Fig 3.

Catalase activity upon treatment with mild oxidative stress and robustness toward severe stresses for Bacillus weihenstephanensis cells precultured at 7°C. Cells were exposed to mild oxidative stress (0.05 mM H₂O₂), and catalase activity was determined before (0 min) and after treatment with mild oxidative stress for 0.25 to 4 h. Also, untreated cells and cells treated with mild oxidative stress were inactivated by exposure to severe oxidative stress (0.5 mM H₂O₂ at 30°C for 3.5 min), severe heat stress (47°C for 3 min), and severe acid stress (pH 3.7 at 30°C for 3.5 min) to quantify the effect of mild-stress treatment on robustness. The columns mark the numbers of cells that survived the severe-stress treatment compared to the initial number of cells (percent). Error bars represent standard errors of the replicates. OD, optical density.