Structural studies of the O-specific side-chains of the lipopolysaccharide from Yersinia enterocolitica Ye 128

Yersinia Phages and Food Safety

One of the human- and animal-pathogenic species in genus Yersinia is Yersinia enterocolitica, a food-borne zoonotic pathogen that causes enteric infections, mesenteric lymphadenitis, and sometimes sequelae such as reactive arthritis and erythema nodosum. Y. enterocolitica is able to proliferate at 4 C, making it dangerous if contaminated food products are stored under refrigeration. The most common source of Y. enterocolitica is raw pork meat. Microbiological detection of the bacteria from food products is hampered by its slow growth rate as other bacteria overgrow it. Bacteriophages can be exploited in several ways to increase food safety with regards to contamination by Y. enterocolitica. For example, Yersinia phages could be useful in keeping the contamination of food products under control, or, alternatively, the specificity of the phages could be exploited in developing rapid and sensitive diagnostic tools for the identification of the bacteria in food products. In this review, we will discuss the present state of the research on these topics.

Gold-catalyzed glycosylation in the synthesis of complex carbohydrate-containing natural products

Gold(i)- and gold(iii)-catalyzed glycosylation reactions and their application in the synthesis of natural glycoconjugates are reviewed.

The uniform structure of O-polysaccharides isolated from Dickeya solani strains of different origin

O-polysaccharides were isolated from lipopolysaccharides obtained from four different strains of plant pathogenic bacteria belonging to the species Dickeya solani: two of them were isolated in Poland (IFB0099 and IFB0158), the third in Germany (IFB0223) and the last one, D. solani Type Strain IPO2222, originated from the Netherlands. In addition, the O-polysaccharide of a closely related species D. dadantii strain 3937 was isolated. The purified polysaccharides of the five strains were analyzed using NMR spectroscopy and chemical methods. Sugar and methylation analyses, including absolute configuration assignment, together with NMR data revealed that all O-polysaccharides tested are homopolymers of 6-deoxy-d-altrose (d-6dAlt) the following structure: →2)-β-d-6dAltp-(1→.

DTDP-rhamnosyl transferase RfbF, is a newfound receptor-related regulatory protein for phage phiYe-F10 specific for Yersinia enterocolitica serotype O:3

Bacteriophages and their hosts are continuously engaged in evolutionary competition. Here we isolated a lytic phage phiYe-F10 specific for Yersinia enterocolitica serotype O:3. We firstly described the phage receptor was regulated by DTDP-rhamnosyl transferase RfbF, encoded within the rfb cluster that was responsible for the biosynthesis of the O antigens. The deletion of DTDP-rhamnosyl transferase RfbF of wild type O:3 strain caused failure in phiYe-F10 adsorption; however, the mutation strain retained agglutination with O:3 antiserum; and complementation of its mutant converted its sensitivity to phiYe-F10. Therefore, DTDP-rhamnosyl transferase RfbF was responsible for the phage infection but did not affect recognition of Y. enterocolitica O:3 antiserum. Further, the deletions in the putative O-antigen biosynthesis protein precursor and outer membrane protein had no effect on sensitivity to phiYe-F10 infection. However, adsorption of phages onto mutant HNF10-ΔO-antigen took longer time than onto the WT, suggesting that deletion of the putative O-antigen biosynthesis protein precursor reduced the infection efficiency.

Interaction of human mannose-binding lectin (MBL) with Yersinia enterocolitica lipopolysaccharide

The lipopolysaccharide (LPS) is involved in the interaction between Gram-negative pathogenic bacteria and host. Mannose-binding lectin (MBL), complement-activating soluble pattern-recognition receptor targets microbial glycoconjugates, including LPS. We studied its interactions with a set of Yersinia enterocolitica O:3 LPS mutants. The wild-type strain LPS consists of lipid A (LA) substituted with an inner core oligosaccharide (IC) which in turn is substituted either with the O-specific polysaccharide (OPS) or the outer core hexasaccharide (OC), and sometimes also with the enterobacterial common antigen (ECA). The LPS mutants produced truncated LPS, missing OPS, OC or both, or, in addition, different IC constituents or ECA. MBL bound to LA-IC, LA-IC-OPS and LA-IC-ECA but not LA-IC-OC structures. Moreover, LA-IC substitution with both OPS and ECA prevented the lectin binding. Sequential truncation of the IC heptoses demonstrated that the MBL targets the IC heptose region. Furthermore, microbial growth temperature influenced MBL binding; binding was stronger to bacteria grown at room temperature (22°C) than to bacteria grown at 37°C. In conclusion, our results demonstrate that MBL can interact with Y. enterocolitica LPS, however, the in vivo significance of that interaction remains to be elucidated.

