FIG 3.

Dietary methionine influences D. melanogaster SR and triglyceride content. (A) To test MGWA predictions that B vitamins and sulfur amino acids influence fruit fly SR, SR was measured in bacterium-free Canton-S flies reared on a YG diet supplemented with B vitamins, cysteine (Cys), or methionine (Met). As controls, bacterium-free flies (Ax-C) and 5-species gnotobiotic flies (5sp-C) were reared on an unsupplemented YG diet. (B) To test for interactive effects between dietary methionine supplementation and the microbiota, SR was measured in flies reared in a factorial design to compare bacterial treatment and methionine supplementation (none = no supplement; Met = 10 mM supplemented methionine). D, diet; G, genotype. (C) Triacylglyceride (TAG) contents of axenic flies reared on methionine-supplemented versus normal YG diets. Light-gray bars, axenic flies; dark-gray bars, 5-species gnotobiotic flies. Different letters over the bars represent statistically significant differences between treatments, as determined by a Cox mixed-effects survival model (A and B; for each treatment, n = triplicate vials of 10 flies in each of three separate experiments, unless a vial was discarded with contamination) or a Wilcoxon test (C, n = 4 to 5 replicates in each of 2 experiments per treatment). W, Wilcoxon test statistic.