SUBSTITUTION OF CHOLINE BY RELATED COMPOUNDS AND FURTHER STUDIES ON AMINO ACID REQUIREMENTS IN NUTRITION OF PHORMIA REGINA (MEIG.)

Abstract

Phormia regina grown on a chemically defined diet under sterile conditions has been shown to have a specific dietary requirement for choline. The present work shows that carnitine and 2,2-dimethylaminoethanol can completely replace this in the diet whereas betaine is ineffective in this respect. Deletion of single amino acids from a mixture of 18 adequate for growth has previously shown the following 10 amino acids to be essential: arginine, histidine, leucine, lysine, phenylalanine, threonine, tryptophan, valine, proline, and isoleucine. The present work: shows by the inability of the organism to grow on these essential amino acids that this method is not adequate to detect amino acid combinations for which alternate requirements exist. By the deletion of groups of two or more amino acids it has been shown that P. regina has a dietary requirement for either methionine or cystine and for either glutamic acid or aspartic acid. Growth on the 10 essential amino acids is stimulated by yeast extract. This is apparently not due to a simple replacement of missing amino acids, since the addition of yeast creates an increased requirement for thiamine.