Relief and calcium from gypsum as key factors for net inorganic carbon accumulation in soils of a semiarid Mediterranean environment

Geoderma ◽  
2021 ◽  
Vol 398 ◽  
pp. 115115
Author(s):  
Vito Armando Laudicina ◽  
Carmelo Dazzi ◽  
Antonio Delgado ◽  
Haydn Barros ◽  
Riccardo Scalenghe
Keyword(s):  
Inorganic Carbon ◽  
Carbon Accumulation ◽  
Mediterranean Environment ◽  
Key Factors

scholarly journals pH determines the energetic efficiency of the cyanobacterial CO2 concentrating mechanism

2016 ◽  
Vol 113 (36) ◽  
pp. E5354-E5362 ◽  
Author(s):  
Niall M. Mangan ◽  
Avi Flamholz ◽  
Rachel D. Hood ◽  
Ron Milo ◽  
David F. Savage
Keyword(s):  
Intracellular Ph ◽  
Inorganic Carbon ◽  
Quantitative Description ◽  
Carbon Accumulation ◽  
Energetic Efficiency ◽  
Ribulose Bisphosphate Carboxylase ◽  
Competitive Reaction ◽  
Bisphosphate Carboxylase ◽  
Concentrating Mechanism ◽  
Ribulose Bisphosphate Carboxylase Oxygenase

Many carbon-fixing bacteria rely on a CO2 concentrating mechanism (CCM) to elevate the CO2 concentration around the carboxylating enzyme ribulose bisphosphate carboxylase/oxygenase (RuBisCO). The CCM is postulated to simultaneously enhance the rate of carboxylation and minimize oxygenation, a competitive reaction with O2 also catalyzed by RuBisCO. To achieve this effect, the CCM combines two features: active transport of inorganic carbon into the cell and colocalization of carbonic anhydrase and RuBisCO inside proteinaceous microcompartments called carboxysomes. Understanding the significance of the various CCM components requires reconciling biochemical intuition with a quantitative description of the system. To this end, we have developed a mathematical model of the CCM to analyze its energetic costs and the inherent intertwining of physiology and pH. We find that intracellular pH greatly affects the cost of inorganic carbon accumulation. At low pH the inorganic carbon pool contains more of the highly cell-permeable H2CO3, necessitating a substantial expenditure of energy on transport to maintain internal inorganic carbon levels. An intracellular pH ≈8 reduces leakage, making the CCM significantly more energetically efficient. This pH prediction coincides well with our measurement of intracellular pH in a model cyanobacterium. We also demonstrate that CO2 retention in the carboxysome is necessary, whereas selective uptake of HCO3− into the carboxysome would not appreciably enhance energetic efficiency. Altogether, integration of pH produces a model that is quantitatively consistent with cyanobacterial physiology, emphasizing that pH cannot be neglected when describing biological systems interacting with inorganic carbon pools.

Environmental regulation of CO2-concentrating mechanisms in microalgae

1998 ◽  
Vol 76 (6) ◽  
pp. 1010-1017 ◽  
Author(s):  
John Beardall ◽  
Andrew Johnston ◽  
John Raven
Keyword(s):  
Inorganic Carbon ◽  
Light Availability ◽  
Phosphorus Limitation ◽  
Aeration Rate ◽  
Carbon Accumulation ◽  
Ribulose Bisphosphate Carboxylase ◽  
Carbon Utilization ◽  
Bisphosphate Carboxylase ◽  
Inorganic Carbon Transport ◽  
Carbon Transport

Most microalgae possess a mechanism for actively transporting inorganic carbon that concentrates CO2 at the active site of the carbon fixing enzyme ribulose bisphosphate carboxylase-oxygenase (Rubisco). This review considers the effects of environmental factors on the capacity and activity of microalgal CO2-concentrating mechanisms. Limitation of energy supply by light availability decreases the rate of inorganic carbon transport and cells grown under light-limited conditions have a reduced capacity for CO2 accumulation. Phosphorus limitation also reduces the capacity of algal cells to accumulate CO2, whereas both the rate of supply of nitrogen and the form in which it is made available interact in various complex ways with carbon utilization. The potential role of other nutrients in modulating inorganic carbon transport is also discussed. The capacity of algae for carbon accumulation is also affected by CO2 supply, which, in turn, is a function of the interactions between ionic strength of the growth medium, pH, cell density in culture, aeration rate, and inorganic carbon concentration in the medium. The effects of these interacting parameters are discussed, together with an assessment of the possible roles and significance of CO2-concentrating mechanisms to microalgae in marine and freshwater ecosystems.Key words: carbon acquisition, microalgae, CO2-concentrating mechanism, light, nutrient limitation, CO2 supply.

