Fig. 1.

OPS repeat-unit structures reported from selected K. pneumoniae O-antigen serotypes. Only the sugar components are shown for O1 and “O2,” but nonstoichiometric O-acetylation can add further antigenic diversity. The polymannose OPSs possess methyl (O5) or methylphosphate (“O3”) moieties at their nonreducing termini. The OPS components are galactofuranose (Galf), galactopyranose (Galp), N-acetylglucosamine (GlcNAc), mannose (Man), methyl (Me), and phosphate (P). The chemical repeat unit structures are enclosed by parentheses.