Cyclic-di-AMP levels in S. aureus are not affected by inactivation of clpX or clpP. Data represent intracellular c-di-AMP concentrations. The concentrations of c-di-AMP in the cytoplasm of strains LAC*, LAC* gdpP, SA564, SA564 clpX, SA564 clpP, 564-25-2 (clpX ltaS), JE2, JE2 clpX, and JE2 clpP were determined by LC-MS/MS. Values indicate c-di-AMP levels per milligram of bacterial dry weight, and the averages and standard deviations of results from three replicates are plotted.