Table 2. btuE expression results in decreased intracellular ROS.

	Fluorescence (AU/mg protein×103)
E. coli strain	Control	K2TeO3	Paraquat	K2CrO4
BW25113 pBAD	14.6±0.8	26.5±0.8	22.0±1.7	96.1±3.0
BW25113 pBAD/btuE	10.0±1.2	20.0±1.2	12.7±2.2	47.2±2.8
ΔbtuE pBAD	19.1±2.2	26.5±0.8	23.1±0.9	95.0±3.1
ΔbtuE pBAD/btuE	10.1±1.0	20.8±0.7	13.4±2.4	48.3±1.8

Cytoplasmic ROS content was assessed by measuring the activation of 2′,7′-dihydrodichlorofluorescein diacetate in wild type, pBAD/btuE, ΔbtuE and ΔbtuE pBAD/btuE cells as described in Methods. Cells were induced with 0.2% arabinose and exposed to K₂TeO₃ (0.5 µg ml⁻¹), paraquat (50 µg ml⁻¹) or K₂CrO₄ (1 mM) for 15 min at 37°C. Fluorescence (AU, arbitrary units) was determined and normalized per mg of protein. Values represent the mean of three independent trials ± SD.