Carotenoid was extracted from two biological replicates each of S. aureus SH1000 wildtype, ΔcspA, ΔyjbH and ΔsigB mutant strains with either pEPSA5, pALC7091 (pEPSA5::yjbH) or pALC7342 (pEPSA5::cspA) that were grown overnight on solid Tryptic Soy agar. The carotenoid levels were normalized to cell density and compared as a percentage of wildtype set at 100%. The experiments were repeated three times, with representative percentages from one experiment displayed. The asterisks indicate statistical significance between wildtype and mutant strains, determined using Student t-test (**, P < 0.005; ***, P <0.0005).