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John A. Raven - One of the best experts on this subject based on the ideXlab platform.
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Inorganic Carbon acquisition by eukaryotic algae: four current questions
Photosynthesis Research, 2010Co-Authors: John A. RavenAbstract:The phylogenetically and morphologically diverse eukaryotic algae are typically oxygenic photolithotrophs. They have a diversity of incompletely understood mechanisms of Inorganic Carbon acquisition: this article reviews four areas where investigations continue. The first topic is diffusive CO_2 entry. Most eukaryotic algae, like all cyanobacteria, have Inorganic Carbon concentrating mechanisms (CCMs). The ancestral condition was presumably the absence of a CCM, i.e. diffusive CO_2 entry, as found in a small minority of eukaryotic algae today; however, it is likely that, as is found in several cases, this condition is due to a loss of a CCM. There are a number of algae which are in various respects intermediate between diffusive CO_2 entry and occurrence of a CCM: further study is needed on this aspect. A second topic is the nature of cyanelles and their role in Inorganic Carbon assimilation. The cyanelles (plastids) of the euglyphid amoeba Paulinella have been acquired relatively recently by endosymbiosis with genetic integration of an α-cyanobacterium with a Form 1A Rubisco. The α-carboxysomes in the cyanelles are presumably involved in a CCM, but further investigation is needed.Also called cyanelles are the plastids of glaucocystophycean algae, but is it now clear that these were derived from the β-cyanobacterial ancestor of all plastids other than that of Paulinella. The resemblances of the central body of the cyanelles of glaucocystophycean algae to carboxysomes may not reflect derivation from cyanobacterial β-carboxysomes; although it is clear that these algae have CCMs but these are now well characterized. The other two topics concern CCMs in other eukaryotic algae; these CCMs arose polyphyletically and independently of the cyanobacterial CCMs. It is generally believed that eukaryotic algal, like cyanobacterial, CCMs are based on active transport of an Inorganic Carbon species and/or protons, and they have C_3 biochemistry. This is the case for the organism considered as the third topic, i.e. Chlamydomonas reinhardtii , the eukaryotic alga with the best understood CCM. This CCM involves HCO_3 ^− conversion to CO_2 in the thylakoid lumen so the external Inorganic Carbon must cross four membranes in series with a final CO_2 effux from the thylakoid. More remains to be investigated about this CCM. The final topic is that of the occurrence of C_4-like metabolism in the CCMs of marine diatoms. Different conclusions have been reached depending on the organism investigated and the techniques used, and several aspects require further study.
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Sensing Inorganic Carbon: CO2 and HCO3−
The Biochemical journal, 2006Co-Authors: John A. RavenAbstract:Enzymes and transporters that catalyse reactions involving Inorganic Carbon are well characterized with respect to the species of Inorganic Carbon (CO2 or HCO3−) with which they interact. There is less information on the species recognized by proteins that sense Inorganic Carbon. In this issue of the Biochemical Journal, Hammer and colleagues show conclusively that cyanobacterial adenylyl cyclases are activated by CO2 and not HCO3−, as was believed previously. While in some circumstances a similar in vivo regulatory outcome is achieved from sensing HCO3− as from sensing CO2, there are cases in which the outcomes are significantly different. The most striking example is where a compartment lacks Carbonic anhydrase yet supports large metabolic fluxes of Inorganic Carbon species so that CO2 and HCO3− are not at equilibrium. Other examples involve changes in pH, or temperature, of a compartment containing an equilibrium mixture of CO2 and HCO3−.
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Inorganic Carbon concentrating mechanisms in relation to the biology of algae.
