Structure of the sialic acid-containing O-specific polysaccharide from Salmonella enterica serovar Toucra O48 lipopolysaccharide

Biochemical and structural basis of sialic acid utilization by gut microbes

The human gastrointestinal (GI) tract harbors diverse microbial communities collectively known as the gut microbiota that exert a profound impact on human health and disease. The repartition and availability of sialic acid derivatives in the gut have a significant impact on the modulation of gut microbes and host susceptibility to infection and inflammation. Although N-acetylneuraminic acid (Neu5Ac) is the main form of sialic acids in humans, the sialic acid family regroups more than 50 structurally and chemically distinct modified derivatives. In the GI tract, sialic acids are found in the terminal location of mucin glycan chains constituting the mucus layer and also come from human milk oligosaccharides in the infant gut or from meat-based foods in adults. The repartition of sialic acid in the GI tract influences the gut microbiota composition and pathogen colonization. In this review, we provide an update on the mechanisms underpinning sialic acid utilization by gut microbes, focusing on sialidases, transporters, and metabolic enzymes.

The Prolonged Treatment of Salmonella enterica Strains with Human Serum Effects in Phenotype Related to Virulence

Salmonella enterica as common pathogens of humans and animals are good model organisms to conduct research on bacterial biology. Because these bacteria can multiply in both the external environments and in the living hosts, they prove their wide adaptability. It has been previously demonstrated that prolonged exposition of Salmonella serotype O48 cells to normal human serum led to an increase in resistance to sera in connection with the synthesis of very long O-antigen. In this work, we have studied the phenotype connected to virulence of Salmonella enterica strains that were subjected to consecutive passages in 50% human serum from platelet-poor plasma (SPPP). We found that eight passages in SPPP may not be enough for the bacteria to become serum-resistant (S. Typhimurium ATCC 14028, S. Senftenberg). Moreover, C1q and C3c complement components bound to Salmonellae (S. Typhimurium ATCC 14028, S. Hammonia) membrane proteins, which composition has been changed after passaging in sera. Interestingly, passages in SPPP generated genetic changes within gene fljB, which translated to cells’ motility (S. Typhimurium ATCC 14028, S. Erlangen). One strain, S. Hammonia exposed to a serum developed a multi-drug resistance (MDR) phenotype and two S. Isaszeg and S. Erlangen tolerance to disinfectants containing quaternary ammonium salts (QAS). Furthermore, colonial morphotypes of the serum adaptants were similar to those produced by starter cultures. These observations suggest that overcoming stressful conditions is manifested on many levels. Despite great phenotypic diversity occurring after prolonged exposition to SPPP, morphotypes of colonies remained unchanged in basic media. This work is an example in which stable morphotypes distinguished by altered virulence can be confusing during laboratory work with life-threatening strains.

Biological functions of sialic acid as a component of bacterial endotoxin

Lipopolysaccharide (endotoxin, LPS) is an important Gram-negative bacteria antigen. LPS of some bacteria contains sialic acid (Neu5Ac) as a component of O-antigen (O-Ag), in this review we present an overview of bacteria in which the presence of Neu5Ac has been confirmed in their outer envelope and the possible ways that bacteria can acquire Neu5Ac. We explain the role of Neu5Ac in bacterial pathogenesis, and also involvement of Neu5Ac in bacterial evading the host innate immunity response and molecular mimicry phenomenon. We also highlight the role of sialic acid in the mechanism of bacterial resistance to action of serum complement. Despite a number of studies on involvement of Neu5Ac in bacterial pathogenesis many aspects of this phenomenon are still not understood.

