The structure of the O-polysaccharide from the lipopolysaccharide of Providencia stuartii O47

Structural characterization of oligosaccharide from Dendrobium officinale and its properties in vitro digestion and fecal fermentation

Oligosaccharides from Dendrobium officinale (DOO) is a kind of new potential prebiotic for health. In this study, structural characteristics, digestion properties and regulatory function on intestinal flora of DOO were investigated. An oligosaccharide, DOO 1-1, was purified by DEAE-Sepharose Fast Flow and Sephadex G-25, and its physicochemical properties were characterized as a glucomannan oligosaccharide with a molecular weight of 1560 Da (DP = 9). In vitro simulated digestion, it proved that the structure of DOO 1-1 was degraded hardly in the simulated gastric and small intestinal fluid. By evaluating the gas, short-chain fatty acids and intestinal microbiota in vitro fermentation, DOO has an excellent regulatory effect on intestinal microbiota, especially promoting the proliferation of Bacteroidetes and Actinobacteria. Therefore, DOO can be used as a potential prebiotic in functional foods.

Total synthesis of the O-antigen repeating unit of Providencia stuartii O49 serotype through linear and one-pot assemblies

Capsular polysaccharides of pathogenic bacteria have been reported to be effective vaccines against diseases caused by them. Providencia stuartii is a class of enterobacteria of the family Providencia that is responsible for several antibiotic resistant infections, particularly urinary tract infections of patients with prolonged catheterization in hospital settings. Towards the goal of development of vaccine candidates against this pathogen, we herein report the total synthesis of a trisaccharide repeating unit of the O-antigen polysaccharide of the P. stuartii O49 serotype containing the →6)-β-ᴅ-Galp-(1→3)-β-ᴅ-GalpNAc(1→4)-α-ᴅ-Galp(1→ linkage. The synthesis of the trisaccharide repeating unit was carried out first by a linear strategy involving the [1 + (1 + 1 = 2)] assembly, followed by a one-pot synthesis involving [1 + 1 + 1] strategy from the corresponding monosaccharides. The one-pot method provided a higher yield of the protected trisaccharide intermediate (73%) compared to the two step synthesis (66%). The protected trisaccharide was then deprotected and N-acetylated to finally afford the desired trisaccharide repeating unit as its α-p-methoxyphenyl glycoside.

O-antigens of bacteria of the genus providencia: structure, serology, genetics, and biosynthesis

The genus Providencia consists of eight species of opportunistic pathogenic enterobacteria that can cause enteric diseases and urinary tract infections. The existing combined serological classification scheme of three species, P. alcalifaciens, P. stuartii, and P. rustigianii, is based on the specificity of O-antigens (O-polysaccharides) and comprises 63 O-serogroups. Differences between serogroups are related to polymorphism at a specific genome locus, the O-antigen gene cluster, responsible for O-antigen biosynthesis. This review presents data on structures of 36 O-antigens of Providencia, many of which contain unusual monosaccharides and non-carbohydrate components. The structural data correlate with the immunospecificity of the O-antigens and enable substantiation on a molecular level of serological relationships within the genus Providencia and between strains of Providencia and bacteria of the genera Proteus, Escherichia, and Salmonella. Peculiar features of the O-antigen gene cluster organization in 10 Providencia serogroups and biosynthetic pathways of nucleotide precursors of specific monosaccharide components of the O-antigens also are discussed.

Preliminary investigation of a highly sulfated galactofucan fraction isolated from the brown alga Sargassum polycystum

A fucoidan preparation was isolated from the brown alga Sargassum polycystum (Fucales, Sargassaceae). The preparation was fractionated by anion-exchange chromatography, and two highly sulfated fractions F3 and F4 were obtained. The fractions were quite similar in composition, but different in chemical structure. F4 was analyzed by chemical methods, including desulfation, methylation, Smith degradation, and partial acid hydrolysis with mass-spectrometric monitoring, as well as by NMR spectroscopy. Several 2D NMR procedures, including HMQC-TOCSY and HMQC-NOESY, were used to obtain reliable structural information from the complex spectra. Molecules of F4 were shown to contain a backbone built up mainly of 3-linked α-L-fucopyranose 4-sulfate residues, as in many other fucoidans, but rather short sequences of these residues are interspersed by single 2-linked α-D-galactopyranose residues also sulfated at position 4. This rather unusual structural feature should have a great influence on the conformation of the polymeric molecule and may be important for biological activity of the polysaccharide. Hence, F4 is an example of a new sulfated galactofucan isolated from the brown alga. According to the data obtained, the distribution of galactose residues along the polysaccharide backbone seems to be not strictly regular, but the definitive sequence of monomers in the polymeric molecules awaits additional investigation.

