Fig. 5.

Regulatory effect of KdpDE on spa expression. (A) Analysis of the transcriptional regulation of spa by KdpDE. The transcript levels of spa were compared using real-time RT-PCR in WT, SX8 (kdpDE mutant), SX9 (kdpDE mutant with a plasmid encoding KdpDE), SX10 (kdpE mutant), and SX11 (kdpE mutant with a plasmid encoding KdpE). Three groups of strains were grown in LB medium to OD₆₀₀s of 1, 2, and 3, respectively. (B) Comparative measurements of survival rates of WT, SX8, SX9, SX10, and SX11 in heparinized human blood. Results are from five separate blood donors. (C) Comparative measurements of survival rates of WT, SX8, SX9, SX10, and SX11 when cultured with U937 monocytic cells. The percentage of S. aureus CFU that survived was determined as described in Materials and Methods. (D) Influence of K⁺ stimuli on the transcription of spa and kdpD. The transcript levels of kdpD and spa in WT were tested in cells grown under different K⁺ conditions for different times. Three groups of wild-type bacteria were cultivated in CDM with 0.2 mM, 4 mM, and 100 mM K⁺. All the real-time PCR assays were repeated four times with similar results. Error bars indicate standard deviations.