Lipopolysaccharide lipid A: A promising molecule for new immunity-based therapies and antibiotics

Lipopolysaccharides (LPS) are the main components of the external leaflet of the Gram-negative outer membrane and consist of three different moieties: lipid A, core oligosaccharide, and O-polysaccharide. The lipid A is a glucosamine disaccharide with different levels of acylation and phosphorylation, beside carrying, in certain cases, additional substituents on the sugar backbone. It is also the main immunostimulatory part of the LPS, as its recognition by the host immune system represents a fundamental event for detection of perilous microorganisms. Moreover, an uncontrolled immune response caused by a large amount of circulating LPS can lead to dramatic outcomes for human health, such as septic shock. The immunostimulant properties of an LPS incredibly vary depending on lipid A chemical structure, and for this reason, natural and synthetic variants of the lipid A are under study to develop new drugs that mimic or antagonise its natural effects. Here, we review past and recent findings on the lipid A as an antibiotic target and immune-therapeutic molecule, with a special attention on the crucial role of the chemical structure and its exploitation for conceiving novel strategies for treatment of several immune-related pathologies.

Comparison of the phylogenetic analysis of PFGE profiles and the characteristic of virulence genes in clinical and reptile associated Salmonella strains

BACKGROUND

Salmonella is generally considered as a human pathogen causing typhoid fever and gastrointestinal infections called salmonellosis, with S. Enteritidis and S. Typhimurium strains as the main causative agents. Salmonella enterica strains have a wide host array including humans, birds, pigs, horses, dogs, cats, reptiles, amphibians and insects. Up to 90% of reptiles are the carriers of one or more serovars of Salmonella. Extraintestinal bacterial infections associated with reptiles pose serious health threat to humans. The import of exotic species of reptiles as pet animals to Europe correlates with the emergence of Salmonella serotypes, which not found previously in European countries. The presented study is a new report about Salmonella serotypes associated with exotic reptiles in Poland. The goal of this research was to examine the zoonotic potential of Salmonella strains isolated from reptiles by comparative analysis with S. Enteritidis strains occurring in human population and causing salmonellosis.

RESULTS

The main findings of our work show that exotic reptiles are asymptomatic carriers of Salmonella serovars other than correlated with salmonellosis in humans (S. Enteritidis, S. Typhimurium). Among the isolated Salmonella strains we identified serovars that have not been reported earlier in Poland, for example belonging to subspecies diarizonae and salamae. Restriction analysis with Pulsed-field Gel Electrophoresis (PFGE), showed a great diversity among Salmonella strains isolated from reptiles. Almost all tested strains had distinct restriction patterns. While S. Enteritidis strains were quite homogeneous in term of phylogenetic relations. Most of the tested VGs were common for the two tested groups of Salmonella strains.

CONCLUSIONS

The obtained results show that Salmonella strains isolated from reptiles share most of virulence genes with the S. Enteritidis strains and exhibit a greater phylogenetic diversity than the tested S. Enteritidis population.

Genetics behind the Biosynthesis of Nonulosonic Acid-Containing Lipooligosaccharides in Campylobacter coli

Campylobacter jejuni and Campylobacter coli are the most common causes of bacterial gastroenteritis in the world. Ganglioside mimicry by C. jejuni lipooligosaccharide (LOS) is the triggering factor of Guillain-Barré syndrome (GBS), an acute polyneuropathy. Sialyltransferases from glycosyltransferase family 42 (GT-42) are essential for the expression of ganglioside mimics in C. jejuni Recently, two novel GT-42 genes, cstIV and cstV, have been identified in C. coli Despite being present in ∼11% of currently available C. coli genomes, the biological role of cstIV and cstV is unknown. In the present investigation, mutation studies with two strains expressing either cstIV or cstV were performed and mass spectrometry was used to investigate differences in the chemical composition of LOS. Attempts were made to identify donor and acceptor molecules using in vitro activity tests with recombinant GT-42 enzymes. Here we show that CstIV and CstV are involved in C. coli LOS biosynthesis. In particular, cstV is associated with LOS sialylation, while cstIV is linked to the addition of a diacetylated nonulosonic acid residue.IMPORTANCE Despite the fact that Campylobacter coli a major foodborne pathogen, its glycobiology has been largely neglected. The genetic makeup of the C. coli lipooligosaccharide biosynthesis locus was largely unknown until recently. C. coli harbors a large set of genes associated with lipooligosaccharide biosynthesis, including genes for several putative glycosyltransferases involved in the synthesis of sialylated lipooligosaccharide in Campylobacter jejuni In the present study, C. coli was found to express lipooligosaccharide structures containing sialic acid and other nonulosonate acids. These findings have a strong impact on our understanding of C. coli ecology, host-pathogen interaction, and pathogenesis.

