The extent of changes in experimental evolution among the strains. (a-f) Principal components analysis (PCA) of the metabolome (panels a to c) and transcriptome (panels d to f) data; each data point represents an experimental sample plotted using the first three principal components. PCA was carried out on the log-transformed mean-centred data matrix using all identified metabolites and the genes with P ≤ 0.05 (Student's t-test) in at least one strain. Values given for each component in parentheses represents the percentage of variance. (g-l) Pair-wise correlation maps of the metabolome (panels g to i) and transcriptome (panels j to l) data among the strains, using Pearson correlation coefficient (r). All of the metabolites and the genes having a threshold value of r ≤ -0.9 or ≥ 0.9 were plotted and color coded on both axes of a matrix containing all pair-wise metabolite or gene expression profile correlation. Darker spots indicate greater degrees of negative correlation among the strains. Both the analyses were carried out using Matlab 6.5 (The MathWorks, Inc., Natick, MA, USA).