Structural studies on the core and the O‐polysaccharide repeating unit of Pseudomonas aeruginosa immunotype 1 lipopolysaccharide

Abstract

The structure of the lipopolysaccharide (LPS) of Pseudomonas aeruginosa immunotype 1 was studied after mild acid and strong alkaline degradations by MS and NMR spectroscopy. Three types of LPS molecules were found, including those with an unsubstituted glycoform 1 core (A) or an isomeric glycoform 2 core substituted with one O‐polysaccharide repeating unit (B) or with a long‐chain O‐polysaccharide. Therefore, of two core glycoforms, only glycoform 2 accepts the O‐polysaccharide. In the structures A and B, Kdo, Hep, Hep7Cm, GalNAcAN3Ac, GalNFoAN, QuiNAc, GalNAla represent 3‐deoxy‐d‐manno‐octulosonic acid, l‐glycero‐d‐manno‐heptose, 7‐O‐carbamoyl‐l‐glycero‐d‐manno‐heptose, 2‐acetamido‐3‐O‐acetyl‐2‐deoxygalacturonamide, 2‐formamido‐2‐deoxygalacturonamide, 2‐acetamido‐2,6‐dideoxyglucose and 2‐(l‐alanylamino)‐2‐deoxygalactose, respectively; all sugars are in the pyranose form and have the d configuration unless otherwise stated. One or more phosphorylation sites may be occupied by diphosphate groups. In a minority of the LPS molecules, an O‐acetyl group is present in the outer core region at unknown position. The site and the configuration of the linkage between the O‐polysaccharide and the core and the structure of the O‐polysaccharide repeating unit were defined in P. aeruginosa immunotype 1. The QuiNAc residue linked to the Rha residue of the core was found to have the β configuration, whereas in the interior repeating units of the O‐polysaccharide this residue is in the α‐configuration. The data obtained are in accordance with the initiation of biosynthesis of the O‐polysaccharide of P. aeruginosa O6, which is closely related to immunotype 1, by transfer of d‐QuiNAc‐1‐P to undecaprenyl phosphate followed by synthesis of the repeating O‐antigen tetrasaccharide.

Alginate is not a significant component of the extracellular polysaccharide matrix of PA14 and PAO1Pseudomonas aeruginosabiofilms

“…Many of the sugars identified in our carbohydrate analysis correspond to sugars found in P. aeruginosa LPS (e.g., KDO, N-acetyl sugars, glucose, etc). Both rhamnose and glucose are core monosaccharides, whereas rhamnose is also an important component of A-band LPS (44,45). The presence of 2-linked and 3-linked rhamnose sugars further supports that our EPS samples contain LPS sugars (Table 4).…”

Pseudomonas aeruginosa lipopolysaccharide: A major virulence factor, initiator of inflammation and target for effective immunity

“…Bound to the second heptose residue, Hep II , is a 7-O-carbamyl group (Beckmann et al, 1995), which is found in the LPS of other types of pseudomonads (Knirel et al, 1996). The 2 heptose residues are often phosphorylated at positions 2 and 4 of Hep I and position 6 of Hep II (Bystrova et al, 2002;Knirel et al, 2001;Sadovskaya et al, 2000). Phosphate substituents can be mono-, di-or even tri-phosphates, with most analyzed P. aeruginosa LPS having some triphosphate, which, to date, has only been detected in the LPS of this bacterial species.…”

“…The outer core of the P. aeruginosa LPS is usually synthesized as 2 different isoforms or glycoforms by an individual strain (Bystrova et al, 2002(Bystrova et al, ,2006Sadovskaya et al, 2000). Both outer-core glycoforms contain an N-alanylated galactosamine residue, 3 D-glucose residues, and one L-rhamnose residue the position of which differs in the 2 glycoforms (Fig.…”

Biophysical and biochemical studies of the outer membrane proteins OprG and OprH from Pseudomonas aeruginosa

“…7-O-carbamyl group is bound to the second heptose residue, HepII [22], and is also found in the LPS of other types of pseudomonads [23]. The two heptose residues are often phosphorylated at positions 2 and 4 of HepI and position 6 of HepII [24][25][26].Phosphate substituents are mainly mono-and di-phosphates, however, tri-phosphates are also commonly found, which is unique to P. aeruginosa. Phosphorylation of the P. aeruginosa LPS inner core is necessary for the bacterial survival; a mutation in the waaP gene that phosphorylates position 4 of the HepI groups is lethal for the organism [27].…”

“…O-antigens are built of repeating units of oligosaccharides, the chemical structures of which are strain-specific. The outer cores of the P. aeruginosa LPS are usually synthesized as two different isoforms or glycoforms by individual strains [20,24,26]. Both isoforms contain an N-alanylated galactosamine residue, three Dglucose residues and one L-rhamnose residue, the specific position of which depends on the isoform (Fig.…”