Fig. 3.

Caloric restriction extends lifespan in S. pombe. (A) SD + 3% glucose is an appropriate standard condition for CLS assays. Chronological lifespans were measured in SD + 3% or 4% glucose as described in the Materials and Methods. All lifespans were performed at the same time. The lifespan of the SD + 5% glucose culture from Fig. 1A is included for comparison. The lifespans in 3% and 4% glucose were not significantly different (p = 0.28), while the 5% lifespan is significantly shorter than 3% glucose (p = 0.0005). Error bars represent the ranges of duplicate experiments. (B) CLS assays were performed and analyzed as in panel A with the glucose concentrations shown, except that the 0.3% and 0.1% cultures were sampled every two days. All lifespans were performed in duplicate and run concurrently. The 3% glucose cultures in panel B are independent from those in panel A. All lifespans for cultures with 2% glucose or less were significantly longer than the 3% glucose culture (p < 0.008). (C and D) The normalized log₁₀(CFU/ml) from the CLS experiments in panels A and B are plotted, respectively. The normalization of the log₁₀ values starts all lifespans at the same point, and allows cultures that grow to different maximum densities (e.g. the 3% and 0.1% glucose cultures) to be directly compared. (E) Median lifespans from cultures with different glucose concentrations as defined as the point where the normalized log₁₀(CFU/ml) equals 0.5. Median CLS values were calculated by linear interpolation between the values immediately above and below 0.5. The slightly different values for the two independent 3% glucose experiments performed on different days (in panels A and B) are shown.