Example of trade-offs experienced when expression is not regulated in an environment that alternates between a low Pgal concentration (39 μM) and a high Pgal concentration (500 μM). Data points denote the growth rate in each environment for a certain constant expression level (at the indicated concentrations of IPTG in μM). This trade-off data is directly obtained from Figure 1. Low expression levels (0 μM IPTG) yield optimal growth in medium with low Pgal concentrations, but non-optimal growth in medium containing high Pgal concentrations, and vice versa for high expression levels. Only when expression is regulated (low in low Pgal conditions and in high Pgal conditions), overall growth can be optimal over both environments, as is indicated by the black cross.