Bacterial cell surface structures in Yersinia enterocolitica

Yersinia enterocolitica is a widespread member of the family of Enterobacteriaceae that contains both non-virulent and virulent isolates. Pathogenic Y. enterocolitica strains, especially belonging to serotypes O:3, O:5,27, O:8 and O:9 are etiologic agents of yersiniosis in animals and humans. Y. enterocolitica cell surface structures that play a significant role in virulence have been subject to many investigations. These include outer membrane (OM) glycolipids such as lipopolysaccharide (LPS) and enterobacterial common antigen (ECA) and several cell surface adhesion proteins present only in virulent Y. enterocolitica, i.e., Inv, YadA and Ail. While the yadA gene is located on the Yersinia virulence plasmid the Ail, Inv, LPS and ECA are chromosomally encoded. These structures ensure the correct architecture of the OM, provide adhesive properties as well as resistance to antimicrobial peptides and to host innate immune response mechanisms.

Synthesis of lipopolysaccharide O-antigens by ABC transporter-dependent pathways

The O-polysaccharide (O-PS; O-antigen) of bacterial lipopolysaccharides is made up of repeating units of one or more sugar residues and displays remarkable structural diversity. Despite the structural variations, there are only three strategies for O-PS assembly. The ATP-binding cassette (ABC)-transporter-dependent mechanism of O-PS biosynthesis is widespread. The Escherichia coli O9a and Klebsiella pneumoniae O2a antigens provide prototypes, which are distinguished by the fine details that link glycan polymerization and chain termination at the cytoplasmic face of the inner membrane to its export via the ABC transporter. Here, we describe the current understanding of these processes. Since glycoconjugate assembly complexes that utilize an ABC transporter-dependent pathway are widespread among the bacterial kingdom, the models described here are expected to extend beyond O-PS biosynthesis systems.

Identification of distinct lipopolysaccharide patterns among Yersinia enterocolitica and Y. enterocolitica-like bacteria

The lipopolysaccharide (LPS) of strains representing various serotypes of Yersinia enterocolitica and Y. enterocolitica-like bacteria was studied by deoxycholate-PAGE and silver staining analysis. Four main types of LPS were detected based on the O-polysaccharide (O-PS): (i) LPS with homopolymeric O-PS, (ii) LPS with ladder-forming heteropolymeric O-PS, (iii) LPS with single-length O-PS, and (iv) semi-rough LPS without O-PS. Within the first three types, several subvariants were detected. Selected serotypes representing all above LPS types are sensitive to bacteriophage φR1-37 indicating that they share the phage receptor, a hexasaccharide called outer core in Y. enterocolitica O:3. Whereas phage φR1-37-resistant mutants of homopolymeric O-PS have lost only the outer core, those of ladder-forming or single-length O-PS have lost also the O-PS suggesting that in the latter ones the outer core is bridging between O-PS and lipid A-core. This work forms a basis of further structural, biochemical and genetic studies of these LPSs.

Apolipoprotein A-I exerts bactericidal activity against Yersinia enterocolitica serotype O:3

Apolipoprotein A-I (apoA-I), the main protein component of high density lipoprotein (HDL), is well recognized for its antiatherogenic, antioxidant, and antiinflammatory properties. Here, we report a novel role for apoA-I as a host defense molecule that contributes to the complement-mediated killing of an important gastrointestinal pathogen, Gram-negative bacterium Yersinia enterocolitica. We specifically show that the C-terminal domain of apoA-I is the effector site providing the bactericidal activity. Although the presence of the lipopolysaccharide O-antigen on the bacterial surface is absolutely required for apoA-I to kill the bacteria, apoA-I does not interact with the bacteria directly. To the contrary, exposure of the bacteria by serum proteins triggers apoA-I deposition on the bacterial surface. As our data show that both purified lipid-free and HDL-associated apoA-I displays anti-bacterial potential, apoA-I mimetic peptides may be a promising therapeutic agent for the treatment of certain Gram-negative infections.

