Unusual Lipid A from a Cold-Adapted Bacterium: Detailed Structural Characterization.

Colwellia psychrerythraea 34H is a Gram-negative cold-adapted microorganism that adopts many strategies to cope with the limitations associated with the low temperatures of its habitat. In this study, we report the complete characterization of the lipid A moiety from the lipopolysaccharide of Colwellia. Lipid A and its partially deacylated derivative were completely characterized by high-resolution mass spectrometry, NMR spectroscopy, and chemical analysis. An unusual structure with a 3-hydroxy unsaturated tetradecenoic acid as a component of the primary acylation pattern was identified. In addition, the presence of a partially acylated phosphoglycerol moiety on the secondary acylation site at the 3-position of the reducing 2-amino-2-deoxyglucopyranose unit caused tremendous natural heterogeneity in the structure of lipid A. Biological-activity assays indicated that C. psychrerythraea 34H lipid A did not show an agonistic or antagonistic effect upon testing in human macrophages.