Diauxic lag time correlates poorly with GAL gene induction kinetics but strongly with steady-state GAL gene expression in a glucose–galactose mixture.

Abstract

<p>(A) Median GAL1pr-YFP expression versus time for BC187 (blue line), YJM978 (red line), and 13 other strains (gray lines) after transfer from 2% glucose into 2% galactose. (B) Scatterplot of preparation time (from <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002041#pbio.1002041.g003" target="_blank">Fig. 3</a>) versus induction delay after glucose-to-galactose shift, defined as the time until median GAL gene expression reaches 2-fold above basal expression. Black triangle indicates strain YJM981, which did not induce above background during the entire 18-h experiment; this strain was omitted from the <i>R</i>² calculation. (C) Scatterplot of diauxic lag time (from <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002041#pbio.1002041.g001" target="_blank">Fig. 1</a>) versus induction delay after glucose-to-galactose shift. (D) Top: Schematic of how sugar concentrations for steady-state measurements were chosen from the diauxic growth experiment. Bottom: Measured steady-state GAL1pr-YFP expression distributions for BC187, YJM978, and 13 other strains in 0.0625% glucose + 0.25% galactose. (E) Scatterplot of preparation time versus mean steady-state GAL1pr-YFP expression from (D). (F) Scatterplot of diauxic lag time versus mean steady-state GAL1pr-YFP expression from (D). Dotted gray lines in (B), (C), (E), and (F) indicate least-squares linear fits used to calculate coefficients of determination (<i>R</i>²) and <i>p</i>-values. Diauxic lag time data are the mean and SEM of two replicates; preparation time and steady-state GAL1pr-YFP expression are the mean and SEM of three replicates. Induction delay after medium shift is plotted as one replicate.</p