Structure Elucidation of the Highly Heterogeneous Lipid A from the Lipopolysaccharide of the Gram-Negative Extremophile Bacterium Halomonas Magadiensis Strain 21 M1 Lipopolysaccharide of the Gram-Negative Extremophile Bacterium Halomonas Magadiensis Strai

Halomonas magadiensis (formerly named Halomonas magadii) is a Gram-negative extremophilic and alkaliphilic bacterium isolated from Lake Magadi, which is located in the East African Rift Valley. Several members of the halomonad group of bacteria have been shown to inhabit the alkaline brines, including a new member, Halomonas magadiensis strain 21 M1 (NCIMB 13595), an organism that grows at high pH and relatively high salt concentration. The unusual structure of the lipid A family derived from the lipopolysaccharide of Halomonas magadiensis is reported herein. The structure was determined using chemical analysis, NMR spectroscopy and MALDI-TOF mass spectrometry. Lipid A was also analysed after either de-O-acylation or dephosphorylation. The resultant mixture was very heterogeneous in fatty acid substitution, from heptaacyl to triacyl species. The various lipid A molecules obtained by the removal of one or more acyl substituents from the heptaacyl species are described below.