The pH dependency of light production of S.
aureus RN4220/pTOO24 and RN4220/pCSS810 cells. The assay was
performed in citrate-phosphate buffer (pH range, 4.6 to 5.6 [⧫]),
MES (pH range, 5.6 to 6.6 [▪]) and MOPS (pH range, 6.6 to 7.0
[▴]) as described in Materials and Methods. Panel A shows the pH
dependency of d-luciferin penetration into the indicator
RN4220/pTOO24 cells, and Panel B shows results for strain
RN4220/pCSS810.