Average expression profile of 12 expression clusters defined by hierarchical clustering. Gene expression profiles of all enzyme-coding genes in our metabolic flux model were subjected in unsupervised clustering. The number of genes in each cluster is indicated. Several clusters show a clear expression trend matching the changing physiology of the fermentation. The pink cluster is the "antibiotics" cluster, switching on upon phosphate depletion; the purple cluster includes the majority of central metabolism genes that are down-regulated.