Nitroblue tetrazolium salt (NBT) assay of superoxide dismutase (SOD) activity from whole cell lysates of <i>B. anthracis</i> grown in various growth conditions.

<p>(A) Percent inhibition of superoxide production from 5 µg of whole cell lysates of <i>B. anthracis</i> Sterne 34F₂, and the mutants <i>ΔsodA1</i> and <i>ΔsodA2</i> grown in LB (iron-rich) medium with and without the addition of a high concentration of paraquat (800 µM). (B) Percent inhibition of superoxide production from 5 µg of whole cell lysates of <i>B. anthracis</i> Sterne 34F₂ grown in IDM and IDM supplemented with 20 µM Fe(II)SO₄•7H₂O under high and low aeration. Low O₂ indicates cultures grown in a 40% culture to flask volume/volume ratio with slow shaking (125 rpm); High O₂ indicates cultures grown in a 10% culture to flask volume/volume ratio with rigorous shaking (300 rpm). Percent inhibition indicates the amount by which the cell lysate inhibits NBT reduction relative to a non-lysate containing control reaction (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020777#s3" target="_blank">Materials and Methods</a>).