FIGURE 1.

Comparison of E. coli K12 lipid A species to V. cholerae O1 and V. cholerae O139 lipid A species. The covalent modifications of lipid A are indicated with dashed bonds, and the lengths of the acyl chains are indicated below each structure. The lipid A of E. coli K12 is a hexa-acylated structure, bearing two secondary acyl chains at the 2′- and 3′-positions. The E. coli lipid A structure is glycosylated at the 6′-position with two Kdo moieties and is phosphorylated at the 1- and 4′-positions of the disaccharide backbone. Similar to E. coli, the lipid A species of V. cholerae serogroup O1 is hexa-acylated, but with a symmetrical acyl chain distribution. The proposed lipid A structure of V. cholerae O139 is the octa-acylated structure. Both V. cholerae serogroups O1 and O139 reported lipid A species have a single Kdo sugar that is phosphorylated (red) and a phosphoethanolamine (magenta) attached to the 1-phosphate.