Structural studies on the short-chain lipopolysaccharide of Vibrio cholerae O139 Bengal

Abstract

A Vibrio cholerae O139 strain, MO10-T4, lacking capsular polysaccharide, produces a short chain lipopolysaccharide (LPS), similar to enterobacterial SR strains. It was studied by acidic and alkaline degradation, dephosphorylation, sugar and methylation analysis, high-performance anion- exchange chromatography, one- and two-dimensional 1H-, 13C- and 31P-NMR spectroscopy, and electrospray ionization mass spectrometry. An O-acetyl group is present on a secondary position, tentatively O4 of the α-linked glucosyl group. Some LPS species contain an additional putative fructose residue whose location remains unknown. An O139-negative mutant strain, Bengal-2R, derived from V. cholerae O139, has also been investigated and shown to produce an O-antigen-lacking LPS similar to those from enterobacterial R strains, some of the LPS species containing the same core region as the strain MO10-T4 LPS and the other lacking the lateral heptose residue. The carbohydrate backbone core structure is the same for the V. cholerae O139 and V. cholerae O1 LPS, thus confirming the close relation between these bacteria; however, the 2-aminoethyl phosphate, the O-acetyl group, and the second fructose residue have not been reported for the O1 LPS. In the V. cholerae O139 strain MO10T4 LPS, a short O-side chain is attached at position 3 of the 7-substituted heptose residue and has the same structure as one repeating unit of the V. cholerae O139 capsular polysaccharide. Some details of the structure proposed are at variance with those recently published for another V. cholerae O139 strain [Cox, A.D., Brisson, J.-R., Varma, V. and Perry, M. B. (1996) Carbohydr. Res. 290, 43-58; Cox A. D. and Perry, M. B. (1996) Carbohydr. Res. 290, 59-65].