Salmonella O48 Serum Resistance is Connected with the Elongation of the Lipopolysaccharide O-Antigen Containing Sialic Acid

Complement is one of the most important parts of the innate immune system. Some bacteria can gain resistance against the bactericidal action of complement by decorating their outer cell surface with lipopolysaccharides (LPSs) containing a very long O-antigen or with specific outer membrane proteins. Additionally, the presence of sialic acid in the LPS molecules can provide a level of protection for bacteria, likening them to human cells, a phenomenon known as molecular mimicry. Salmonella O48, which contains sialic acid in the O-antigen, is the major cause of reptile-associated salmonellosis, a worldwide public health problem. In this study, we tested the effect of prolonged exposure to human serum on strains from Salmonella serogroup O48, specifically on the O-antigen length. After multiple passages in serum, three out of four tested strains became resistant to serum action. The gas-liquid chromatography/tandem mass spectrometry analysis showed that, for most of the strains, the average length of the LPS O-antigen increased. Thus, we have discovered a link between the resistance of bacterial cells to serum and the elongation of the LPS O-antigen.

Presumable role of outer membrane proteins of Salmonella containing sialylated lipopolysaccharides serovar Ngozi, sv. Isaszeg and subspecies arizonae in determining susceptibility to human serum

Background

The O48 group comprises Salmonella bacteria containing sialic acid in the lipopolysaccharide (LPS). Bacteria with sialylated surface structures are described as pathogens that avoid immunological response of the host by making similar their surface antigens to the host’s tissues (molecular mimicry). It is known that the smooth-type LPS of Salmonella enterica and outer membrane proteins (OMP) PgtE, PagC and Rck mediate serum resistant phenotype by affecting complement system (C). The aim of this study was to investigate C3 component activation by Salmonella O48 LPS and OMP.

Findings

In the present study, we examined C3 component deposition on the three Salmonella O48 strains: S. enterica subspecies enterica serovar Ngozi, S. enterica subsp. enterica sv. Isaszeg, and S.enterica subsp. arizonae containing sialic acid in the O-specific part of LPS. The greatest C3 deposition occurred on Salmonella sv. Isaszeg cells (p < 0.005) as well as on their LPS (low content of sialic acid in LPS) (p < 0.05) after 45 min of incubation in 50% human serum. Weaker C3 deposition ratio on the Salmonella sv. Ngozi (high content of sialic acid in LPS) and Salmonella subsp. arizonae (high content of sialic acid in LPS) cells correlated with the lower C3 activation on their LPS. Immunoblotting revealed that OMP isolated from the tested strains also bound C3 protein fragments.

Conclusions

We suggest that activation of C3 serum protein is dependent on the sialic acid contents in the LPS as well as on the presence of OMP in the range of molecular masses of 35–48 kDa.

Structure and genetic basis of Yersinia similis serotype O:9 O-specific polysaccharide

The O-polysaccharide (OPS, O-Ag) cap of LPS is a major virulence factor of Yersinia species and also serves as a receptor for the binding of lytic bacteriophage φR1-37. Currently, the OPS-based serotyping scheme for the Yersinia pseudotuberculosis complex includes 21 known O-serotypes that follow three distinct lineages: Y. pseudotuberculosis sensu stricto, Y. similis and the Korean group of strains. Elucidation of the Y. pseudotuberculosis complex OPS structures and characterization of the OPS genetics (altogether 18 O-serotypes studied thus far) allows a better understanding of the relationships among the various O serotypes and will facilitate the analysis of the evolutionary processes giving rise to new serotypes. Here we present the characterization of the OPS structure and gene cluster of Y. similis O:9. Bacteriophage φR1-37, which uses the Y. similis O:9 OPS as a receptor, also infects a number of Y. enterocolitica serotypes, including O:3, O:5,27, O:9 and O:50. The Y. similis O:9 OPS structure resembled none of the receptor structures of the Y. enterocolitica strains, suggesting that φR1-37 can recognize several surface receptors, thus promoting broad host specificity.

