Structural Characterization of the Core Oligosaccharide Isolated from the Lipo­polysaccharide of the Psychrophilic Bacterium Colwellia psychrerythraea Strain 34H†

Cold-adapted bacteria are microorganisms that thrive at very low temperatures in permanently cold environments (0–10 °C). Their ability to survive under these harsh conditions is the result of molecular evolution and adaptations, which include the structural modification of the phospholipid membrane. To give insight into the role of the membrane in the mechanisms of adaptation to low temperature, the characterization of other cell-wall components is necessary. Among these components, the lipopolysaccharides are complex amphiphilic macromolecules embedded in the outer leaflet of the external membrane, of which they are the major constituents. The cold-adapted Colwellia psychrerythraea 34H bacterium, living in deep sea and Arctic and Antarctic sea ice, was cultivated at 4 °C. The lipooligosaccharide (LOS) was isolated and analysed by means of chemical analysis. Then it was degraded either by mild hydrazinolysis (O-deacylation) or hot KOH (4 M; N-deacylation). Both products were investigated in detail by 1H and 13C NMR spectroscopy and by ESI FT-ICR mass spectrometry. The oligosaccharide portion consists of a unique and very short species with the following general structure: α-L-Col-(12)-α-D-GalA-(12)-α-D-Man-[3-P-D-Gro]-(15)-α-D-Kdo-4-P-Lipid-A.