Structure of the O-antigen of the lipopolysaccharide isolated from Pantoea ananatis AEP17, a rhizobacterium associated with rice

The lipopolysaccharide of a Gram-negative bacterium having a putative plant-growth promoting activity (Pantoea ananatis AEP17) has been isolated and subjected to partial hydrolysis. The O-antigen has been studied by mass spectrometry and NMR experiments. On the basis of these experiments it is concluded that the following repeating unit is present in the polysaccharide:→3)-β-d-GlcpNAc-(1→3)[α-d-GalpAN-(1→2)]-α-l-Rhap-(1→2)-α-l-Rhap-(1→3)-α-l-Rhap-(1→2)-α-l-Rhap-(1→The occurrence of d-galacturonamide (GalAN) is unusual in bacterial O-polysaccharides. It has only been reported in Escherichia coli O65 [Perry, M. B.; MacLean, L. L. Carbohydr. Res.1999, 322, 57–66].

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► The lipopolysaccharide of a putative plant-growth promoting rhizobacterium has been isolated.
► The structure of its O-antigen has been studied by mass spectrometry and NMR.
► O-Antigen consists of the branched hexasaccharide repeating unit.
► The polysaccharide contains d-galacturonamide among other carbohydrates.