FIGURE 2.

Variation in the number of amide linkages and phosphorylation in C. jejuni LA. A, hexaacylated C. jejuni lipid A with GlcN (R = O) and/or GlcN3N (R = N) disaccharide backbone originally described in Ref. 13 and confirmed in the present study. O-Deacylated LA composed of a GlcN3N-GlcN3N disaccharide backbone with four amide-linked acyl chains (B), a GlcN-GlcN3N disaccharide backbone with three amide-linked acyl chains (C), or a GlcN-GlcN disaccharide backbone with two amide-linked acyl chains (D) is shown. The LA backbone is depicted with two phosphate and two phosphoethanolamine groups, although the abundance of these modifications can vary. Y-type reducing terminal LA fragment ions were observed as shown in the portion of the negative ion MALDI-TOF MS spectra of the O-deacylated LOS of strain 40917 (E) and 31485 (F). G, the relative abundance of amide linkages was assessed by summing the areas of peaks corresponding to four amide linkages and expressing this as a percentage of the areas of all LA peaks observed in the MS analysis. Portions of negative ion MALDI-TOF spectra of the intact lipid of strains 33106 (H) and KJCattle8 (I) in which postulated Y-type LA fragment ions were observed are shown. J, the relative abundance of LA with three or four phosphoryl groups was calculated by summing the area of peaks corresponding to LA with three or four phosphoryl moieties and expressing this as a percentage of the total area of all LA peaks observed.