Figure 2.

(A) Pyocyanin produced by PAO1 wild-type, ∆rpoN, ΔrpoNCOM, ∆rpoN/pME6032-pqsR and ΔrpoN/pME6032 was determined by the chloroform extraction method. Means and S.D. from triplicate experiments are shown. Pyocyanin absorbance at OD_{520 nm} was normalized by culture cell density OD_{600 nm}. Student’s t-test was performed for testing differences between groups. * p ≤ 0.05; (B) Inhibition of the growth of Staphylococcus aureus 15981 by (i) PAO1; (ii) ∆rpoN; (iii) ΔrpoNCOM; and (iv) ΔrpoN/pME6032-pqsR on LB agar plates. White arrows indicate the inhibitory zones of growth.