Figure 5

Catalase activity as potential biomarker for mild stress induced robustness. A) Unstressed B. cereus ATCC 14579 cells (uns) and mild oxidative stress treated cells (0.1 mM H₂O₂ treatment for 2 to 60 min) were exposed to 0.2 mM H₂O₂ at 30°C for 2 min to determine their robustness towards lethal oxidative stress. The columns mark the number of cells surviving the lethal treatment compared to the initial number of cells (%). B) Catalase activity was measured in unstressed cells and 0.1 mM H₂O₂-treated cells. The columns mark the induction of catalase activity after mild oxidative treatment (s) compared to unstressed cells (uns). C) The induction of catalase activity upon mild oxidative stress treatment was correlated to the induction of robustness towards lethal oxidative stress and their correlation was tested for significance. Robustness was determined as the number of cells surviving the lethal treatment, (N(t)), compared to the initial number of cells, (N(0)), and the robustness of mild oxidative stress treated cells was expressed relatively to that of unstressed cells, namely, .