Arginine metabolism in Chlamydomonas reinhardi. Conditional expression of arginine-requiring mutants

Summary In Chlamydomonas reinhardi, the arginine-requiring mutants directly derived from the wild-type strain are not able to grow on media containing the routinely used concentration of ammonia. The biochemical basis of this phenomenon has been investigated.The results show that the uptake of arginine is severely depressed by NH ₊ ⁴ and that arginine which succeeds in entering the cells under these conditions is immediately broken down by the first enzyme of the catabolic pathway, arginine deiminase.Accordingly, growth is inhibited as the result of non-availability of exogenous arginine for protein synthesis.It is suggested that similar interactions could be responsible for the lack of other types of amino acid-requiring mutants in Chlamydomonas.Chargé de Recherches du Fonds National Belge de la Recherche Scientifique.