Figure 4

OxyR and manganese are necessary for survival upon exposure to adrenaline. The role of the major oxidative stress regulator OxyR in the ability of Salmonella spp. to survive exposure to various adrenaline concentrations was assessed. (A) Deletion of oxyR in SL1344oxyR results in a dramatic loss of viability when exposed to adrenaline (50 μM) for 30 minutes. The effect of adrenaline is significantly lessened by addition of propranolol (PO) at 500 μM. Addition of the adrenaline derivative metanephrine (50 μM) which cannot bind iron has no significant effect on cell viability. Addition of manganese (5 mM) also fully counteracts the growth inhibition observed by adrenaline while the metal by itself (Mn) does not affect survival. SL1344 viability is unaffected by adrenaline (data not shown). (B) Measurement of total cell iron indicating a significant 4-fold increase upon exposure of SL1344 to adrenaline, reduced levels upon simultaneous exposure to propranolol and adrenaline, and also significantly elevated levels in SL1344oxyR. (C) Measurement of total cell manganese indicating significantly reduced (3-fold) levels in SL1344oxyR and slightly reduced levels in SL1344 upon addition of adrenaline or simultaneous exposure to propranolol and adrenaline. Experiments were repeated at least three times. Asterisk indicates significant difference by the student t-test. Standard error bars are shown. Adrenaline, ADR; Propranolol, PO; Metanephrine, MNPH; Manganese, Mn.