Identification of the methyl phosphate substituent at the non-reducing terminal mannose residue of the O-specific polysaccharides of Klebsiella pneumoniae O3, Hafnia alvei PCM 1223 and Escherichia coli 09/09a LPS

O-specific polysaccharides of Gram-negative bacteria are synthesized by two different mechanisms: polymerization of the pre-formed O-repeating unit or sequential addition of the monosaccharides to the growing polysaccharide chain. In the second case, growth of the polymer can be further subdivided into two groups depending on the presence or absence of a special monosaccharide or non-sugar substituent that terminates the glycan. A family of polymannose O-polysaccharides provides prototypes for the chain terminating process. Polysaccharides of Klebsiella pneumoniae 03, Hafnia alvei PCM 1223, and Escherichia coli 09 have the same penta-mannose repeating unit. E. coli 09a has tetra-mannose repeat and this structure can be produced by mutants of E. coli 09. The mechanism of biosynthesis of H. alvei 1223 O-polysaccharide has not been reported. Here we show that all above polysaccharides contain the same modification at the non-reducing end; presence of a methyl phosphate group at 0-3 of alpha-mannopyranose, that serves as the signal for termination of the chain elongation. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.