FIG 6.
The B. pseudomallei pagL mutant is unable to produce tetra-acylated lipid A. (A) Negative-ion mode scan from 1,000 to 2,000 m/z of 1026b wild-type lipid A (green) compared to that of the pagL mutant (light blue). The diagram shows the simplified penta-acylated (LApenta) and triacylated (LAtri) lipid A observed. Horizontal arrows indicate −228 mass differences indicative of C14:0-OH, a −131 mass difference indicative of amino arabinose, and a −80 mass difference indicative of a phosphate group. (B) Positive-ion mode scan of the same lipid A from 900 to 1,500 m/z. (C) Cytotoxicity measurements following LPS transfection into Salmonella LPS-primed RAW264.7 murine macrophages. White bars represent no-Lipofectamine controls, and gray bars represent exactly the same treatment but with Lipofectamine. Data are the mean and standard deviation of the results of one representative experiment carried out in triplicate. Significance was determined by one-way ANOVA to 1026b wild-type LPS. **, P < 0.01; ****, P < 0.0001.