Structural Elucidation of a Unique Glycerophospho Lipid A From Phenol-Phase Soluble Lipopolysaccharide of Vibrio anguillarum Serovar SJ-41.

In this study, the chemical structure of a unique lipid A derived from the phenol-phase soluble lipopolysaccharide (LPS) of Vibrio anguillarum serovar SJ-41, a virulent marine and freshwater pathogen, was investigated using electrospray ionization with field asymmetric wave ion mobility-Orbitrap mass spectrometry (ESI-FAIMS-MS). The analysis indicated that the obtained lipid A consisted of a heterogeneous mixture of molecules. High-energy collision dissociation tandem mass spectrometry (HCD-MS/MS) allowed the identification of unique chemical motifs of V. anguillarum lipid A. ESI-FAIMS-MS, HCD-MS/MS, and Kendrick mass defect (KMD) plots were used to elucidate V. anguillarum lipid A molecular structure and mixture heterogeneity. Structural analysis revealed significant deviations from canonical lipid A, including the presence of a phospho-glycerol moiety located on primary acyl chain at the O-3 position of reducing sugar end and presence of novel di-hydroxylated primary acyl chains on the N-2' position of the non-reducing sugar end. As far as we know, this is the first report of lipid A structures containing both phospho-glycerol moiety and di-hydroxylated primary acyl chains. KMD plots were employed to investigate structural diversity of lipid A complex mixture. Tandem mass spectrometric analyses and KMD plots allowed the determination of lipid A structural diversity. These findings provide new insights into the lipid A composition of V. anguillarum strain SJ-41 and underscore the need for further studies to explore its biological implications, potentially reshaping our understanding of lipid A and its role in host-pathogen interactions.