Fit of growth data at high induction (220 μM IPTG) using a reaction kinetics model (Additional file 1). The dotted horizontal line indicates the growth rate in the absence of Pgal and IPTG. The growth difference between this line and the data point at [Pgal] = 0 represents the cost of protein expression. For higher Pgal concentrations this cost is compensated and eventually dominated by the benefit of Pgal metabolism. Cost and benefit are balanced for a Pgal concentration of 1.2∙102 μM.