FIG 7.

Intracellular heme measurements. (A) Hemochrome assay. Absorbance-based measurement of WT MPAO1 or MPAO1 with clean deletions (not harboring the biosensor) of phuUV, phuR, hemO, PA0028, PA0149, dnr (PA0527), and ABM domain genes PA0709 and PA3390 following 14 h of growth in M9 plus 5 μM heme. Cells were lysed, and heme levels were determined by pyridine hemochrome and expressed relative to WT (57). (B) Fluorescent heme assay. Cells were grown as described for panel A, and the heme levels were determined as described in the legend for Fig. 1G and in Materials and Methods (30). The horizontal lines indicate the medians from five biological repeats. Individual data points are plotted. Statistically significant differences were determined using a one-sample t test with Wilcoxon test. *, P < 0.05. **, P < 0.01.