H₂S is the determinant of cbs expression promoting catalase activity.

Catalase activity in crude extracts of Δcbs strains containing vectors (cbs^-sqr^-; CBS^-H₂S^-), P_tac-cbs (cbs⁺sqr^-; CBS⁺H₂S⁺) only, or both of P_tac-cbs and P_BAD-sqr (cbs⁺sqr⁺; CBS⁺H₂S^-). Cells were grown in M9 minimal medium (M9 salts plus 2 mM MgSO₄, 0.1 mM CaCl₂ and 0.2% casein acid hydrolysate), containing 200 μM of IPTG and 0.02% arabinose, and treated with or without H₂O₂ (1 mM, 20 min) at their mid-log phase. Three individual experiments were taken. Significance was determined by one-way ANOVA; p-value: *, <0.05, **, <0.01, ***, <0.001.

(PDF)