Fig. 2.

KdpFABC is not a major K⁺ transporter in S. aureus. (A) Comparison of growth rates of WT, SX8 (kdpDE mutant), and SX13 (kdpFABC mutant) in CDM with different K⁺ concentrations. (B) Measurement of the internal K contents of the WT and SX13 (kdpFABC mutant) at different K⁺ concentrations of 0.2 mM, 4 mM, 20 mM, and 100 mM. (C) The regulatory effect of KdpDE on the transcription of kdpFABC in cells grown under different external K⁺ conditions. The transcript levels of kdpFABC were compared between WT, SX8 (kdpDE mutant), and SX10 (kdpE mutant) cells at different external K⁺ concentrations of 0.2 mM, 4 mM, and 100 mM. The real-time PCR assay was repeated four times with similar results. Error bars indicate standard deviations.