Structural diversity in Salmonella O antigens and its genetic basis

This review covers the structures and genetics of the 46 O antigens of Salmonella, a major pathogen of humans and domestic animals. The variation in structures underpins the serological specificity of the 46 recognized serogroups. The O antigen is important for the full function and virulence of many bacteria, and the considerable diversity of O antigens can confer selective advantage. Salmonella O antigens can be divided into two major groups: those which have N-acetylglucosamine (GlcNAc) or N-acetylgalactosamine (GalNAc) and those which have galactose (Gal) as the first sugar in the O unit. In recent years, we have determined 21 chemical structures and sequenced 28 gene clusters for GlcNAc-/GalNAc-initiated O antigens, thus completing the structure and DNA sequence data for the 46 Salmonella O antigens. The structures and gene clusters of the GlcNAc-/GalNAc-initiated O antigens were found to be highly diverse, and 24 of them were found to be identical or closely related to Escherichia coli O antigens. Sequence comparisons indicate that all or most of the shared gene clusters were probably present in the common ancestor, although alternative explanations are also possible. In contrast, the better-known eight Gal-initiated O antigens are closely related both in structures and gene cluster sequences.

The chemical composition of endotoxin isolated from intestinal strain of Desulfovibrio desulfuricans

Desulfovibrio desulfuricans anaerobes are constituents of human alimentary tract microflora. There are suggestions that they take part in the pathogenesis of periodontitis and some gastrointestinal inflammatory disorders, such as ulcerative colitis or Crohn's disease. Endotoxin is one of Gram-negative bacteria cellular components that influence these microorganisms pathogenicity. Endotoxin is a lipid-polisaccharide heteropolymer consisting of three elements: lipid A, core oligosaccharide, and O-specific polysaccharide, also called antigen-O. The biological activity of lipopolysaccharide (LPS) is determined by its structure. In this study, we show that rhamnose, fucose, mannose, glucose, galactose, heptose, and 2-keto-3-deoxyoctulosonic acid (Kdo) are constituents of D. desulfuricans endotoxin oligosaccharide core and O-antigen. Lipid A of these bacteria LPS is composed of glucosamine disaccharide substituted by 3-acyloxyacyl residues: ester-bound 3-(dodecanoyloxy)tetradecanoic, 3-(hexadecanoyloxy)tetradecanoic acid, and amide-bound 3-(tetradecanoyloxy)tetradecanoic acid.

Reptiles as a source of Salmonella O48--clinically important bacteria for children: the relationship between resistance to normal cord serum and outer membrane protein patterns

Bacteria of the Salmonella O48 somatic antigen group are clinically important strains causing intestinal dysfunction and diarrhoea, especially in children. The susceptibility of Salmonella O48 strains containing sialic acid (N-acetylneuraminic acid (NeuAc)) in lipopolysaccharide (LPS) to the bactericidal action of normal cord serum (NCS) was determined. The authors' previous results published in Microbial Ecology in 2010 indicated that neither the presence of NeuAc in LPS nor the length of the O-specific part of LPS containing NeuAc plays a decisive role in determining bacterial resistance to the bactericidal activity of normal human serum (NHS), and that the presence of NeuAc in the LPS structure is not sufficient to block the activation of the alternative pathway of complement in NHS. The current results showed that the tested strains showed various sensitivities also to the bactericidal action of NCS. The authors postulate that the presence of certain outer membrane proteins (OMPs) are characteristic of the resistant and sensitive phenotypes of Salmonella O48 strains. To establish a possible relationship between resistance to NCS and OMPs band patterns, ten Salmonella O48 strains were studied as follows: susceptibility to the bactericidal effect of NCS, the mechanisms of NCS activation and OMP band patterns obtained by sodium dodecyl sulphate-polyacrylamide gel electrophoresis.

