(A) The colony diameter of S. aureus wild type, ΔisdG, ΔisdI, and ΔisdGI strains was measured after growth on solid media containing an iron chelator and various concentrations of hemin. Asterisks denote statistical significance between wild type and mutant strains, as measured by Student’s t test (p < 0.0001). (B and C) Strains listed in A were transformed with an empty vector (pOS1) or a vector expressing either isdG or isdI from a constitutive promoter (pisdG, pisdI) and colony diameter was measured as in A. A single time point at 48 hours is shown, however these trends were observed at all time points tested. Asterisks denote statistical significance between mutant and complemented strains, as measured by Student’s t test (p < 0.0001).