AMINO-ACID SYNTHESIS IN THE SYMBIOTIC SEA-ANEMONE AIPTASIA-PULCHELLA

Symbiotic Aiptasia pulchella and freshly isolated zooxanthellae were i ncubated in (NaHCO3)-C-14 and NH4Cl for 1 to 240 min, and samples were analysed by reverse-phase high-performance liquid chromatography (HPL C) and an online radiochemical detector. NH4+ was first assimilated in to C-14-glutamate and C-14-glutamine in the zooxanthellae residing in A. pulchella. The specific activities (dpm nmol(-1)) of C-14-glutamate and C-14-glutamine in vivo, were far greater in the zooxanthellae tha n in the host tissue, indicating that NH4+ was principally incorporate d into the glutamate and glutamine pools of the zooxanthellae. C-14-al pha-ketoglutarate was taken up from the medium by intact A. pulchella and assimilated into a small amount of C-14-glutamate in the host tiss ue, but no C-14-glutamine was detected in the host fraction. The C-14- glutamate that was synthesized was most likely produced from transamin ation reactions as opposed to the direct assimilation of NH4+. The fre e aminoacid composition of the host tissue and zooxanthellae of A. pul chella was also measured. The results presented here demonstrate that NH4+ was initially assimilated by the zooxanthellae of A. pulchella.