Structural investigation on the lipooligosaccharide fraction of psychrophilic Pseudoalteromonas haloplanktis TAC 125 bacterium

The core structure of the cell-wall lipooligosaccharide (LOS) fraction of a n Antarctic Gram-negative bacterium, Pseudoalteromonas haloplanktis TAC 125 strain, was determined to be deacetylated alditols. These were obtained fr om native LOS fraction by O-deacylation, dephosphorylation, reduction and f inally N-deacylation. Two novel structures were detected, the more highly r epresented molecule consisting of the following hexasaccharide chain: alpha -D-ManpNH(2)-(1-->3)-beta -D-Galp-(1-->4)-alpha -L-glycero-D-manno-Hepp-(1 -->5)-alpha -D-Kdo(2-->6)-beta -D-GlcpNH(2)-(1-->6)-D-GlcNH(2)(ol) while th e corresponding pentasaccharide, lacking the ManpNH(2) residue, was less ab undant. To the best of our knowledge, the structural investigation presented here, mainly performed by NMR and MS methods, is the first report of the lipopoly saccharide fraction of a psychrophilic bacterium.