Photosynthesis research, 2003Co-Authors: John A. RavenAbstract:Significant advances have recently been made in our understanding of the mechanism of Inorganic Carbon transport in algae and, especially, cyanobacteria with Inorganic Carbon concentrating mechanisms (CCMs). Furthermore, the role of CCMs in increasing the rate of photosynthesis in air-equilibrated solutions is also quite well understood. However, less often considered is how the presence (or absence) of a CCM relates to the biology of algae. This mini-review relates the occurrence of algal CCMs to phylogeny, life form, life history, and interactions with other organisms. While some patterns can be seen, the occurrence of CCMs in relation to the overall biology of the algae needs more investigation.
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SOURCES OF Inorganic Carbon FOR PHOTOSYNTHESIS BY THREE SPECIES OF MARINE DIATOM1
Journal of Phycology, 1997Co-Authors: Rebecca E. Korb, Andrew M. Johnston, Peter J. Saville, John A. RavenAbstract:The utilization of Inorganic Carbon by three species of marine diatom, Skeletonema costatum (Grev.) Cleve. Ditylum brightwellii (West) Grun., and Chaetoceros calcitrans Paulsen was investigated using an Inorganic Carbon isotopic disequilibnum technique and Inorganic Carbon dose-response curves. Stable Carbon isotope data of the diatoms are also presented. Observed rates of photosynthetic oxygen evolution were greater than could be accounted for by the theoretical rate of CO2 supply from the uncatalyzed dehydration of HCO3− in the external medium, suggesting use of HCO3− as an Inorganic Carbon source. Data from the isotopic disequilibrium experiment demonstrate the use of both HCO3− and CO2 for photosynthesis. Carbon isotope discrimination values support the use of HCO3− by the diatoms.
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Inorganic Carbon accumulation by the marine diatom Phaeodactylum tricornutum
European Journal of Phycology, 1996Co-Authors: Andrew M. Johnston, John A. RavenAbstract:The ability of the diatom Phaeodactylum tricornutum to accumulate Inorganic Carbon was investigated using the silicone oil centrifugation technique. At internal Inorganic Carbon concentrations less than 0.2 mol m-3 the internal Inorganic Carbon concentration was always greater than expected assuming CO2 assimilation based on diffusion. When tested at 2.0 mol m-3, the normal Inorganic Carbon concentration of seawater, the internal Inorganic Carbon concentration was less than the external concentration. Apparently this alga has the ability to accumulate Inorganic Carbon. When grown in poorly aerated media P. tricornutum is able to reduce the Inorganic Carbon concentration of the media to a greater extent than during growth in well-aerated media. Cells that have experienced Inorganic Carbon depletion are able to accumulate Inorganic Carbon to a greater extent than cells from well-aerated cultures when tested at low external Inorganic Carbon concentrations. Inorganic Carbon photosynthesis dose-response curves...
Xin-ping Wang - One of the best experts on this subject based on the ideXlab platform.
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profile storage of organic Inorganic Carbon in soil from forest to desert
Science of The Total Environment, 2010Co-Authors: Yugang Wang, Yu Chu, Xin-ping WangAbstract:Understanding the distribution of organic/Inorganic Carbon storage in soil profile is crucial for assessing regional, continental and global soil C stores and predicting the consequences of global change. However, little is known about the organic/Inorganic Carbon storages in deep soil layers at various landscapes. This study was conducted to determine the soil organic/Inorganic Carbon storage in soil profile of 0-3m at 5 sites of natural landscape from forest to desert. Landscapes are temperate forest, temperate grassland, temperate shrub-grassland, temperate shrub desert, and temperate desert. Root mass density and Carbon contents at the profile were determined for each site. The results showed that considerable decrease in root biomass and soil organic Carbon content at the soil profile of 0-3m when landscape varied from forest to desert along a precipitation gradient, while soil Inorganic Carbon content increased significantly along the precipitation gradient. Namely, for density of soil organic Carbon: forest>grassland>shrub-grassland>shrub desert>desert; for density of soil Inorganic Carbon: forest, grassland
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Profile storage of organic/Inorganic Carbon in soil: From forest to desert
The Science of the total environment, 2010Co-Authors: Yugang Wang, Yu Chu, Xin-ping WangAbstract:Understanding the distribution of organic/Inorganic Carbon storage in soil profile is crucial for assessing regional, continental and global soil C stores and predicting the consequences of global change. However, little is known about the organic/Inorganic Carbon storages in deep soil layers at various landscapes. This study was conducted to determine the soil organic/Inorganic Carbon storage in soil profile of 0-3m at 5 sites of natural landscape from forest to desert. Landscapes are temperate forest, temperate grassland, temperate shrub-grassland, temperate shrub desert, and temperate desert. Root mass density and Carbon contents at the profile were determined for each site. The results showed that considerable decrease in root biomass and soil organic Carbon content at the soil profile of 0-3m when landscape varied from forest to desert along a precipitation gradient, while soil Inorganic Carbon content increased significantly along the precipitation gradient. Namely, for density of soil organic Carbon: forest>grassland>shrub-grassland>shrub desert>desert; for density of soil Inorganic Carbon: forest, grassland
Aaron Kaplan - One of the best experts on this subject based on the ideXlab platform.