Localization and molecular characterization of putative O antigen gene clusters of Providencia species

Enterobacteria of the genus Providencia are opportunistic human pathogens associated with urinary tract and wound infections, as well as enteric diseases. The lipopolysaccharide (LPS) O antigen confers major antigenic variability upon the cell surface and is used for serotyping of Gram-negative bacteria. Recently, Providencia O antigen structures have been extensively studied, but no data on the location and organization of the O antigen gene cluster have been reported. In this study, the four Providencia genome sequences available were analysed, and the putative O antigen gene cluster was identified in the polymorphic locus between the cpxA and yibK genes. This finding provided the necessary information for designing primers, and cloning and sequencing the O antigen gene clusters from five more Providencia alcalifaciens strains. The gene functions predicted in silico were in agreement with the known O antigen structures; furthermore, annotation of the genes involved in the three-step synthesis of GDP-colitose (gmd, colD and colC) was supported by cloning and biochemical characterization of the corresponding enzymes. In one strain (P. alcalifaciens O39), no polysaccharide product of the gene cluster in the cpxA-yibK locus was found, and hence genes for synthesis of the existing O antigen are located elsewhere in the genome. In addition to the putative O antigen synthesis genes, homologues of wza, wzb, wzc and (in three strains) wzi, required for the surface expression of capsular polysaccharides, were found upstream of yibK in all species except Providencia rustigianii, suggesting that the LPS of these species may be attributed to the so-called K LPS (K(LPS)). The data obtained open a way for development of a PCR-based typing method for identification of Providencia isolates.

The O-polysaccharide from the lipopolysaccharide of Providencia stuartii O44 contains l-quinovose, a 6-deoxy sugar rarely occurring in bacterial polysaccharides

The O-polysaccharide (O-antigen) of Providencia stuartii O44:H4 (strain 3768/51) was obtained by mild acid degradation of the lipopolysaccharide and studied by sugar and methylation analyses along with (1)H and (13)C NMR spectroscopy, including 2D (1)H,(1)H COSY, TOCSY, ROESY, and H-detected (1)H,(13)C HSQC, and HMQC-TOCSY experiments. The O-polysaccharide was found to have a branched hexasaccharide repeating unit of the following structure: [Formula: see text].

Structure of the O-polysaccharide from the lipopolysaccharide of Providencia stuartii O43 containing an amide of d-galacturonic acid with l-serine

The O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Providencia stuartii O43:H28 and studied by sugar and methylation analyses, Smith degradation and 1H and 13C NMR spectroscopy, including 2D ROESY, and H-detected 1H, 13C HSQC and HMBC experiments, as well as a NOESY experiment in a 9:1 H2O/D2O mixture to reveal correlations for NH protons. It was found that the polysaccharide is built up of linear tetrasaccharide repeating units containing an amide of D-galacturonic acid with L-serine [D-GalA6(L-Ser)] and has the following structure:[3)-beta-D-GalpA6(L-Ser)-(1-->3)-beta-D-GlcpNAc-(1-->2)-alpha-D-Rhap4NAc-(1-->4)-beta-D-GlcpA-(1-->]n.

The structure of the O-polysaccharide from the lipopolysaccharide of Providencia stuartii O57 containing an amide of d-galacturonic acid with l-alanine

The O-polysaccharide (O-antigen) was obtained by mild acid degradation of the lipopolysaccharide of Providencia stuartii O57:H29. Studies by sugar and methylation analyses along with (1)H and (13)C NMR spectroscopy, including two-dimensional (1)H,(1)H COSY, TOCSY, ROESY, H-detected (1)H,(13)C HSQC, and HMBC experiments, showed that the polysaccharide contains an amide of D-galacturonic acid with L-alanine and has the following pentasaccharide repeating unit: [formula: see text]