scholarly journals Carbon acquisition mechanisms by planktonic desmids and their link to ecological distribution

2005 ◽  
Vol 83 (7) ◽  
pp. 850-858 ◽  
Author(s):  
Elly Spijkerman ◽  
Stephen C Maberly ◽  
Peter FM Coesel
Keyword(s):  
Distribution Pattern ◽  
Inorganic Carbon ◽  
Carbonic Anhydrase Activity ◽  
Ecological Distribution ◽  
Uptake Mechanism ◽  
Uptake Pattern ◽  
Isolate Variation ◽  
Uptake Mechanisms ◽  
Specific Inhibitors ◽  
Alkaline Waters

To test if different inorganic carbon (Ci) uptake mechanisms underlie the ecological distribution pattern of planktonic desmids, we performed pH-drift experiments with 12 strains, belonging to seven species, originating from lakes of different pH. Staurastrum brachiatum Ralfs and Staurodesmus cuspidatus (Ralfs) Teil. var. curvatus (W. West) Teil., species confined to acidic, soft water habitats, showed remarkably different behavior in the pH drift experiments: S. brachiatum appeared to use CO2 only, whereas Staurodesmus cuspidatus appeared to use HCO3– as well. Staurastrum chaetoceras (Schr.) Smith and Staurastrum planctonicum Teil, species well-known for their abundant occurrence in alkaline waters, were the most effective at using HCO3–. Other species, to be encountered in both slightly acidic and slightly alkaline waters, took an intermediate position. Experiments using specific inhibitors suggested that Cosmarium abbreviatum Rac. var. planctonicum W. & G.S. West and S. brachiatum use CO2 by an active CO2 uptake mechanism, whereas S. chaetoceras and Staurodesmus cuspidatus showed an active HCO3– uptake pattern. Most likely, these active uptake mechanisms make use of H+-ATPase, as none of the desmids expressed significant carbonic anhydrase activity. A series of strains of Staurastrum planctonicum isolated from different habitats, all clustered in between the species using HCO3–, but no further differentiation was observed. Therefore, desmids cannot be simply characterized as exclusive CO2 users, and the ecological distribution pattern of a desmid species does not unequivocally link to a certain Ci uptake mechanism. Nevertheless, there does appear to be a general ecological link between a species' Ci uptake mechanism and its ecological distribution.Key words: pH drift, desmids, isolate variation, inorganic carbon acquisition.

Fractionation of carbonic anhydrase activity in Gracilaria sp. (Rhodophyta) and Enteromorpha intestinalis (Chlorophyta): changes in the extracellular activity in response to inorganic carbon levels

2000 ◽  
Vol 27 (12) ◽  
pp. 1161 ◽  
Author(s):  
Jesús R. Andría ◽  
Juan J. Vergara ◽  
J. Lucas Pérez-Lloréns
Keyword(s):  
Carbonic Anhydrase ◽  
Inorganic Carbon ◽  
Soluble Fraction ◽  
Total Activity ◽  
Carbonic Anhydrase Activity ◽  
Enteromorpha Intestinalis ◽  
Short Term ◽  
Carbon Availability ◽  
Species Specific ◽  
Extracellular Activity

The presence of different carbonic anhydrase (EC 4.2.1.1) activities has been investigated in the intertidal macroalgae Gracilaria sp. and Enteromorpha intestinalis (L.) Nees by using fractionation techniques. Activities, measured potentiometrically, were recorded for all fractions in both species, including those containing proteins associated with chloroplast membranes. In Gracilaria sp., most of the total activity was present in the soluble fraction, while similar activities were obtained for all fractions in E. intestinalis. By using inhibitors with a different capacity to enter the cell (acetazolamide and 6-ethoxyzolamide, inhibitors of external and total activity, respectively), a surface-accessible location was indicated for a high proportion of the soluble activity obtained in Gracilaria sp. In E. intestinalis, the inhibitor assays showed a substantial dependence of photosynthesis on intracellular activity. The short-term regulation of the extracellular activity in response to inorganic carbon availability was also examined in both macroalgae. Rapid repression (after 2 h) of the activity was recorded when Gracilaria sp. was transferred from limited to replete carbon conditions, while a fairly constant activity was recorded for E. intestinalis. In contrast, an increase of external activity was obtained for both macroalgae after being transferred to carbon-limited conditions, this response being more pronounced in E. intestinalis. Our results suggest the occurrence of a species-specific carbonic anhydrase system.