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Inorganic Carbon acquisition systems in cyanobacteria
Photosynthesis Research, 2003Co-Authors: Teruo Ogawa, Aaron KaplanAbstract:This minireview focuses on the mechanism of Inorganic Carbon uptake in cyanobacteria and in particular the two CO_2-uptake systems and two biCarbonate transporters recently identified in Synechocycstis PCC 6803, and their presence in other cyanobacterial strains.
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The Inorganic Carbon-Concentrating Mechanism of Cyanobacteria
The Phototrophic Prokaryotes, 1999Co-Authors: Aaron Kaplan, Michal Ronen-tarazi, Dan Tchernov, David J. Bonfil, Hagit Zer, Daniella Schatz, Assaf Vardi, Miriam Hassidim, Leonora ReinholdAbstract:In this chapter we briefly present and discuss recent progress in the elucidation of certain physiological and molecular aspects of the cyanobacterial Inorganic Carbon (Ci)-concentrating mechanism (CCM). The reader is referred to earlier chapters and reviews [1—14] for a comprehensive account of other important aspects, including the acclimation of cyanobacteria to changing CO2 concentration.
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Physiological and molecular aspects of the Inorganic Carbon-concentrating mechanism in cyanobacteria.
Plant physiology, 1991Co-Authors: Aaron Kaplan, Rakefet Schwarz, Judy Lieman-hurwitz, Leonora ReinholdAbstract:This paper reviews progress made in elucidating the Inorganic Carbon concentrating mechanism in cyanobacteria at the physiological and molecular levels. Emphasis is placed on the mechanism of Inorganic Carbon transport, physiological and genetical analysis of high-CO2-requiring mutants, the polypeptides induced during adaptation to low CO2, the functional significance of carboxysomes, and the role of Carbonic anhydrase. We also make occasional reference to the green algal Inorganic Carbon-concentrating mechanism.
M. Nivedita - One of the best experts on this subject based on the ideXlab platform.
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The transfer rates of Inorganic Carbon and budgetary analysis in a simulated aquatic system
Ecological Modelling, 2007Co-Authors: Biswajit Mukherjee, D. Mukherjee, A. Prasad, M. NiveditaAbstract:Abstract A detailed system analysis of the transfer rates and budget of Inorganic Carbon in a simulated aquatic system was conducted. We used the compartmental model of biogeochemical cycling and a mathematical model designed to calculate transfer rates through various processes. The major processes that account for the change in Inorganic Carbon in the system are: photosynthesis, respiration and decomposition. However, diffusion also plays a part in balancing the system and maintaining a dynamic equilibrium. The change in Inorganic Carbon was measured by the pH–alkalinity method [Culberson, C., Pytkowicz, R.M., Hawley, J.E., 1970. Sea water alkalinity determination by the pH method. J. Mar. Res. V. 17, 737–750] and the Carbon speciation was calculated from pH and alkalinity by a program developed for the process. The results obtained were used to verify the mathematical model. The compartmental model shows a perfect balance of Inorganic Carbon maintained through dynamic equilibrium between the reservoir of Inorganic Carbon and the biota.
