Challenge of yeast cells with sublethal doses of a stressor activites stress-response signaling pathways to make cells more resistant to the stressor, a phenomenon known as adaptation. Izawa et al. pre-challenged wild-type YPH250 cells in YPD with 0.2mM H2O2, a sublethal concentration, and observed increased resistance to higher H2O2 levels. This is consistent with the results in Fig2, which demonstrates that exposure of wild-type YPH250 cells to 0.2mM H2O2 in YPD results in an 8-fold increase in catalase activity. However, catalase upregulation is negligible in KPi so pre-challenge with a low dose of H2O2 in KPi should not protect cells against a subsequent challenge with a lethal H2O2 dose whereas pre-challenge in YPD should be protective.