Fig. 2.

Structural variants of lipid A of Y. pestis . (A) Tetraacyl form synthesized by wild-type strains at 37°C [11, 12, 23, 25]. One of the variants is shown; in the other variants, a diphosphate group may occur at position 4’ and Ara4N-1-phosphate at position 1; Ara4N-1-diphosphate may replace each of these groups [25]. (B) Hexaacyl form [11, 12, 20, 23] and (C) tetraacyl form [17] synthesized by wild-type strains at 20–28°C and 6°C, respectively. (D) Hexaacyl form synthesized by a recombinant strain of Y. pestis bearing the lpxL gene of Escherichia coli at37°C and 26°C [27]. Dotted lines indicate nonstoichiometric substitution.