Structural Investigation and Biological Activity of the Lipooligosaccharide from the Psychrophilic Bacterium Pseudoalteromonas haloplanktis TAB 23

Abstract

Pseudoalteromonas haloplanktis TAB 23 is a Gram-negative psychrophilic bacterium isolated from the Antarctic coastal sea. To survive in these conditions psychrophilic bacteria have evolved typical membrane lipids and "antifreeze" proteins to protect the inner side of the microorganism. As for Gram-negative bacteria, the outer membrane is mainly constituted by lipopoly- or lipooligosaccharides (LPS or LOS, respectively), which lean towards the external environment. Despite this, very little is known about the peculiarity of LPS from Gram-negative psychrophilic bacteria and what their role is in adaptation to cold temperature. Here we report the complete structure of the LOS from P. haloplanktis TAB 23. The lipid A was characterized by MALDI-TOF MS analysis and was tested in vitro showing a significant inhibitory effect on the LPS-induced pro-inflammatory cytokine production when added in culture with LPS from Escherichia coli. The product obtained after de-O-acylation of the LPS was analyzed by MALDI-TOF MS revealing the presence of several molecular species, differing in phosphorylation degree and oligosaccharide length. The oligosaccharide portion released after strong alkaline hydrolysis was purified by anion-exchange chromatography-pulsed amperometric detection (HPAEC-PAD) to give three main fractions, characterized by means of 2D NMR spectroscopy, which showed a very short highly phosphorylated saccharidic chain with the following general structure. α-Hepp3R,6R,4R'-(1→5)-α-Kdop4P-(2→6)-β-GlcpN4R-(1→6)-α-GlcpN1P (R=-H(2)PO(3) or -H; R'=α-Galp-(1→4)-β-Galp-(1→ or H-).

A Unique Capsular Polysaccharide Structure from the Psychrophilic Marine Bacterium Colwellia psychrerythraea 34H That Mimics Antifreeze (Glyco)proteins

“…[1][2][3] Because microorganisms are at thermal equilibrium with their environment, it is reasonable to assume that structural and functional components in psychrophiles (optimal growth at ≤ 15°C) have adapted, to some degree, to the requirements of a low temperature existence, 4 including the possible presence of ice crystals in their immediate surroundings. The reported mechanisms of bacterial adaptation to low temperature include the over-expression of cold-shock and heat-shock proteins, the presence of unsaturated and branched fatty acids that maintain membrane fluidity, 5 the different phosphorylation of membrane proteins and lipopolysaccharides, [6][7][8][9][10][11] and the production of cold-active enzymes, 12 antifreeze proteins and cryoprotectants. 13 The latter are chemical substances that generally include small molecules, such as glycine betaine, some amino acids, sugars (glucose, fructose) and sugar alcohols (mannitol, glycerol).…”

Lipid A structural modifications in extreme conditions and identification of unique modifying enzymes to define the Toll-like receptor 4 structure-activity relationship

“…[125,126] In both strains, mass spectra of lipid A extracts produced base peaks due to a bis -phosphorylated, penta-acylated structure containing saturated, C12:0 acyl chains, including three β-hydroxyl substituted chains. However, the location of the only secondary acyl chain differed by occurring as part of an acyloxyamide in the TAB 23[126] strain and as an acyloxyacyl in the TAC 125[125] strain. One interesting observation in P. haloplanktis is that its overall acyl chain incorporation, when taking into account all structures available, tends to be highly heterogeneous.…”

Structural characterization of the lipid A from the LPS of the haloalkaliphilic bacterium Halomonas pantelleriensis

“…A sample of the lipid A fraction (0.5 mg) was dried and methanolyzed, as already described elsewhere (Carillo et al 2011). Briefly, 1 mL of 1-M HCl/CH 3 OH was added to the sample, and the reaction was carried out at 80 °C for 20 h. The crude mixture was extracted twice with hexane.…”

“…This is probably due to the harsh life conditions fundamental for their survival and completely incompatible with the environmental parameters in human body. In this scenario, extremophiles can be a promising source of non-toxic LPSs and lipid A (Carillo et al 2011(Carillo et al , 2013, the chemical structure and biological activity of which are almost completely unknown.…”