Structural analysis of lipopolysaccharides from Gram-negative bacteria

This review covers data on composition and structure of lipid A, core, and O-polysaccharide of the known lipopolysaccharides from Gram-negative bacteria. The relationship between the structure and biological activity of lipid A is discussed. The data on roles of core and O-polysaccharide in biological activities of lipopolysaccharides are presented. The structural homology of some oligosaccharide sequences of lipopolysaccharides to gangliosides of human cell membranes is considered.

Sialic acid-containing lipopolysaccharides of Salmonella O48 strains--potential role in camouflage and susceptibility to the bactericidal effect of normal human serum

Sialic acid (N-acetylneuraminic acid, NeuAc) plays an essential role in protecting gram-negative bacteria against the bactericidal activity of serum and may contribute to the pathogenicity of bacteria by mimicking epitopes that resemble host tissue components (molecular mimicry). The role of sialic acid (NeuAc)-containing lipopolysaccharides (LPS) of Salmonella O48 strains in the complement activation of normal human serum (NHS) was investigated. NeuAc-containing lipooligosaccharides cause a downregulation of complement activation and may serve to camouflage the bacterial surface from the immunological response of the host. Serotype O48 Salmonella strains have the O-antigen structure containing NeuAc while its serovars differ in outer membrane protein composition. In this study, the mechanisms of complement activation responsible for killing Salmonella O48 serum-sensitive rods by NHS were established. Four of such mechanisms involving pathways, which are important in the bactericidal mechanism of complement activation, were distinguished: only the classical/lectin pathways, independent activation of the classical/lectin or alternative pathway, parallel activation of the classical/lectin and alternative pathways, and only the alternative pathway important in the bactericidal action of human serum. To further study the role of NeuAc, its content in bacterial cells was determined by gas-liquid chromatography-mass spectrometry in relation to 3-deoxy-D-manno-2-octulosonic acid (Kdo), an inherent constituent of LPS. The results indicate that neither the presence of sialic acid in LPS nor the length of the O-specific part of LPS containing NeuAc plays a decisive role in determining bacterial resistance to the bactericidal activity of complement and that the presence of sialic acid in the structure of LPS is not sufficient to block the activation of the alternative pathway of complement. We observed that for three strains with a very high NeuAc/Kdo ratio the alternative pathways were decisive in the bactericidal action of human serum. The results indicated that those strains are not capable of inhibiting the alternative pathway very effectively. As the pathogenicity of most Salmonella serotypes remains undefined, research into the interactions between these bacterial cells and host organisms is indispensable.

Killing of Gram-negative bacteria with normal human serum and normal bovine serum: use of lysozyme and complement proteins in the death of Salmonella strains O48

Serum is an environment in which bacterial cells should not exist. The serum complement system provides innate defense against microbial infections. It consists of at least 35 proteins, mostly in pre-activated enzymatic forms. The activation of complement is achieved through three major pathways: the classical, alternative, and lectin. Lysozyme, widely present in body fluids, catalyzes the hydrolysis of beta 1,4 linkage between N-acetyloglucosamine and N-acetylmuramic acid in the bacterial cell wall and cooperates with the complement system in the bactericidal action of serum. In this study, ten strains of serotype O48 Salmonella, mainly associated with warm-blooded vertebrates and clinically important causing diarrhea in infants and children, were tested. The results demonstrated that the most efficient killing of Salmonella O48 occurred when all the components of normal bovine serum (NBS) and normal human serum (NHS) cooperated. To prove the role of lysozyme in the bactericidal activity of bovine and human serum, the method of serum adsorption onto bentonite (montmorillonite, MMT) was used. In order to investigate structural transitions accompanying the adsorption of serum components, we applied X-ray diffraction methods. The results of this investigation suggested that apart from lysozyme, other proteins (as, e.g., C3 protein or IgG immunoglobulin) were adsorbed on MMT particles. It was also shown that Ca(2+) cations can be adsorbed on bentonite. This may explain the different sensitivities of the serovars belonging to the same O48 Salmonella serotype to NBS and NHS devoid of lysozyme.

