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Calcification and utilization of inorganic carbon by the coccolithophorid Emiliania huxleyi Lohmann.

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Bibliographic Details
Title: Calcification and utilization of inorganic carbon by the coccolithophorid Emiliania huxleyi Lohmann.
Authors: Nimer, N. A.1, Merrett, M. J.1
Source: New Phytologist. Jun92, Vol. 121 Issue 2, p173-177. 5p.
Subjects: Carbon, Light elements, Photosynthetic oxygen evolution, Cells, Metabolism, Biology
Abstract: 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 [DICJ 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 11CO2 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 14CO3 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. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:The relationship between inorganic-carbon dependent photosynthetic oxygen evolution and calcification was investigated in high- and low-calcifying strains of <em>Emiliania huxleyi</em> 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 [DICJ 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 11CO2 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 14CO3 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. [ABSTRACT FROM AUTHOR]
ISSN:0028646X
DOI:10.1111/j.1469-8137.1992.tb01102.x