Studies on the carbonic anhydrase activity in Synechocystis PCC6803 wild type and an acetazolamide-resistant mutant

1991 ◽  
Vol 69 (5) ◽  
pp. 1103-1108 ◽  
Author(s):  
S. Bedu ◽  
F. Joset
Keyword(s):  
Carbonic Anhydrase ◽  
Inorganic Carbon ◽  
Physiological Role ◽  
Resistant Mutant ◽  
Carbonic Anhydrase Activity ◽  
Wild Type ◽  
Synechocystis Pcc6803 ◽  
Physiological Analysis ◽  
Carbon Concentrations

The problem of the role and the localization of carbonic anhydrase activity in cyanobacteria has been addressed by two approaches using strain Synechocystis PCC6803. Physiological analysis of the differential effects of carbonic anhydrase inhibitors on the entry and accumulation of CO2 in cells grown under low or high inorganic carbon concentrations and determination of carbonic anhydrase activities in cellular subfractions led to the hypothesis of the presence of two different enzymes in this strain. This conclusion is compatible with current models. Only the internal enzyme could be regulated by variations of the external inorganic carbon concentrations. A parallel analysis of a mutant of this strain resistant to the inhibitor acetazolamide supported the hypothesis of the presence of two enzymes. This clone would be selectively impaired in the carbonic anhydrase activity involved in the maintenance of the internal CO2 pool, while its transport capacity is unchanged. Key words: carbonic anhydrase, physiological role, localization, inhibitors, cyanobacteria, mutant.

THE ACQUISITION OF INORGANIC CARBON IN MARINE MACROPHYTES

1998 ◽  
Vol 46 (2) ◽  
pp. 83-87 ◽  
Author(s):  
Sven Beer
Keyword(s):  
Carbonic Anhydrase ◽  
Aquatic Plants ◽  
Inorganic Carbon ◽  
External Medium ◽  
Uptake Mechanism ◽  
Tropical Regions ◽  
Marine Macrophytes ◽  
Photosynthetic Carbon ◽  
Diffusion Rates ◽  
Carbon Transport

The low diffusion rates of solutes in water call for a separation of photosynthetic carbon acquirement in aquatic plants into carbon transport and the subsequent photosynthetic reduction of CO2. This paper will focus on the transport of inorganic carbon from the external medium to the site of fixation in marine macrophytes. In accord with the much higher concentration of HCO3− than of CO2 in seawater, most marine macrophytes can utilize the ionic carbon form for their photosynthetic needs. The two known ways of HCO, utilization are (a) via extracellular, carbonic anhydrase catalyzed dehydration of HCO3− to form CO2, which then diffuses into the photosynthesizing cells, and (b) by direct uptake via a transporter. While the first way may be sufficient to support low rates of photosynthesis in temperate regions, it is viewed as futile under situations where high temperatures and irradiances would cause a high pH to form close to the uptake site of carbon and where, consequently, the CO2/HCO3− ratio would be very low. Therefore, it may well be that the direct HCO3− uptake mechanism described for Ulva from more tropical regions confers an adaptational advantage under conditions conducive to higher photosynthetic rates.

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.

Multitracer study on the uptake mechanism of yttrium and rare earth elements by autumn fern

2002 ◽  
Vol 90 (5) ◽  
Author(s):  
Takuo Ozaki ◽  
Shizuko Ambe ◽  
S. Enomoto ◽  
Y. Minai ◽  
S. Yoshida ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Plant Species ◽  
Ionic Radius ◽  
High Uptake ◽  
Uptake Mechanism ◽  
Chelating Reagents ◽  
Uptake Mechanisms

SummaryIrrespective of low bioavailability, some plant species accumulate Y and rare earth elements (REEs) to a great extent (accumulator species). The uptake mechanisms of Y and REEs were investigated for autumn fern, one of accumulator species. For comparison, plant species which accumulated poorly REEs (non-accumulator species) were also studied. In the present investigation, two noticeable phenomena were observed. (I) Autumn fern showed no ionic-radius dependence of Y-REE uptake by leaves, while non-accumulator species showed an extremely high uptake for Y compared with REEs. (II) Y-REE uptake by autumn fern was influenced by the addition of chelating reagents to the uptake solution, while no effect was observed for non-accumulator species.

The diversity of inorganic carbon acquisition mechanisms in eukaryotic microalgae

2002 ◽  
Vol 29 (3) ◽  
pp. 261 ◽  
Author(s):  
Brian Colman ◽  
I. Emma Huertas ◽  
Shabana Bhatti ◽  
Jeffrey S. Dason
Keyword(s):  
Active Transport ◽  
Active Site ◽  
Inorganic Carbon ◽  
Algal Species ◽  
Isochrysis Galbana ◽  
Co2 Uptake ◽  
Ecological Distribution ◽  
Aquatic Medium ◽  
Low Co2 ◽  
Marine Dinoflagellates

Eukaryotic microalgae have developed CO2concentrating mechanisms to maximise the concentration of CO2 at the active site of Rubisco in response to the low CO2 concentrations in the external aquatic medium. In these organisms, the modes of inorganic carbon (Ci) uptake are diverse, ranging from diffusive CO2 uptake to the active transport of HCO3 -and CO2 and many have an external carbonic anhydrase to facilitate HCO3- use. There is unequivocal evidence for the mechanisms of Ci uptake in only about 25 species of microalgae of the chlorophyte, haptophyte, rhodophyte, diatom, and eustigmatophyte groups. Most of these species take up both CO2 and HCO3-, but the rates of uptake of each of these substrates varies with the algal species. A few species take up only one of the two forms of Ci, an adaptation that is not necessarily correlated with their ecological distribution. Evidence is presented for the active uptake of HCO3- and CO2 in two marine haptophytes,Isochrysis galbana Parke and Dicrateria inornata Parke, and for active transport of CO2 but lack of HCO3- uptake in two marine dinoflagellates, Amphidinium carteraeHulburt and Heterocapsa oceanica Stein.

