Evidence for active CO2 uptake by a CO2-ATPase in the acidophilic green alga Eremosphaera viridis

2001 ◽  
Vol 79 (11) ◽  
pp. 1274-1281
Author(s):  
Jason ST Deveau ◽  
Roger R Lew ◽  
Brian Colman
Keyword(s):  
Atpase Activity ◽  
Green Alga ◽  
Inorganic Carbon ◽  
Atp Hydrolysis ◽  
Dissolved Inorganic Carbon ◽  
Electrical Potential ◽  
Fold Increase ◽  
Co2 Uptake ◽  
Eremosphaera Viridis ◽  
A Value

We examined the mechanism(s) responsible for active uptake of dissolved inorganic carbon (DIC) during photosynthesis in the green alga Eremosphaera viridis De Bary. O2 electrode measurements of algal oxygen evolution and CO2 fluxes as a function of DIC availability indicate that E. viridis actively imports only CO2 during photosynthesis, and does not possess external carbonic anhydrase (CA). The K0.5[CO2] was 14.2 and 10.1 µM at pH 5.0 and 8.0, respectively. Both membrane potential and cellular resistance were measured under controlled conditions of [CO2] at either 2 or 15 µM. Active CO2 uptake was electrically silent, suggesting that CO2 uptake might be mediated by a CO2-ATPase. Comparison of ATPase activity in microsomal preparations at low (0 µM) and high (15 µM) [CO2] indicated a 1.25-fold increase in ATP hydrolysis in high [CO2]. The CO2-ATPase activity was inhibited by the broad-acting inhibitors diethylstilbestrol (DES) and N',N'-dicyclohexylcarbodiimide (DCCD) but unaffected by vanadate, fluoride, and nitrate. The K0.5[CO2] of the ATPase activity was 22.5 µM, a value very similar to the K0.5[CO2] for CO2 uptake by whole algal cells. These results suggest the existence of a CO2-ATPase as the major importer of DIC for photosynthesis in the microalga E. viridis.Key words: chlorophyte, CO2 transport, CO2-ATPase, photosynthesis, electrical potential, mass spectrometry.

CO2 uptake mechanism in Eremosphaera viridis

1998 ◽  
Vol 76 (6) ◽  
pp. 1161-1164
Author(s):  
Jason ST Deveau ◽  
Houman Khosravani ◽  
Roger R Lew ◽  
Brian Colman
Keyword(s):  
Membrane Potential ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Pond Water ◽  
Co2 Uptake ◽  
Uptake Mechanism ◽  
Nitrogen Gas ◽  
Eremosphaera Viridis ◽  
Electrophysiological Measurements ◽  
Free Environment

Electrophysiological measurements of the acidophilic alga Eremosphaera viridis De Bary explored the effects of low CO2 levels on both membrane potential and resistance. This procedure incorporates a double-barreled microelectrode and suction pipette system, coupled with an approximately CO2-free environment. A key requirement is an artificial pond water perfusion media that has been purged of dissolved inorganic carbon by being boiled and bubbled with nitrogen gas. Both membrane potential and resistance were measured at pH5 in both low-CO2 conditions (2µM) and high-CO2 conditions (14µM) in both light, where CO2 transport is known to be active, and dark, where CO2 transport is not active. To avoid dissolved inorganic carbon contamination of the perfusion media, a special chamber was constructed, featuring a laminar flow of nitrogen gas over the solution, which allowed for the manipulation of cells while preventing any contamination by CO2 from the air. Results indicate that the uptake of CO2 by the alga is electrically silent and, therefore, not the result of a symport or antiport cotransport system that would "drive" CO2 uptake by coupling it to the electrochemical gradient of ions such as protons or sodium. The uptake is most likely facilitated by a transporter directly coupled with ATP hydrolysis.Key words: Eremosphaera viridis, dissolved inorganic carbon, CO2-ATPase, electrophysiology.

scholarly journals CO2 Uptake and Fixation by Endosymbiotic Chemoautotrophs from the Bivalve Solemya velum

2006 ◽  
Vol 73 (4) ◽  
pp. 1174-1179 ◽  
Author(s):  
Kathleen M. Scott ◽  
Colleen M. Cavanaugh
Keyword(s):  
Inorganic Carbon ◽  
Carbon Fixation ◽  
Dissolved Inorganic Carbon ◽  
Co2 Uptake ◽  
Maximal Velocity ◽  
Marine Habitats ◽  
Half Saturation Constant ◽  
Oxygen Conditions ◽  
Solemya Velum ◽  
Influence Of Ph

