Quantification of cellular heme levels of the heme oxygenase strains compared to the strain lacking heme oxygenase activity (ΔisdGI plgt). The ΔisdGI plgt.isdI (dark grey, solid) strains contain significantly less heme than ΔisdGI plgt (black) and ΔisdGI pisd.isdI (dark grey, dashed) strains. Additionally, the ΔisdGI plgt.isdG (light grey, solid) strain contains significantly less heme than ΔisdGI plgt (1-way ANOVA, p<0.05), error bars represent S.E.M..