Table 1.
Internal standards that were spiked into E. faecalis lipid extracts.
Fig 1.
Precursor ion scans for Enterococcus faecalis phospholipids.
Precursor ion scans for (A) 153 fragment ion (phosphatidylglycerol (PG))) and (B) 145 fragment ion (lysyl-phosphatidylglycerol (LPG)) reveal several species of PG (A) and of LPG (B). Each peak is labelled with the class (PG or LPG), fatty acid composition (e.g. 34:1), and the mass-to-charge (m/z) ratio (e.g. 747.6 for PG 34:1).
Fig 2.
The diversity of lipid species in E. faecalis strain OG1RF.
(a) The total number of lipid species identified is 63 across 7 classes. Representative MSMS spectra for the phospholipids (PG, lysyl-PG, and cardiolipin (CL)) are shown for (b) PG 34:1, (c) lysyl-PG 34:1, and (d) CL 68:2. Each species is identified based upon its characteristic fragmentation pattern: MSMS of (b) PG 34:1 gives rise the glycerol-phosphate headgroup (m/z = 153) and fatty acids 16:0 (m/z = 255.3) and 18:1 (m/z = 281.3); (c) lysyl-PG 34:1 gives rise to lysine (m/z = 145) and fatty acids 16:0 and 18:1; and CL (68:2) gives rise to the glycerol-phosphate headgroup and fatty acids 16:0 and 18:1.
Fig 3.
The levels of E. faecalis strain OG1RF PG and LPG can be tracked throughout the growth curve.
(A) Heat map depicting phosphatidylglycerol (PG) and lysyl-PG levels in the early-, middle- and late-logarithmic growth phases relative to the late stationary phase. The colour scale (top right) indicates fold change of phospholipids (PG and lysyl-PG) in early-, mid-, and late-logarithmic phase cells with respect to late stationary phase cells. (B) Bar chart showing representative fold change values for PG 34:0, 34:1 and 34:2. (C) The three logarithmic phases corresponded to optical density (OD) values of 0.3, 0.5 and 0.8 on an OD growth curve.
Table 2.
Single Nucleotide Polymorphisms (SNPs) in the DapR strains Dap21 and Dap22.
Table 3.
Minimum Inhibitory Concentrations (MICs) of daptomycin for three E. faecalis strains.
Fig 4.
The levels of PG and LPG in two daptomycin-resistant strains, Dap21 to Dap22, compared to non-resistant OG1RF.
The bar chart shows the fold change of 5 LPGs and their corresponding PGs from Dap21 and Dap22 grown to mid-logarithmic phase, with respect to the non-resistant OG1RF parental strain. Data are expressed as mean ± standard deviation (SD) (calculated from 5 replicates) with the SDs represented as error bars.
Table 4.
Previous biochemical analyses of Enterococcus faecalis compared to the present study.