L-Serine supplementation extends life span of NR cultures.A, CLS of nonrestricted BY4741 supplemented with 2% CRCM, 1 mM L-serine, or 5 mM L-serine. B, mean CLS statistics from panel A calculated using OASIS 2. C, CLS of nonrestricted BY4741 supplemented with 5 mM of each indicated amino acid. ∗Amino acids 1–5 significantly extended life span compared with the NR control (sample 8) (D) Mean CLS statistics from panel C calculated using OASIS 2. E, CLS of nonrestricted BY4741 supplemented with increasing concentrations of L-serine. CR indicates the glucose-restricted control samples. F, mean CLS statistics from panel E calculated using OASIS 2. G, CLS of BY4741 supplemented with increasing concentrations of D-serine. CR indicates the glucose-restricted control. H, mean CLS statistics from panel G calculated using OASIS 2. All CLS assays were run in triplicate. I, pH measurements of NR cultures supplemented with 10 mM L-serine or D-serine at the time of inoculation and then grown into stationary phase. CR is used as a positive control for suppressing hyperacidification. Individual data points are displayed for each time point.