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The molecular architecture of lipopolysaccharide (LPS) isolated from all O serotypes of Vibrio parahaemolyticus was investigated. In gel chromatography on a Sephadex G-50 column, the degraded polysaccharide fraction prepared from each serotype LPS by mild acid hydrolysis yielded only core oligosaccharide (Frc II) and monosaccharide (Frc III) fractions, but no fraction (Frc I) corresponding to O polysaccharide chain consisting of polymeric repeating oligosaccharide units. Compositional sugar analysis of Frc II and III suggested that the sugar chain of LPS of all the serotypes of V. parahaemolyticus consisted of at most ten monosaccharides. Sodium dodecylsulfate-polyacrylamide gel electrophoresis of the LPS resulted in no doublet ladder band similar to that observed for S-type enterobacterial LPS. These results are compatible with the interpretation that V. parahaemolyticus O serotypes from O1 to O13 all produce R-type LPS, despite the morphologically smooth appearance, demonstrated virulence and serological O-specificity.

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A comparative study was carried out on the sugar composition of lipo-polysaccharides (LPS) isolated from representative strains of members of the family Vibrionaceae including all of the constituting genera, i.e., Vibrio, Aeromonas, Photobacterium, Plesiomonas, and Lucibacterium. More than 100 strains were examined. It was found that, with the exception of Vibrio parahaemolyticus 06, 2-keto-3-deoxyoctonate (KDO), known generally as a component sugar in the core region of usual gram-negative bacterial LPS, is virtually absent from LPS of the Vibrio-naceae strains so far examined. Furthermore, mannose was also lacking in LPS of Vibrionaceae strains with the exception of only one strain, A. anaerogenes (ATCC 15467). Instead, some KDO-like substances were found in LPS from Vibrio ("Beneckea H) nereida (ATCC 25917) and Plesiomonas shigelloides including the type strain (ATCC 14029), the same as those found in LPS from V. parahaemolyticus 07 and 012, and three strains of V. alginolyticus. These substances were strongly positive in the periodate-thiobarbituric acid test, yielding a color with maximum absorption at 549 nm. The spectra were identical to that of KDO, whereas substances differed from KDO at least in behavior in high-voltage paper electro-phoresis and thin-layer chromatography. A particularly interesting feature from the chemotaxonomical point of view was found in the sugar composition of LPS isolated from V. cholerae. Fructose was present exclusively in LPS of V. cholerae (both 01 and non-Ol groups and classical and eltor biotypes) with the exception of one strain of Photobacterium phosphoreum (NCMB 844). In addition, a pair of rarely occurring amino sugars, perosamine and quinovosamine, was found in LPS from 0 I group V. cholerae regardless of either the biotype (classical or eltor) or the serotype (Inaba or Ogawa), whereas this pair was not present in non-Ol group V. cholerae (the so-called NAG vibrios). This feature was confirmed with LPS from more than 30 additional strains of 0 I group V. cholerae isolated from patients. The virtual absence of KDO in LPS of the family Vibrionaceae was demonstrated for the first time in this study. These results are compatible with the in-649