The Effects of Folic Acid on Endosymbionts, Growth & Metabolites of the Fruit Fly Drosophila melanogaster

Folic acid is needed for nucleotide synthesis and amino acid metabolism. Its deficiency leads various diseases, but mechanisms are unclear. The fruit fly, Drosophila melanogaster , could be a model for studying folate's biomedical effects but the current literature lacks key information. We examined folic acid in relation to endosymbionts, growth, and metabolites of the fruit fly. First, we show fruit flies consuming diets lacking folic acid received sufficient folates from symbionts, allowing normal development. Second, we show body folate levels were nearly homeostatically‐regulated despite huge variation in dietary folate. When reared for a second generation on these diets, larvae on the very low folate diets were also more viable and retained faster developmental rates, also seen in the first generation. Third, we show folate is needed for DNA synthesis in fruit flies, but not for some single‐carbon cycle reactions for which it is needed in mammals. Thus, folate functions in fruit flies overlap with mammals, but endosymbionts allow fruit flies to fare better when dietary folic acid is low, and flies may have additional metabolic pathways to accomplish functions that in mammals use folate.