<p>(A) Chronological aging of methionine prototroph (MET<sup>+</sup>), semi-auxotroph (Δ<i>met15</i>) and auxotroph (Δ<i>met2</i>) isogenic yeast strains in SCD media supplemented with all amino acids (aa). Cell survival was estimated as colony formation of 500 cells plated at given time points, normalized to cell survival on day one (n = 4). (B) Chronological aging of Δ<i>met15</i> strain, in SCD media supplemented with all aa except for methionine which was added at given concentrations. Cell survival of 500 cells plated at given time points, normalized to cell survival on day one (n = 4). (C) <i>MET2</i> deletion strain (Δ<i>met2</i>) was grown to stationary phase in SCD (supplemented with all aa) and shifted to SCD media with different methionine concentrations. Cell survival of 500 cells plated at given time points, normalized to cell survival before the shift (n = 4). (D) Day 8 from experiment shown in C (n = 4). (E) Chronological aging of EUROSCARF BY4741 (also used above as Δ<i>met15</i> reference strain) and mating type α wild type strain BY4742, as well as a methionine semi-auxotrophic variant thereof (BY4742 Δ<i>met15</i>), in SCD media supplemented with all aa. Cell survival of 500 cells plated at given time points, normalized to cell survival on day one (n = 3). See also <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004347#pgen.1004347.s001" target="_blank">Figure S1</a>.</p
