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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
Author(s) -
Nimer Nabil A.,
Merrett Michael J.,
Brownlee Colin
Publication year - 1996
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.0022-3646.1996.00813.x
Subject(s) - emiliania huxleyi , total inorganic carbon , bicarbonate , biology , intracellular ph , biophysics , carbonic anhydrase , biochemistry , intracellular , carbon dioxide , nutrient , phytoplankton , ecology , enzyme , endocrinology
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 Ca 2+ channel inhibitor, blocked intracellular inorganic carbon uptake and photosynthetic 14 CO 2+ 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 Ca 2+ transport in high‐calcifying cells of E. huxleyi. Bicarbonate availability had significant and rapid effects on pH i 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.