FIG. 1.

Genetic organization of the core OS biosynthetic cluster and the structure of the core OS for E. coli K-12. (A) The waa cluster from E. coli K-12. Genes involved in inner core backbone synthesis and decorations of the inner core are shown in light grey, and genes responsible for outer core synthesis are shown in white. Genes of unknown function are highlighted in black, and waaL, involved in O-PS ligation to the core OS, is in dark gray. (B) Structure of the E. coli K-12 core OS. Dashed arrows indicate nonstoichiometric substitutions. Dotted lines identify the known or predicted genetic determinants involved in the indicated linkages.