Sulfate-mediated modulation in <i>B. pertussis</i> strain B1920 (<i>ptxP1</i>) and B1917 (<i>ptxP3</i>).

<p>Sulfate was added to the culture medium to induce a high (50 mM), medium (5 mM), and low (<0.02 mM, represented as 0 mM on the x-axis) sulfate conditions. qRT-PCR data shows the relative expression level of <i>kpsT</i>, <i>bipA</i>, and <i>ptxA</i> expressed as fold changes relative to the high sulfate condition, with the values being the mean of four biological replicate cultures. Asterisks indicate a statistically significant difference between the groups as determined by Student's t-test with Welch's correction: * <i>P</i> value <0.05, ** <i>P</i> value <0.005, *** <i>P</i> value <0.0005.