Structural characterization of the core oligosaccharide isolated from the lipopolysaccharide of the haloalkaliphilic bacterium Salinivibrio sharmensis strain BAG(T).

Salinivibrio genus is included in the family Vibrionaceae and up to now is constituted by only five members. All the species are moderately halophilic bacteria found in salted meats, brines, and several hypersaline environments. Halophilic microorganisms are good sources of biomolecules, such as proteases, that have a great industrial interest as demonstrated by recent studies. All these bacteria possess on their outer membrane amphiphilic molecules named lipopolysaccharides, which are of great interest because of their involvement in the mechanisms of interaction between the microbial life and environmental factors. A novel haloalkaliphilic, facultative anaerobic and Gram-negative Salinivibrio-like microorganism, named S. sharmensis strain BAG(T), was recovered from a saline lake in Ras Mohammed Park (Egypt). The aim of this work is the isolation and structural characterization of the core oligosaccharidic fraction of the lipopolysaccharide from this bacterium. By means of HPAEC-PAD we were able to purify two glycoforms, fully depicted by ESI FT-ICR mass spectrometry, chemical analysis, and NMR spectroscopy. Like other haloalkaliphilic bacteria, the core region was found to be characterized by the presence of several negatively charged residues, such as uronic acids. All the data contributed to give the following structure α-D-Glc-(1-->4)-β-D-GalNAc-(1--4)-β-D-Glc1-->4α-D-GlcA-(1-->2)-α-L,D-Hep-(1-->3)-α-D,D-Hep-(1-->5)-α-D-Kdo4P-(2-->6)-LipidA2<--1β-D-GlcA.