Yu. A. Knirel

Structural features of sulfated chitosans

Abstract Chitosan sulfates prepared by different methods were analyzed by 13C NMR spectroscopy. It was shown that the sulfation conditions of chitosan essentially affect the position and degree of substitution with sulfate in derivatives of chitosan. Sulfated products obtained under homogeneous conditions are characterized by more heterogeneity and they have to be considered as copolymers of chitosan 6-O-monosulfate and 3,6-O-disulfate, whereas those produced by semi-heterogeneous synthesis may be considered preferentially as chitosan 3,6-O-disulfate.

Antigenic polysaccharides of bacteria

The specific polysaccharide of Sh. boydii 6 is an acid hexosaminoglycan, the repeating unit of which is built from mannose, galactose, galactosamine, and glucuronic acid residues in a 2∶1∶1∶1 ratio.

Human tandem-repeat-type galectins bind bacterial non-βGal polysaccharides

Galectins are multifunctional effectors, for example acting as regulators of cell growth via protein-glycan interactions. The observation of capacity to kill bacteria for two tandem-repeat-type galectins, which target histo-blood epitopes toward this end (Stowell et al. Nat. Med. 16:295–301, 2010), prompted us to establish an array with bacterial polysaccharides. We addressed the question whether sugar determinants other than β-galactosides may be docking sites, using human galectins-4, -8, and -9. Positive controls with histo-blood group ABH-epitopes and the E. coli 086 polysaccharide ascertained the suitability of the set-up. Significant signal generation, depending on type of galectin and polysacchride, was obtained. Presence of cognate β-galactoside-related epitopes within a polysaccharide chain or its branch will not automatically establish binding properties, and structural constellations lacking galactosides, like rhamnan, were found to be active. These data establish the array as valuable screening tool, giving direction to further functional and structural studies.

Biological properties and structure of the lipopolysaccharide of a vaccine strain of Francisella tularensis generated by inactivation of a quorum sensing system gene qseC

A knockout mutant with a deletion in a quorum sensing system gene qseC was generated from the vaccine strain Francisella tularensis 15 by site-directed mutagenesis. The variant with the inactivated gene qseC differed from the parental strain in growth rate on solid nutrient medium but had the same growth dynamics in liquid nutrient medium. The mutation abolished almost completely the resistance of the vaccine strain to normal rabbit serum and its ability to survive in macrophages; in addition, the strain lost the residual virulence. A significant phenotypic alteration was observed in the lipopolysaccharide of F. tularensis. Particularly, the mutant strain synthesized no noticeable amount of the lipopolysaccharide with the high-molecular-mass O-polysaccharide, presumably as a result of impairing biosynthesis of the repeating unit, namely, a loss of the ability to incorporate a formyl group, an N-acyl substituent of 4-amino-4,6-dideoxy-D-glucose.

Structural peculiarities of the O-specific polysaccharides of Azospirillum bacteria of serogroup III

Lipopolysaccharides and O-specific polysaccharides were isolated from the outer membrane of bacterial cells of three strains belonging to two Azospirillum species, and their structures were established by monosaccharide analysis including determination of the absolute configurations, methylation analysis, and one- and two-dimensional NMR spectroscopy. It was shown that while having the identical composition, the O-polysaccharides have different branched tetrasaccharide repeating units. Two neutral polysaccharides were found in the lipopolysaccharide of A. brasilense 54, and the structure for the predominant O-polysaccharide was determined. The structural data, together with results of serological studies, enabled assignment of strains examined to a novel serogroup, III. The chemical basis for the serological relatedness among the azospirilla of this serogroup is presumably the presence of a common →3)-α-L-Rhap-(1→2)-α-L-Rhap-(1→3)-α-L-Rhap-(1→oligosaccharide motif in their O-polysaccharides.

Structural diversity of O-polysaccharides and serological classification of Pseudomonas syringae pv. garcae and other strains of genomospecies 4

Novel O-serotypes were revealed among Pseudomonas syringae pv. garcae strains by using a set of mouse monoclonal antibodies specific to the lipopolysaccharide O-polysaccharide. Structural studies showed that the O-polysaccharide of P. syringae pv. garcae NCPPB 2708 is a hitherto unknown linear L-rhamnan lacking strict regularity and having two oligosaccharide repeating units I and II, which differ in the position of substitution in one of the rhamnose residues and have the following structures: I:→3)-α-L Rha (1→2)-α- L Rha (1→2)-α-L-Rha-(1→3)-α-L Rha (1→;II: →2)-α-L-Rha-(1→3) α-L-Rha-(1→2)-α-L-Rha-(1→3)-α-L Rha (1→.The branched O-polysaccharides of P. syringae pv. garcae ICMP 8047 and NCPPB 588T have the same L-rhamnan backbone with repeating units I and II and a lateral chain of α1→4)- or α1→3)-linked residues of 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc). Several monoclonal antibody epitopes associated with the L-rhamnan backbone or the lateral α-D-Fuc3NAc residues were characterized.

Characterization of the lipopolysaccharide and structure of the O-specific polysaccharide of the bacterium Pseudomonas syringae pv. atrofaciens IMV 948.

AbstractLipopolysaccharide (LPS) was isolated from the phytopathogenic bacterium Pseudomonas syringae pv. atrofaciens IMV 948 by mild extraction of the microbial cells with saline, and the properties, composition, and structure of the LPS were studied. The LPS showed low toxicity in D-galactosamine-sensitized mice and low biological activity in plants. Structural components of LPS–lipid A, core oligosaccharide, and O-specific polysaccharide (OPS)–were obtained by mild acid degradation and characterized. The lipid A contained fatty acids 3-HO-C10:0, C12:0, 2-HO-C12:0, 3-HO-C12:0, C16:0, C16:1, C18:0, and C18:1, as well as components of the hydrophilic moiety: GlcN, ethanolamine, phosphate, and phosphoethanolamine. The LPS core contained components typical of pseudomonads: glucose, rhamnose (Rha), L-glycero-D-manno-heptose, GlcN, GalN, 2-keto-3-deoxy-D-manno-octonic acid, alanine, and phosphate. The OPS consisted of L-Rha and D-GlcNAc in the ratio 4 : 1 and was structurally heterogeneous. The main pentasaccharide repeating unit of the OPS has the following structure:

The structure of the O-specific polysaccharide from a mutant of nitrogen-fixing rhizobacterium Azospirillum brasilense Sp245 with an altered plasmid content

\beta - D - GlcpNAc1\downarrow2\to 2) - \alpha -L -Rhap-(1 \to 2) - \alpha -L -Rhap-(1 \to 3) - \alpha -L -Rhap-(1 \to 3) - \alpha -L -Rhap-(1 \to