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The structures of the capsular polysaccharides (CPSs) of the two clinical isolates Acinetobacter baumannii SMAL and MG1 were elucidated. Hot phenol/water extractions of the dry biomasses, followed by enzymatic digestions and repeated ultracentrifugations led to the isolation of polysaccharides that were negative in Western blot analysis utilizing an anti-lipid A antibody, thus proving that they were not the LPS O-antigens but CPSs. Their structures were established on the basis of NMR spectroscopy and GC-MS analyses. The A. baumannii MG1 CPS consisted of a linear aminopolysaccharide with acyl substitution heterogeneity at the N-4 amino group of QuipN4N: 4)-α-d-GlcpNAc-(1→4)-α-l-GalpNAcA-(1→3)-β-d-QuipNAc4NR-(1→ R=3-hydroxybutyrryl or acetyl. The repeating unit of the CPS produced by strain SMAL is a pentasaccharide, already reported for the O-antigen moiety from A. baumannii strain ATCC 17961:, (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The structure of the carbohydrate backbone of the core-lipid A region of the lipooligosaccharide (LOS) of the alkaliphilic and slightly halophilic bacterium Halomonas sp. has been elucidated. The LOS was fully deacylated, dephosphorylated, and reduced at the free reducing end. The structure, obtained by means of compositional analysis, 2D NMR spectroscopy, and MALDI mass spectrometry, was determined as the following: [ structure: see text ]. All sugars are d-pyranoses; Hep is l-glycero-d-manno-heptose and Kdo is 3-deoxy-d-manno-oct-2-ulosonic acid.

The Gram-negative bacterium under study belongs to the genus Kaistella. It was isolated from a soil sample of the Haian Island in China, and it produces a lipophilic polysaccharide characterised by a branched hexasaccharide repeating unit, counting four 6-deoxy-alpha-l-mannose (Rha) residues, one 2-acetamido-2-deoxy-beta-d-glucose (GlcNAc) and a 2-acetamido-2,6-dideoxy-beta-d-galactose (FucNAc) unit. The structure of the repeating unit, assigned through 2D-NMR spectroscopy, is herein reported for the first time: [carbohydrate structure: see text]

Rhizobium rubi, strain DSM 30149, is a Gram negative phytopathogenic bacterium which produces a linear polysaccharide with the following repeating unit: This new structure was determined by spectroscopical and chemical methods. It presents similar lipophilic features reported for another strain of R. rubi. These contrast with features already known for capsular polysaccharide species from symbiontic members of the Rhizobiaceae family, namely highly anionic polymers.