Measurements of culture conditions
The pH of the culture was measured using an Oakton pH 700 meter. The concentration of ferrous iron in solution was measured by titrating 1 mL of the medium with 10 µL of ferroin indicator with 0.1 M cerium (IV) sulfate until the color of the indicator changed from orange-red to a light blue. The samples were diluted with ddH2O adjusted to pH1.8 as necessary so that titrated ferrous iron was below the equivalent of 30 mM ferrous iron.