M. J. Merrett - One of the best experts on this subject based on the ideXlab platform.
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Inorganic Carbon TRANSPORT IN RELATION TO CULTURE AGE AND Inorganic Carbon CONCENTRATION IN A HIGH‐CALCIFYING STRAIN OF EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE)1
Journal of Phycology, 1996Co-Authors: N. A. Nimer, M. J. Merrett, Colin BrownleeAbstract:The relationships among Inorganic Carbon transport, biCarbonate availability, intracellular pH, and culture age were investigated in high-calcifying cultures of Emiliania huxleyi (Lohmann) Hay & Mohler. Measurement of Inorganic Carbon transport by the silicone-oil centrifugation technique demonstrated that gadolinium, a potential Ca2+ channel inhibitor, blocked intracellular Inorganic Carbon uptake and photosynthetic 14CO2+ fixation in exponential-phase cells. In stationary-phase cells, the intracellular Inorganic Carbon concentration was unaffected by gadolinium. Gadolinium was also used to investigate the link between biCarbonate and Ca2+ transport in high-calcifying cells of E. huxleyi. BiCarbonate availability had significant and rapid effects on pHi in exponential- but not in stationary-phase cells. 4′, 4′-Diisothiocyanostilbene-2,2′-disulfonic acid did not block biCarbonate uptake from the external medium by exponential-phase cells. Inorganic Carbon utilization by exponential- and stationary-phase cells of Emiliania huxleyi was investigated using a pH drift technique in a closed system. Light-dependent alkalization of the medium by stationary-phase cells resulted in a final pH of 10.1 and was inhibited by dextran-bound sulphonamide, an inhibitor of external Carbonic anhydrase. Exponential-phase cells did not generate a pH drift. Overall, the results suggest that for high-calcifying cultures of E. huxleyi the predominant pathway of Inorganic Carbon utilization differs in exponential and stationary phase cells of the same culture.
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Calcification and utilization of Inorganic Carbon by the coccolithophorid Emiliania huxleyi Lohmann
New Phytologist, 1992Co-Authors: N. A. Nimer, M. J. MerrettAbstract:summary The relationship between Inorganic-Carbon dependent photosynthetic oxygen evolution and calcification was investigated in high- and low-calcifying strains of Emiliania huxleyi showing a ten-fold difference in calcification rate. Unlike the low-calcifying strain calcifying cultures showed a four-fold increase in Inorganic Carbon (1 mM) dependent photosynthetic oxygen over the pH range 5-8.3 resulting in a 20 fold difference in photosynthetic rate between the two strains at pH 8.3. Calcifying cells have a high affinity for HCO3−, the concentration of dissolved Inorganic Carbon [DIC] required for half-maximal rate of photosynthetic O2 evolution (K0.5[DIC]) being 200 μM at pH 8-3. In mid-exponential phase cultures the stoichiometry between 14CO2 fixation and calcification was 1 : 1 so it is likely that the high photosynthetic rate at pH 8.3 is sustained by 14CO2, released from H 14CO2 during calcification. Measurement of biCarbonate transport by the silicone-oil-layer centrifugal filtering technique demonstrated a rapid uptake and achievement of equilibrium (less than 3 s) between the intracellular and external Inorganic Carbon concentrations in low and high-calcifying cells. Subsequent metabolism of the 14C intracellular Inorganic Carbon pool did not occur in low-calcifying cells suggesting the block in calcification occurs either in transport into or within the coccolith vesicle.
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Inorganic Carbon transport in some marine microalgal species
Canadian Journal of Botany, 1991Co-Authors: M. J. MerrettAbstract: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...