INORGANIC CARBON AND ACETATE ASSIMILATION IN BOTRYOCOCCUS BRAUNII(CHLOROPHYTA)1

Abstract

ABSTRACTAssimilation of 14CO2 or 14C‐acetate by the hydrocarbon producing alga Botryococcus braunii Kützing was investigated to determine the allocation of incorporated 14C among early metabolites of photosynthesis and secondary metabolites. When the cells were exposed to NaH14CO3 for 10 sec, over 90% of incorporated 14C was detected in phosphoglycerate, suggesting that this alga assimilates inorganic carbon by the C‐3 pathway. The distribution pattern of 14C in the number of metabolites revealed that organic acids, neutral sugars and amino acids were first labelled with 14C, and, after lag periods of a few minutes, lipids including hydrocarbon were increasingly labelled. Addition of 5 mM acetate to the culture medium did not affect the growth of this alga but enhanced cellular respiration. The incorporation of 14CO2 into the lipid fraction was stimulated, but net photosynthesis was inhibited by the addition of acetate. 14C‐acetate was incorporated into lipids at a very low rate in comparison with the rate of 14CO2 incorporation.