ABSTRACT Chemoautotrophic symbioses, in which endosymbiotic bacteria are the major source of organic carbon for the host, are found in marine habitats where sulfide and oxygen coexist. The purpose of this study was to determine the influence of pH, alternate sulfur sources, and electron acceptors on carbon fixation and to investigate which form(s) of inorganic carbon is taken up and fixed by the gamma-proteobacterial endosymbionts of the protobranch bivalve Solemya velum. Symbiont-enriched suspensions were generated by homogenization of S. velum gills, followed by velocity centrifugation to pellet the symbiont cells. Carbon fixation was measured by incubating the cells with 14C-labeled dissolved inorganic carbon. When oxygen was present, both sulfide and thiosulfate stimulated carbon fixation; however, elevated levels of either sulfide (>0.5 mM) or oxygen (1 mM) were inhibitory. In the absence of oxygen, nitrate did not enhance carbon fixation rates when sulfide was present. Symbionts fixed carbon most rapidly between pH 7.5 and 8.5. Under optimal pH, sulfide, and oxygen conditions, symbiont carbon fixation rates correlated with the concentrations of extracellular CO2 and not with HCO3 − concentrations. The half-saturation constant for carbon fixation with respect to extracellular dissolved CO2 was 28 � 3 μM, and the average maximal velocity was 50.8 � 7.1 μmol min−1 g of protein−1. The reliance of S. velum symbionts on extracellular CO2 is consistent with their intracellular lifestyle, since HCO3 − utilization would require protein-mediated transport across the bacteriocyte membrane, perisymbiont vacuole membrane, and symbiont outer and inner membranes. The use of CO2 may be a general trait shared with many symbioses with an intracellular chemoautotrophic partner.

scholarly journals Impact of seawater carbonate chemistry on the calcification of marine bivalves

2015 ◽  
Vol 12 (2) ◽  
pp. 1543-1571 ◽  
Author(s):  
J. Thomsen ◽  
K. Haynert ◽  
K. M. Wegner ◽  
F. Melzner
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Shell Growth ◽  
System Component ◽  
Natural Seawater ◽  
Co2 Uptake ◽  
Similar Response ◽  
Carbonate Chemistry ◽  
Response Curves ◽  
Physiological Processes

Abstract. Bivalve calcification, particular of the early larval stages is highly sensitive to the change of ocean carbonate chemistry resulting from atmospheric CO2 uptake. Earlier studies suggested that declining seawater [CO32−] and thereby lowered carbonate saturation affect shell production. However, disturbances of physiological processes such as acid-base regulation by adverse seawater pCO2 and pH can affect calcification in a secondary fashion. In order to determine the exact carbonate system component by which growth and calcification are affected it is necessary to utilize more complex carbonate chemistry manipulations. As single factors, pCO2 had no and [HCO3−] and pH only limited effects on shell growth, while lowered [CO32−] strongly impacted calcification. Dissolved inorganic carbon (CT) limiting conditions led to strong reductions in calcification, despite high [CO32−], indicating that [HCO3−] rather than [CO32−] is the inorganic carbon source utilized for calcification by mytilid mussels. However, as the ratio [HCO3−] / [H+] is linearly correlated with [CO32−] it is not possible to differentiate between these under natural seawater conditions. Therefore, the availability of [HCO3−] combined with favorable environmental pH determines calcification rate and an equivalent of about 80 μmol kg−1 [CO32−] is required to saturate inorganic carbon supply for calcification in bivalves. Below this threshold biomineralization rates rapidly decline. A comparison of literature data available for larvae and juvenile mussels and oysters originating from habitats differing substantially with respect to prevailing carbonate chemistry conditions revealed similar response curves. This suggests that the mechanisms which determine sensitivity of calcification in this group are highly conserved. The higher sensitivity of larval calcification seems to primarily result from the much higher relative calcification rates in early life stages. In order to reveal and understand the mechanisms that limit or facilitate adaptation to future ocean acidification, it is necessary to better understand the physiological processes and their underlying genetics that govern inorganic carbon assimilation for calcification.

scholarly journals Hyperthyroidism increases the uncoupled ATPase activity and heat production by the sarcoplasmic reticulum Ca2+-ATPase

2003 ◽  
Vol 375 (3) ◽  
pp. 753-760 ◽  
Author(s):  
Ana Paula ARRUDA ◽  
Wagner S. da-SILVA ◽  
Denise P. CARVALHO ◽  
Leopoldo de MEIS
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Heat Production ◽  
Atp Hydrolysis ◽  
Fold Increase ◽  
Heat Sources ◽  
Muscle Type ◽  
Red Muscle

The sarcoplasmic reticulum Ca2+-ATPase is able to modulate the distribution of energy released during ATP hydrolysis, so that a portion of energy is used for Ca2+ transport (coupled ATPase activity) and a portion is converted into heat (uncoupled ATPase activity). In this report it is shown that T4 administration to rabbits promotes an increase in the rates of both the uncoupled ATPase activity and heat production in sarcoplasmic reticulum vesicles, and that the degree of activation varies depending on the muscle type used. In white muscles hyperthyroidism promotes a 0.8-fold increase of the uncoupled ATPase activity and in red muscle a 4-fold increase. The yield of vesicles from hyperthyroid muscles is 3–4-fold larger than that obtained from normal muscles; thus the rate of heat production by the Ca2+-ATPase expressed in terms of g of muscle in hyperthyroidism is increased by a factor of 3.6 in white muscles and 12.0 in red muscles. The data presented suggest that the Ca2+-ATPase uncoupled activity may represent one of the heat sources that contributes to the enhanced thermogenesis noted in hyperthyroidism.

