UPTAKE OF AMINO ACIDS BY CULTURED AND FRESHLY ISOLATED SYMBIOTIC CHLORELLA

Abstract

Amino acid uptake was investigated in two cultured strains of symbiotic Chlorella sp., 3N813A and NC64A, and in Chlorella algae freshly isolated from symbiosis with the European strain of Hydra viridissima; E/E algae (the natural symbiont) and E/3N and E/NC algae (3N813A and NC64A in artificial symbiosis). Cultured 3N813A possessed at least two active uptake systems, a general system transporting proline, serine, alanine, glycine and glutamine, and one transporting arginine and lysine (although uptake of the latter was low). Unusually, arginine appeared to be transported in its neutral form, since low pH inhibited uptake. Cultured NC64A possessed only the arginine/lysine system, but in E/NC isolated from symbiosis the general system was also present. Algae freshly isolated from symbiosis showed a more active, rapidly saturated general transport system than cultured 3N813A, in which uptake was linear over a 2 h time course. Uptake of arginine was not affected by growth in symbiosis, but both E/3N and E/NC algae took up lysine at a faster rate than cultured 3N813A and NC64A. Attempts to induce higher activity of the two transport systems in cultured algae were mostly unsuccessful. Growth in nitrogen‐deficient medium reduced rather than increased uptake of proline and alanine by 3N813A, and it had no effect on lysine uptake; and although this treatment increased uptake of lysine by NC64A, neither nitrogen deficiency nor pretreatment with glucose induced the general transport system. The implications of the ability of algae symbiotic with hydra to take up amino acids are discussed with especial reference to host cell regulation of algal cell division. Copyright © 1986, Wiley Blackwell. All rights reserved