Genetic and biochemical modulation of sialic acid O-acetylation on group B Streptococcus: phenotypic and functional impact

Group B Streptococcus (GBS) is an important human pathogen and a model system for studying the roles of bacterial glycosylation in host-microbe interactions. Sialic acid (Sia), expressed prominently in the GBS capsular polysaccharide (CPS), mimics mammalian cell surface Sia and can interact with host Sia-binding proteins to subvert immune clearance mechanisms. Our earlier work has shown that GBS partially O-acetylates CPS Sia residues and employs an intracellular O-acetylation/de-O-acetylation cycle to control the final level of this surface Sia modification. Here, we examine the effects of point mutations in the NeuD O-acetyltransferase and NeuA O-acetylesterase on specific glycosylation phenotypes of GBS, pinpointing an isogenic strain pair that differs dramatically in the degree of the O-acetyl modification (80% versus 5%) while still expressing comparable levels of overall sialylation. Using these strains, higher levels of O-acetylation were found to protect GBS CPS Sia against enzymatic removal by microbial sialidases and to impede engagement of human Siglec-9, but not to significantly alter the ability of GBS to restrict complement C3b deposition on its surface. Additional experiments demonstrated that pH-induced migration of the O-acetyl modification from the 7- to 9-carbon position had a substantial impact on GBS-Siglec-9 interactions, with 7-O-acetylation exhibiting the strongest interference. These studies show that both the degree and position of the GBS O-acetyl modification influence Sia-specific interactions relevant to the host-pathogen relationship. We conclude that native GBS likely expresses a phenotype of intermediate Sia O-acetylation to strike a balance between competing selective pressures present in the host environment.

The mechanisms of activation of normal human serum complement byEscherichia coli strains with K1 surface antigen

Ten E. coli K1 strains isolated from the urine of children with urinary tract infections were sensitive to the bactericidal action of normal human serum (NHS). The role of the particular mechanisms of complement activation was determined in the process of killing these strains, showing variable sensitivity to the bactericidal action of NHS; three mechanisms of activation of human complement were observed. Important role of alternative pathway activation in the bactericidal action of NHS against E. coli K1 strains independent of the classical and lectin pathways was not established.

Structures of the biological repeating units in the O-chain polysaccharides ofHafnia alveistrains having a typical lipopolysaccharide outer core region

Earlier, the structures of the O-chain polysaccharides of the lipopolysaccharides (LPS) of a number of Hafnia alvei strains have been established. However, it remained unknown, which is the first and the last monosaccharide of the O-chain. This is defined by the structure of the so-called biological repeating unit (O-unit), which is pre-assembled and then polymerised in the course of biosynthesis of bacterial polysaccharides by the Wzy-dependent pathway. Now we report on the structures of the O-units in 10 H. alvei strains. The LPS were cleaved by mild acid hydrolysis and oligosaccharide fractions IIIa and IIIb were isolated by gel chromatography subsequently on Sephadex G-50 and BioGel P-2 and studied by methylation analysis and NMR spectroscopy. Fraction IIIb was found to represent the core oligosaccharide containing a terminal upstream alpha-d-Glc-(1-->3)-alpha-d-Glc or alpha-d-Gal-(1-->3)-alpha-d-Glc disaccharide in the outer region that is typical of H. alvei. Fraction IIIa consists of the LPS core with one O-unit linked by a 3-substituted beta-d-GalNAc residue (in strains PCM 1189 and PCM 1546) or a 3-substituted beta-d-GlcNAc residue (in the other strains studied). In most strains examined the beta-configuration of the d-GlcNAc linkage in the first O-unit attached to the core is the same and in some strains is opposite to that found in the interior O-units of the O-chain polysaccharide. Various monosaccharides, including d-Glc, d-Gal, d-GlcA and acyl derivatives of 3-amino-3,6-dideoxy-d-glucose or 4-amino-4,6-dideoxy-d-glucose, occupy the non-reducing end of the O-unit.

