Selective accumulation of organically bound tritium in the marine unicellular algae Dunaliella bioculata and Acetabularia mediterranea

The marine unicellular algae Dunaliella bioculata and Acetabularia mediterranea have been used to assess the importance of the radioactive contamination by ³H bound to different organic molecules. We have studied the uptake of 10 different tritiated substances, which are precursors for the cells' main macromolecules: thymidine-methyl-³H, adenine-2-³H, uridine-5-³H, L-leucine-4-³H, glycinine-2-³H, L-arginine-3.4-³H, L-aspartic acid-2.3-³H, L-phenylalanine-2.3-³H, D-glucose-2-³H and D-glucose-6-³H. Under our experimental conditions, all the tritiated organic molecules are taken up by both algal species. Their intracellular concentration may reach that of the external medium. However, some molecules are selectively a accumulated: adenine and leucine in Dunaliella, adenine, arginine and glucose in Acetabularia. Increasing concentrations of adenine and leucine, supplied to the cultures of Dunaliella, seem to be without effect on the growth of the algae.