Quantification of decadal anthropogenic CO2 uptake in the ocean based on dissolved inorganic carbon measurements

Nature ◽  
10.1038/25103 ◽  
1998 ◽  
Vol 396 (6711) ◽  
pp. 560-563 ◽  
Author(s):  
Tsung-Hung Peng ◽  
Rik Wanninkhof ◽  
John L. Bullister ◽  
Richard A. Feely ◽  
Taro Takahashi
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Co2 Uptake ◽  
Anthropogenic Co2

Regulation of inorganic carbon acquisition by phosphorus limitation in the green alga Chlorella emersonii

2005 ◽  
Vol 83 (7) ◽  
pp. 859-864 ◽  
Author(s):  
John Beardall ◽  
Simon Roberts ◽  
John A Raven
Keyword(s):  
Green Alga ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Stable Carbon Isotope ◽  
Phosphorus Limitation ◽  
Phosphate Limitation ◽  
P Limitation ◽  
Green Alga Chlorella ◽  
In Cells ◽  
Inorganic Carbon Acquisition

Inorganic phosphate (Pi) plays a central role in cellular energy transduction. As a consequence, limitation of growth by phosphate availability can have an important impact on various aspects of metabolism. Since carbon acquisition via CO2-concentrating mechanisms (CCMs) in most microalgae is an active process, requiring ATP, it might be expected that phosphate limitation could have an indirect regulatory influence on CCM activity. We grew the green alga Chlorella emersonii Shihira et Krauss in semicontinuous or continuous cultures in nutrient-replete conditions or with orthophosphate as the limiting nutrient. CCM activity was down-regulated by P limitation. K0.5(dissolved inorganic carbon) values increased from approximately 4.5 µmol·L–1 in cells growing at close to maximal rates to >12 µmol·L–1 in cells growing at 0.2 d–1. Maximal rates of photosynthesis decreased by approximately half over the same range of growth rates. Direct measurements of CCM activity showed that internal CO2 : external CO2 ratio was markedly decreased under P limitation, and concurrent measurements of stable carbon isotope discrimination were consistent with decreased CCM activity in the P-limited cells.Key words: phosphate, CCM, CO2-concentrating mechanism, Chlorella, inorganic carbon acquisition.

scholarly journals Impact of seawater carbonate chemistry on the calcification of marine bivalves

2015 ◽  
Vol 12 (14) ◽  
pp. 4209-4220 ◽  
Author(s):  
J. Thomsen ◽  
K. Haynert ◽  
K. M. Wegner ◽  
F. Melzner
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Shell Growth ◽  
System Component ◽  
Natural Seawater ◽  
Co2 Uptake ◽  
Similar Response ◽  
Carbonate Chemistry ◽  
Response Curves ◽  
Physiological Processes

Abstract. Bivalve calcification, particularly of the early larval stages, is highly sensitive to the change in ocean carbonate chemistry resulting from atmospheric CO2 uptake. Earlier studies suggested that declining seawater [CO32−] and thereby lowered carbonate saturation affect shell production. However, disturbances of physiological processes such as acid-base regulation by adverse seawater pCO2 and pH can affect calcification in a secondary fashion. In order to determine the exact carbonate system component by which growth and calcification are affected it is necessary to utilize more complex carbonate chemistry manipulations. As single factors, pCO2 had no effects and [HCO3-] and pH had only limited effects on shell growth, while lowered [CO32−] strongly impacted calcification. Dissolved inorganic carbon (CT) limiting conditions led to strong reductions in calcification, despite high [CO32−], indicating that [HCO3-] rather than [CO32−] is the inorganic carbon source utilized for calcification by mytilid mussels. However, as the ratio [HCO3-] / [H+] is linearly correlated with [CO32−] it is not possible to differentiate between these under natural seawater conditions. An equivalent of about 80 μmol kg−1 [CO32−] is required to saturate inorganic carbon supply for calcification in bivalves. Below this threshold biomineralization rates rapidly decline. A comparison of literature data available for larvae and juvenile mussels and oysters originating from habitats differing substantially with respect to prevailing carbonate chemistry conditions revealed similar response curves. This suggests that the mechanisms which determine sensitivity of calcification in this group are highly conserved. The higher sensitivity of larval calcification seems to primarily result from the much higher relative calcification rates in early life stages. In order to reveal and understand the mechanisms that limit or facilitate adaptation to future ocean acidification, it is necessary to better understand the physiological processes and their underlying genetics that govern inorganic carbon assimilation for calcification.

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