Inorganic carbon transport in some marine microalgal species

1991 ◽  
Vol 69 (5) ◽  
pp. 1032-1039 ◽  
Author(s):  
M. J. Merrett
Keyword(s):  
Carbonic Anhydrase ◽  
Inorganic Carbon ◽  
Silicone Oil ◽  
Ph Regulation ◽  
Carbonic Anhydrase Activity ◽  
Carbon Accumulation ◽  
Bicarbonate Transport ◽  
High Affinity ◽  
Inorganic Carbon Transport ◽  
Carbon Transport

Inorganic carbon transport was investigated in a range of marine microalgae. A small-celled strain of Stichococcus bacillaris, containing appreciable carbonic anhydrase activity, showed a high affinity for CO2, while measurement of the internal inorganic carbon pool by the silicone oil layer centrifugal filtering technique showed cells concentrated inorganic carbon up to 20-fold in relation to the external medium at pH 5.0 but not pH 8.3. The addition of 14CO2 or H14CO3− to cells in short-term kinetic experiments at pH 8.3 confirmed that only CO2 provides the exogenous substrate for substantial inorganic carbon accumulation within the cell. High-affinity HCO3− transport in Phaeodactylum tricornutum and Porphyridium purpureum is dependent on sodium ions, while intracellular carbonic anhydrase increased the steady-state flux of CO2 from inside the plasmalemma to Rubisco. In the presence of HCO3− the intracellular pH in cells of P. purpureum is 7.1 but on carbon starvation the pH falls to 6.0. Ethoxyzolamide blocks bicarbonate-dependent alkalinization of the cytosol, confirming a central role for carbonic anhydrase–bicarbonate in cytosolic pH regulation. Carbonic anhydrase activity is pH dependent in P. purpureum so synergistic interaction between CO2 uptake and bicarbonate transport may occur.

Inorganic carbon accumulation and photosynthesis by Chlorella pyrenoidosa

1985 ◽  
Vol 63 (7) ◽  
pp. 1249-1254 ◽  
Author(s):  
Barry J. Shelp ◽  
David T. Canvin
Keyword(s):  
Inorganic Carbon ◽  
Silicone Oil ◽  
Cell Types ◽  
Chlorella Pyrenoidosa ◽  
Carbon Pool ◽  
Carbon Accumulation ◽  
Alkaline Ph ◽  
Nonspecific Binding ◽  
Chemical Treatments ◽  
Centrifugation Technique

Photosynthesis and intracellular inorganic carbon were measured in air-grown and high CO2 grown Chlorella pyrenoidosa under various environmental and chemical treatments, using a silicone-oil centrifugation technique. At alkaline pH, both cell types accumulated inorganic carbon, presumably [Formula: see text], in a light-dependent and saturable process. The formation of the internal pool was kinetically observed and was used as a substrate for photosynthesis. Rates of carbon influx always exceeded the rates of photosynthesis in air-grown cells, whereas in high CO2 grown cells influx rates closely paralleled photosynthesis. At acid pH inorganic carbon was also accumulated, but the characteristics of this accumulation differed from that seen at alkaline pHs. It was more rapid and was not affected by any of the treatments that affected accumulation at higher pHs. However, the internal inorganic carbon pool provided CO2 for photosynthesis. It is suggested that this accumulation can be explained partly by CO2 diffusion according to the pH gradient existing across the plasmalemma and partly by nonspecific binding of CO2 to proteins and amino acids. The results are consistent with the view that air-grown C. pyrenoidosa is capable of utilizing either CO2 or [Formula: see text] as a substrate for the internal inorganic carbon pool.

Evidence for bicarbonate accumulation by Anacystis nidulans

1984 ◽  
Vol 62 (7) ◽  
pp. 1398-1403 ◽  
Author(s):  
Barry J. Shelp ◽  
David T. Canvin
Keyword(s):  
Inorganic Carbon ◽  
Carbon Fixation ◽  
External Medium ◽  
Anacystis Nidulans ◽  
Carbon Pool ◽  
Carbon Accumulation ◽  
Total Carbon ◽  
Apparent Affinity ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon

Kinetic studies of photosynthetic O2 evolution as a function of pH were conducted to investigate the nature of the inorganic carbon used during photosynthesis by Anacystis nidulans. At pH 5, the apparent affinity for carbon during photosynthesis was similar in air-grown and high CO2 grown cells, but at alkaline pH, the apparent affinity was much greater in air-grown cells. The substrate concentration for half-maximum rates of photosynthesis in air-grown cells remained constant as a function of pH when the substrate was expressed as total carbon, suggesting that these cells were capable of using varying proportions of CO2 and [Formula: see text]. Photosynthesis in high CO2 grown algae appeared to be more dependent on CO2 over the pH range, indicating that CO2 was the predominant carbon species used, but [Formula: see text] uptake was also indicated. Internal inorganic carbon and photosynthetic carbon fixation in air-grown cells were determined at pH 8.5, using silicone oil centrifugation. Anacystis accumulated inorganic carbon in large excess of that in the external medium by a mechanism which is sensitive to inhibitors of energy metabolism and independent of concurrent carbon fixation; light was required to accumulate and maintain the internal carbon pool. The degree of accumulation was a function of the carbon concentration in the external medium; at 12 μM external carbon, the accumulation ratio was in excess of 100-fold, whereas at 4.76 mM, the ratio was only 5-fold. The rates of carbon transport were always sufficient to maintain photosynthesis. Carbon efflux rates approaching 40% of the influx rate were found at equilibrium internal carbon concentrations. Kinetic parameters of photosynthesis are discussed with reference to the known properties of algal ribulose bisphosphate (RuBP) carboxylase–oxygenase. It is concluded that the internal inorganic carbon pool serves as an intermediate for photosynthetic carbon fixation and that, if CO2 and [Formula: see text] are in equilibrium, the carbon accumulation at ambient CO2 and O2 is sufficient to suppress RuBP oxygenase activity.

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