Phenotypes and gene expression profiles for “wild-type” cells.
(a) Cell density (OD at 600 nm) as a function of time for two repeated chemostat experiments with populations of “wild-type” cells deleted of HIS3. The histidine-containing medium was switched from galactose to glucose as a sole carbon source at t = 0, leaving all other nutrients the same. A steady state was first established in galactose prior to this medium switch into glucose. Note the y-axis logarithmic scale. (b) Color-coded raster plot of the mRNA expression profiles for the two populations (i and ii) as in (a). The expression levels were measured for 18 genes belonging to different metabolic functional modules (see Methods for list of genes at the same order of appearance as in the figure, starting with GFP under pGAL10 as the first gene from the bottom). The measured expression levels were normalized for each gene to zero mean and unit standard deviation across its entire time profile. The color-coded profiles are cubic-spline interpolations of the measured data points shown in Fig. 9. Bar - 10 chemostat-dilution generations.