FIG.7.

Effect of hemin concentration on lipid A content of a P. gingivalis hemin acquisition mutant. P. gingivalis strain A7436 (A, B, and C) and its isogenic Kgp/HmuR double mutant strain WS15 (D, E, and F) were incubated in TYHK medium with various concentrations of hemin, as indicated in each panel. P. gingivalis LPS was obtained by the Tri-Reagent procedure (30), and lipid A was cleaved and separated from the LPS as described by Caroff et al. (3). MALDI-TOF analysis was performed as previously described (11). All values given are average masses rounded to the nearest whole numbers for singly charged deprotonated molecules. Note that strain WS15 required a higher concentration of hemin to alter its lipid A content.