Amino Acids and Growth Factors in a Chemi-Cally Defined Medium for Drosophila

Abstract

Studies were made of various amino acids and growth factors using a chemically defined medium in the absence of microorganisms, attempting to perfect the medium so that normal development of Drosophila could be obtained. A medium is presented which is completely chemically defined except for agar and which allows normal development of nearly 100% of the eggs to the adult condition with pupation occurring in 6-7 days (only 1-2 days slower than the normal). The studies suggest that the normal rate of development can be achieved by finding the proper balance of nutrilites, rather than locating unidentified growth factors, since various yeast fractions added to a complete medium failed to improve development. Data are presented to show the effect on development of various concns. of the following substances: tryptophan, isoleucine, serine, glycine, arginine, citrulline, ornithine, biotin, pyridoxine, lecithin, vit. B12, protogen, vit. Bt, inositol and p-aminobenzoic acid. Tryptophan, isoleucine, and serine have an inhibitory effect on growth when present in high concns., and the data suggest that high levels of ribonucleic acid act as an antagonist to the inhibition. Better results were obtained using 18 amino acids in the medium than when any other combination was used. The natural forms are generally best, although the racemic mixture gave almost as good growth in the case of some of the amino acids.