Fig. 3: Structure and biosynthetic enzymes of the E. coli K-12 core oligosaccharide.

Numbers represent bond positions between sugars. Note that nonstoichiometric modifications are not shown. All linkages are α-anomeric unless preceded by the β symbol, which specifies the β-anomeric state. Enzyme names are boxed, with arrows indicating the linkages they catalyze. It is worth noting that, while the O-antigen ligation site is indicated, E. coli K-12 does not typically produce O antigen due to an ancestral mutation that inactivates its synthesis.