In the SA1891 mutant (N cls2), the CL level decreased, but not completely. In the double mutant (N cls1/cls2), the CL signal was undetectable, and the phosphatidylglycerol (PG) signal was increased. Hormones antagonist This is consistent with the CL synthesis pathway. An identical result was observed in the mutants derived

from S. aureus RN4220, 8325-4, SH1000, and MT01 (data not shown). These data strongly suggest that both SA1155 and SA1891 are CL synthase genes, and thus we refer to them as cls1 and cls2, respectively. Figure 3 Lipid synthesis pathway in S. aureus (modified from the KEGG pathway database). SA1155 (cls1) and SA1891 (cls2) are homologs of the B. subtilis cls gene. Figure 4 Phospholipid composition of N315 and its isogenic cls mutants. Cells were harvested during stationary phase. The means and standard deviations of relative signal intensities are shown at the bottom. Importance of CL for long-term survival under high salinity Given that CL plays a regulatory role during cell replication and division in E. coli [28, 31, 32], we investigated

the role of the cls genes in cells during growth phase transitions Abiraterone nmr in 0.1% NaCl LB (Figure 5). Mutation of the cls genes did not affect the growth curve until 47 h (Figure 5A), after which the cls1/cls2 double mutant showed slightly lower optical density. However, stationary-phase CFU numbers did not differ significantly between the cls1/cls2 double mutant and the parent strain (Figure 5B). Moreover, the CFU numbers were sustained in both strains until at least 700 h post-inoculation (data not shown). We conclude that CL is not necessary for cell growth and stationary phase survival of S. aureus under these conditions. Figure 5 Growth and stationary-phase survival under low salinity. Cells were grown in 0.1% NaCl LB. A : Growth was monitored by optical density (OD) measurements. N315: filled diamonds; cls1 mutant: filled squares; cls2 mutant: filled triangles; cls1/cls2 double mutant: open circles. Optical densities were checked at least twice, and the means are shown. After 47 h, the OD of only N315 and its cls1/cls2 double mutant were measured.

B : Number of CFUs during Demeclocycline the long incubation. The means and standard deviations of at least three independent experiments are shown. C : Thin-layer chromatography of phospholipids. Cells were harvested at 23 h. The phospholipid profile was confirmed to be similar up to 153 h (data not shown). The means and standard deviations of relative signal intensities from two independent experiments are shown on the right. In a high-salinity medium (15% NaCl LB), the growth yield was reduced in N315 and cls mutants (Figure 6A), but the growth of cls mutants was not significantly different from that of the parent strain. In contrast, the number of cls1/cls2 double mutant CFUs was drastically reduced after ~105 to 153 h in high-salinity medium (Figure 6B).