Abstract:
Since the early days of genetic research, Drosophila culture medium has been routinely supplemented with baker's yeast (Saccharomyces cerevisiae) and brewer's yeast (Saccharomyces carlsbergensis) to provide nutrients not provided by other components of the medium. The purpose of this study was to learn more about the specific roles of these two yeasts in supporting the growth of Drosophila. In the traditional way of preparing fly food, brewer's yeast is mixed in with the other ingredients before cooking and baker's yeast is sprinkled on top of the medium after cooking and cooling. This study investigated 1) the effects of reversing the positions of the two yeasts and of using only one of the yeasts at a time; 2) the effect of varying the amount of baker's yeast added; and 3) the effect of adding chemically well-defined supplements in place of the two yeasts. The chemicals tested included nucleotides, nucleosides, ATP and standard vitamins. The overall study showed that over a short span, baker's yeast alone was as effective in supporting Drosophila development as the standard supplement which uses both brewer's and baker's yeasts. The best chemically-defined substitute for the two yeasts contained five nucleosides plus ATP plus a standard vitamin mixture. Addition of purine bases alone resulted in delayed reproduction and smaller numbers of offspring.Yeast.
