Structural characterization of the core region from the lipopolysaccharide of the haloalkaliphilic bacterium Halomonas alkaliantarctica strain CRSS

Abstract

Halophilic and halotolerant Gram-negative bacteria are microorganisms which thrive in high salt environments. LPS are the major components of their outer leaflet, nevertheless very little is known about the role of this molecules in the adaptation mechanisms of extremophiles. Recently we determined the O-chain repeating unit structure of the LPS from Halomonas alkaliantarctica strain CRSS, an haloalkaliphilic Gram-negative bacterium isolated from salt sediments of a saline lake in Cape Russell in Antarctic continent. The polysaccharide is constituted of the trisaccharidic repeating unit: →3)-β-l-Rhap-(1→4)-α-l-Rhap-(1→3)-α-l-Rhap-(1→. In this paper we report the complete core LPS structure from this bacterium. The LPS was hydrolyzed both under mild acid and strong alkaline conditions. The MALDI spectra showed the presence of two glycoforms. The most abundant was recovered after HPAEC purification of the alkaline hydrolyzed product and was characterized by means of 2D-NMR spectroscopy. A comparison of the MALDI-PSD spectra of the two glycoforms suggested that the branched heptose was not stoichiometrically substituted.

Gram‐Negative Extremophile Lipopolysaccharides: Promising Source of Inspiration for a New Generation of Endotoxin Antagonists

“…Core OS and O‐chain moieties – but not lipid A – from H. alkaliantarctica strain CRSS, isolated from the saline lake Cape Russell in Antarctica, have been structurally resolved. The repeating unit of the O‐chain is composed of a trisaccharide of l ‐rhamnose, and the heptasaccharide core region possesses only one Kdo unit, phosphorylated at position O‐4 as depicted below.…”