Figure 2. Lysine harvest in Saccharomyces cerevisiae.

a, Lysine concentrations in wild-type and Δtpo1 yeast grown in synthetic media supplemented with or without lysine (25 μg ml^-1). The cells were grown until the mid-log phase and analysed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) (mean ± s.d.; n = 4 biologically independent samples except for Δtpo1, for which n = 3). Unpaired two-tailed Student’s t-test versus the non-supplemented control: **P = 0.0056 for wild-type and P = 0.0022 for Δtpo1. b, Harvesting to reach extreme concentrations is specific for lysine. Amino acid concentrations in wild-type yeast grown in synthetical minimal (SM) media supplemented with individual amino acids (left) or rich media (yeast extract; right) plotted as fold change compared to the average profile of seven replicates in unsupplemented synthetic media (mean ± s.d., n = 4 biologically independent samples). c, Quantification of extracellular lysine during the growth of prototrophic (LYS2) and auxotrophic (Δlys2) yeast in SM media supplemented with lysine (SM+Lys) or synthetic complete media (SC). Cultures were initiated with an OD_600nm of 0.125 and grown for 30 h. Samples were taken every 3 h, collected and the supernatant was used for quantification. Mean ± s.d.; n = 4 biologically independent samples.