The Deep-Sea Polyextremophile Halobacteroides lacunaris TB21 Rough-Type LPS: Structure and Inhibitory Activity towards Toxic LPS

Abstract

The structural characterization of the lipopolysaccharide (LPS) from extremophiles has important implications in several biomedical and therapeutic applications. The polyextremophile Gram-negative bacterium Halobacteroides lacunaris TB21, isolated from one of the most extreme habitats on our planet, the deep-sea hypersaline anoxic basin Thetis, represents a fascinating microorganism to investigate in terms of its LPS component. Here we report the elucidation of the full structure of the R-type LPS isolated from H. lacunaris TB21 that was attained through a multi-technique approach comprising chemical analyses, NMR spectroscopy, and Matrix-Assisted Laser Desorption Ionization (MALDI) mass spectrometry. Furthermore, cellular immunology studies were executed on the pure R-LPS revealing a very interesting effect on human innate immunity as an inhibitor of the toxic Escherichia coli LPS.

Lipid A Structure and Immunoinhibitory Effect of the Marine Bacterium Cobetia pacifica KMM 3879T

“…Even more appealing was the observation of the potent inhibitory activity shown by the C. pacifica KMM 3879 T LPS towards the toxic effects of the E. coli LPS on the human TLR4/MD2 complex. This fascinating property has been extensively reported for tetra‐acylated lipid A, such as lipid IV A , and also for some other marine bacteria such as Halomonas megadiensis and Halobacteroides lacunaris , as well as for the thermophilic bacterium Thermomonas hydrothermalis . The TLR4/MD2 inhibitory action of the C. pacifica KMM 3879 T LPS may be explained by the occurrence of hypo‐acylated lipid A species, namely tetra‐ and penta‐acylated, in addition to the hexa‐acylated forms; this could result in a very weak elicitation of an immune response, while still maintaining the ability to robustly compete with the toxic E. coli LPS for binding to the TLR4/MD2 complex.…”

Biopolymer Skeleton Produced by Rhizobium radiobacter: Stoichiometric Alternation of Glycosidic and Amidic Bonds in the Lipopolysaccharide O‐Antigen

“…Indeed, the alkaline treatment left attached Poly2 , the OPS of the LPS, to the fragment containing the core region and the deacylated lipid A moiety. Identification of this last moiety was driven by the characteristic multiplicity and chemical shift of the signal at δ =5.63 ppm, which corresponds to the proton signal of the phosphorylated anomeric position of the reducing glucosamine of lipid A . Given the low intensity of this and other signals, it was not possible to gather further information on these monosaccharide residues or about their sequence.…”

The Lipid A Structure from the Marine Sponge Symbiont Endozoicomonas sp. HEX 311

“…HEX 311 lipid A (Scheme ) is mainly composed of tetra‐ and triacylated species, that is, a highly hypoacylated species, which might be poorly recognized by the sponge immune system. Moreover, if hexaacylated forms occur, these present a 3+3 distribution of the acyl chains, which are also typically correlated to a weak immunopotential . Therefore, the expression of lipid A with structural features leading to weak immunoactivity might be a key requirement to establish the successful symbiosis between the microbe and sponge.…”