Growth curves and ROS level measurements. Characterisation of wild type R. sphaeroides (black) and the 2.4.1∆oxyR mutant (grey) was performed in oxic conditions in the presence (A) or absence (B) of iron. The optical density at 660 nm (OD660) was determined over time, and growth is indicated as continuous line. The intracellular levels of ROS (squares) are presented in arbitrary units. Both data sets represent the mean of at least three independent experiments, and the error bars indicate the standard deviation.