined by measuring the decrease in free Ca2+ concentration of the surrounding incubation medium with a Ca2+-specific electrode. In the presence of Mg-ATP and respiratory substrates the free Ca2+ concentration of the incubation medium decreased rapidly after addition of leaky cells until a stable medium free Ca2+ concentration of 4.2 +/- 0.1 X 10(-7) mol/l was obtained. Changes in the medium free Ca2+ concentration at steady state by addition of Ca2+ or EGTA were buffered by cellular uptake or release, respectively, until the steady-state free Ca2+ concentration was reestablished. When nonmitochondrial Ca2+ uptake was determined in the presence of a combination of mitochondrial inhibitors (10(-5) mol/l antimycin, 5 X 10(-6) mol/l oligomycin, and 10(-2) mol/l azide), the rate of uptake was considerably reduced, while the steady-state concentration was unaltered. In contrast, mitochondrial uptake that could be observed in the presence of the ATPase inhibitor vanadate (2 X 10(-3) mol/l) proceeded at the same rate as the control, but the minimal medium free Ca2+ concentration reached was 2.4 +/- 0.1 X 10(-7) mol/l higher than the control. Addition of secretagogues at steady-state free Ca2+ concentration resulted in a Ca2+ release of 0.73 +/- 0.08 nmol/mg protein. The increase in medium free Ca2+ concentration was entirely transient and followed by reuptake to the prestimulation level. The data indicate that a cytosolic free Ca2+ concentration of 4 X 10(-7) mol/l can be regulated in pancreatic acinar cells by a nonmitochondrial Mg2+-dependent Ca2+ pool.

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