Abstract
The haptophyte alga Emiliania huxleyi possesses two carbon fixation pathways to produce organic and inorganic compounds in photosynthesis and calcification, respectively. Using a radiotracer technique, the photosynthetic primary products were determined after the incubation of cells with 2 mM NaH14CO3 for 10-120 s under the light and the labeled compounds were identified by thin-layer chromatography. The time course and the pulse-chase experiment showed that phosphate esters, mostly the Calvin-Benson (C3) cycle intermediate, and Asp were synthesized first and metabolized to lipids and amino acids such as Ala and Glu. These data showed the initial carbon fixation was driven by both the Calvin-Benson cycle and β-carboxylation reaction and then the products were immediately metabolized via TCA cycle and its associated pathway.
