FIGURE 4.

Attenuation of pyocyanin production in the P. aeruginosa MPAO1 and IA614 phuS mutants on supplementing the medium with hemoglobin. A, pyocyanin production over a 24-h growth period in the absence (dashed line) or presence (solid line) of 100 μm hemoglobin. All pyocyanin extractions were carried out on cultures of the wild-type MPAO1 and 7520 phuS::Tn mutant strains at equivalent cell densities. Data are means ± S.E. of three separate experiments. B, pyocyanin production in the 7520 phuS::Tn (black bars) and IA614-ΔphuS (gray bars) mutants as a function of hemoglobin concentration. Extraction and quantification of pyocyanin were carried out as described under “Experimental Procedures.” Data are means ± S.E. of three separate experiments. *, p < 0.001 (versus control value no exogenous hemoglobin).