scholarly journals Two distinct uptake mechanisms for ascorbate and dehydroascorbate in human lymphoblasts and their interaction with glucose

1997 ◽  
Vol 324 (1) ◽  
pp. 225-230 ◽  
Author(s):  
Fook C. NGKEEKWONG ◽  
Leong L. NG
Keyword(s):  
Ascorbic Acid ◽  
Phorbol Esters ◽  
Competitive Inhibition ◽  
Dehydroascorbic Acid ◽  
Lymphoid Cells ◽  
Uptake Mechanism ◽  
Spare Capacity ◽  
Glucose Levels ◽  
Extracellular Glucose ◽  
Uptake Mechanisms

In diabetes, a major cause of mortality is from cardiovascular causes, and low levels of antioxidants such as vitamin C have been associated with such complications. Leucocyte ascorbic acid status can reflect total body stores but the mechanisms that mediate the uptake of ascorbic acid (AA) or dehydroascorbic acid (DHA) in human lymphoid cells are undefined. We have investigated the uptake of AA and DHA with mass assays in human lymphoblasts by using HPLC, with precautions to prevent the oxidation of AA and to take into account the instability of DHA in buffers. Human lymphoblasts exhibit distinct uptake mechanisms for both AA and DHA, with Vmax values of 1.35±0.14 and 29.0±5.8 nmol/h per 106 cells and Km values of 23.5±6 and 104±84 μM respectively. The AA uptake was Na+-dependent and inhibitable with ouabain, whereas DHA uptake was independent of Na+ and ouabain-insensitive. Both uptake mechanisms were inhibited by phloretin or cytochalasin B. AA uptake was decreased significantly (by 13±2%) only at extracellular glucose concentrations of 20 mM (P < 0.05). In contrast, glucose competitively inhibited DHA uptake with a Ki of 2.2 mM so that DHA uptake was decreased by glucose even in the physiological range. Phorbol esters stimulated AA but not DHA uptake; this was abolished in the presence of extracellular reductant, indicating that AA was converted to DHA before uptake occurred. Prolonged increased glucose levels (20 mM) led to a decrease in the Vmax of DHA uptake. At concentrations of plasma AA or DHA, the AA uptake mechanism might be nearly half-saturated but the DHA mechanism has enormous spare capacity. This allows for cellular uptake and regeneration of AA from DHA derived from oxidative stress. In diabetes, high glucose levels might impair DHA uptake acutely by competitive inhibition or by down-regulation of uptake with chronic glucose exposure, leading to an impaired ability to store and recycle oxidized AA.

Uptake Mechanism of Interstitially Injected 99mTc-Labeled Antimony Trisulphide Colloid in the Popliteal Lymph Node of Rabbits

1985 ◽  
Vol 24 (01) ◽  
pp. 39-43
Author(s):  
R. Senekowitsch ◽  
J. M. Sessler ◽  
S. Möllenstädt ◽  
H. Kriegel ◽  
G. Hör ◽  
...  
Keyword(s):  
Lymph Node ◽  
Distribution Pattern ◽  
Polymorphonuclear Leukocytes ◽  
Popliteal Lymph Node ◽  
Uptake Mechanism ◽  
Draining Lymph Node ◽  
Lymph Node Sinus ◽  
The Right ◽  
Medullary Cords ◽  
Radioactivity Distribution

SummaryThe right popliteal lymph node was studied in rabbits by well counting, histoautoradiography and electron microscopy, after interstitial injection of 99mTc-labeled antimony trisulphide (Sb2S3) colloid into the right hind pad. The highest radioactivity concentration (96.8%/g) was measured 6 hr following injection. At 24 hr, the concentration had dropped to nearly half of the maximum (51.5%/g). At each time, only a single or a few lymph node sectors were found to contain 99mTc. Initially, the radioactivity distribution pattern in the draining lymph node was stripy. Beginning at 15 min p.i., there was a progressive change from stripy to focal radioactivity distribution pattern. Until 6 hr after injection, the bulk of radioactivity was trapped by macrophages in the lumen and wall of the lymph node sinus system, predominantly in medullary sinuses. Surprisingly, at 24 hr the majority of labeled cells were eosinophilic polymorphonuclear leukocytes located in medullary sinuses and medullary cords. Up to 24 hr p. i., no accumulation of radioactivity could be detected in the cortical and paracortical lymph node parenchyma. In conclusion, interstitially injected 99mTc-Sb2S3 colloid is not homogeneously draining lymph node. Moreover, both macrophages and eosinophilic polymorphonuclear leukocytes are involved in the filtration process

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