Revised structures for the predominant O-polysaccharides expressed by Burkholderia pseudomallei and Burkholderia mallei

• B. pseudomallei and B. mallei are CDC Tier 1 select agents.
• B. thailandensis is a non-pathogenic saprophyte.
• B. pseudomallei OPS is structurally similar to B. mallei OPS.
• B. pseudomallei OPS is structurally identical to B. thailandensis OPS.
• 3-O-Methylated 6dTal residues terminate OPS chain elongation in all three species.

O-Polysaccharides (OPS) were isolated from purified Burkholderia pseudomallei and Burkholderia mallei lipopolysaccharides by mild-acid hydrolysis and gel-permeation chromatography. 1-D and 2-D 1H and 13C NMR spectroscopy experiments revealed that the OPS antigens were unbranched heteropolymers with the following structures:Collectively, our results demonstrate that the predominant OPS antigens expressed by B. pseudomallei and B. mallei isolates are structurally more complex than previously described and provide evidence that different capping residues are used by these closely related pathogens to terminate chain elongation. Additionally, they confirm that Burkholderia thailandensis and B. pseudomallei express OPS antigens that are essentially identical to one another.

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