INORGANIC CARBON TRANSPORT IN RELATION TO CULTURE AGE AND INORGANIC CARBON CONCENTRATION IN A HIGH-CALCIFYING STRAIN OF EMILIANIA-HUXLEYI (PRYMNESIOPHYCEAE)
Na. Nimer et al., INORGANIC CARBON TRANSPORT IN RELATION TO CULTURE AGE AND INORGANIC CARBON CONCENTRATION IN A HIGH-CALCIFYING STRAIN OF EMILIANIA-HUXLEYI (PRYMNESIOPHYCEAE), Journal of phycology, 32(5), 1996, pp. 813-818
The relationships among inorganic carbon transport, bicarbonate availa
bility, intracellular pH, and culture age were investigated in high-ca
lcifying cultures of Emiliania huxleyi (Lohmann) Hay & Mohler. Measure
ment of inorganic carbon transport by the silicone-oil centrifugation
technique demonstrated that gadolinium, a potential Ca2+ channel inhib
itor, blocked intracellular inorganic carbon uptake and photosynthetic
(CO2)-C-14 fixation in exponential-phase cells. In stationary-phase c
ells, the intracellular inorganic carbon concentration teas unaffected
by gadolinium. Gadolinium was also used to investigate the link betwe
en bicarbonate and Ca2+ transport in high-calcifying cells of E. huxle
yi. Bicarbonate availability had significant and rapid effects on pH(i
) in exponential- but not in stationary-phase cells. 4',4'-Diisothiocy
anostilbene-2,2'-disulfonic acid did not block bicarbonate uptake from
the external medium by exponential-phase cells. Inorganic carbon util
ization by exponential- and stationary-phase cells of Emiliania huxley
i was investigated using a pH drift technique in a closed system. Ligh
t-dependent alkalization of the medium by stationary-phase cells resul
ted in a final pH of 10.1 and was inhibited by dextran-bound sulphonam
ide, an inhibitor of external carbonic anhydrase. Exponential-phase ce
lls did not generate a pH drift. Overall, the results suggest that for
high-calcifying cultures off, huxleyi the predominant pathway of inor
ganic carbon utilization differs in exponential and stationary phase c
ells of the same culture.