Structural and genetic characterization of enterohemorrhagic Escherichia coli O145 O antigen and development of an O145 serogroup-specific PCR assay

Enterohemorrhagic Escherichia coli O145 strains are emerging as causes of hemorrhagic colitis and hemolytic uremic syndrome. In this study, we present the structure of the E. coli O145 O antigen and the sequence of its gene cluster. The O145 antigen has repeat units containing three monosaccharide residues: 2-acetamido-2-deoxy-D-glucose (GlcNAc), 2-acetamidoylamino-2,6-dideoxy-L-galactose, and N-acetylneuraminic acid. It is very closely related to Salmonella enterica serovar Touera and S. enterica subsp. arizonae O21 antigen. The E. coli O145 gene cluster is located between the JUMPStart sequence and the gnd gene and consists of 15 open reading frames. Putative genes for the synthesis of the O-antigen constituents, for sugar transferase, and for O-antigen processing were annotated based on sequence similarities and the presence of conserved regions. The putative genes located in the E. coli O145 O-antigen gene cluster accounted for all functions expected for synthesis of the structure. An E. coli O145 serogroup-specific PCR assay based on the genes wzx and wzy was also developed by screening E. coli and Shigella isolates of different serotypes.

Analysis and glycosyl composition of the exopolysaccharide isolated from the floc-forming wastewater bacterium Thauera sp. MZ1T

Conditions were developed for the reproducible production, isolation and characterization of a novel microbial extracellular polysaccharide believed to be involved in transient viscous bulking at an industrial wastewater treatment plant. The exopolysaccharide was extracted from cell-free culture supernatants of Thauera sp. strain MZ1T grown on a minimal medium with succinate. The purified polymer was found to be approximately 260 kDa in size by gel-permeation chromatography. The GC-MS analysis of the alditol acetate and per-O-trimethylsilyl methyl glycoside derivatives revealed that the exopolysaccharide was composed of four monosaccharides including: rhamnose, galacturonic acid, N-acetylglucosamine and N-acetylfucosamine. Glucose, which also appeared at low levels, is most likely from a co-eluting glucan. The FTIR and NMR spectroscopic analyses further revealed the presence of esterified component groups on the polymer. These results represent the first published description of a polysaccharide from a member of the genus Thauera, and lay the foundation for a deeper understanding of the factors potentially involved in zoogloeal cluster formation and viscous bulking.

Structural analysis of the Lactobacillus rhamnosus strain KL37C exopolysaccharide

The exopolysaccharide from the lactic acid bacterium Lactobacillus rhamnosus strain KL37C isolated from human intestinal flora was prepared by sonication of bacterial cell mass suspended in water followed by centrifugation and cold ethanol precipitation of the supernatant. The polysaccharide material was purified by gel permeation chromatography on an TSK HW-50 column and characterised using chemical and enzymatic methods. On the basis of sugar and methylation analysis and 1H, 13C, 1D and 2D NMR spectroscopy the exopolysaccharide was shown to be composed of the following pentasaccharide repeating unit:-->3)-alpha-D-Glcp-(1-->2)-beta-D-Galf-(1-->6)-alpha-D-Galp-(1-->6)-alpha-D-Glcp-(1-->3)-beta-D-Galf-(1-->

Bactericidal activity of normal cord serum (NCS) against Gram-negative rods with sialic acid-containing lipopolysaccharides (LPS)

Sialic acids, that are important constituents of animal tissue glycoconjugates, are also present in antigens of some bacterial strains. Capsular polysaccharides with sialic acid have been extensively studied whereas little is known on lipopolysaccharides which contain sialic acid. The susceptibility of Gram-negative strains with sialic acid-containing lipopolysaccharides to the bactericidal action of the sera of newborns was examined. The strains investigated showed variable sensitivity to the bactericidal action of normal cord serum.