ABC transporters involved in export of cell surface glycoconjugates

Complex glycoconjugates play critical roles in the biology of microorganisms. Despite the remarkable diversity in glycan structures and the bacteria that produce them, conserved themes are evident in the biosynthesis-export pathways. One of the primary pathways involves representatives of the ATP-binding cassette (ABC) transporter superfamily. These proteins are responsible for the export of a wide variety of cell surface oligo- and polysaccharides in both Gram-positive and Gram-negative bacteria. Recent investigations of the structure and function of ABC transporters involved in the export of lipopolysaccharide O antigens have revealed two fundamentally different strategies for coupling glycan polymerization to export. These mechanisms are distinguished by the presence (or absence) of characteristic nonreducing terminal modifications on the export substrates, which serve as chain termination and/or export signals, and by the presence (or absence) of a discrete substrate-binding domain in the nucleotide-binding domain polypeptide of the ABC transporter. A bioinformatic survey examining ABC exporters from known oligo- and polysaccharide biosynthesis loci identifies conserved nucleotide-binding domain protein families that correlate well with themes in the structures and assembly of glycans. The familial relationships among the ABC exporters generate hypotheses concerning the biosynthesis of structurally diverse oligo- and polysaccharides, which play important roles in the biology of bacteria with different lifestyles.

Characterization and biological role of the O-polysaccharide gene cluster of Yersinia enterocolitica serotype O:9

Yersinia enterocolitica serotype O:9 is a gram-negative enteropathogen that infects animals and humans. The role of lipopolysaccharide (LPS) in Y. enterocolitica O:9 pathogenesis, however, remains unclear. The O:9 LPS consists of lipid A to which is linked the inner core oligosaccharide, serving as an attachment site for both the outer core (OC) hexasaccharide and the O-polysaccharide (OPS; a homopolymer of N-formylperosamine). In this work, we cloned the OPS gene cluster of O:9 and identified 12 genes organized into four operons upstream of the gnd gene. Ten genes were predicted to encode glycosyltransferases, the ATP-binding cassette polysaccharide translocators, or enzymes required for the biosynthesis of GDP-N-formylperosamine. The two remaining genes within the OPS gene cluster, galF and galU, were not ascribed a clear function in OPS biosynthesis; however, the latter gene appeared to be essential for O:9. The biological functions of O:9 OPS and OC were studied using isogenic mutants lacking one or both of these LPS parts. We showed that OPS and OC confer resistance to human complement and polymyxin B; the OPS effect on polymyxin B resistance could be observed only in the absence of OC.

The biosynthesis and biological role of lipopolysaccharide O-antigens of pathogenic Yersiniae

Lipopolysaccharide (LPS) is the major component of the outer leaflet of the outer membrane of Gram-negative bacteria. The LPS molecule is composed of two biosynthetic entities: the lipid A--core and the O-polysaccharide (O-antigen). Most biological effects of LPS are due to the lipid A part, however, there is an increasing body of evidence indicating that O-antigen (O-ag) plays an important role in effective colonization of host tissues, resistance to complement-mediated killing and in the resistance to cationic antimicrobial peptides that are key elements of the innate immune system. In this review, we will discuss: (i) the work done on the genetics and biosynthesis of the O-ags in the genus Yersinia; (ii) the role of O-ag in virulence of these bacteria; (iii) the work done on regulation of the O-ag gene cluster expression and; (iv) the impact that the O-ag expression has on other bacterial surface and membrane components.

Topological and functional characterization of WbpM, an inner membrane UDP-GlcNAc C6 dehydratase essential for lipopolysaccharide biosynthesis in Pseudomonas aeruginosa

WbpM is essential for the biosynthesis of B-band lipopolysaccharide (LPS) in many serotypes of Pseudomonas aeruginosa. Homologues that can functionally complement a wbpM null mutant and that are also necessary for virulence have been identified in numerous pathogenic bacteria. WbpM and most of its homologues are large membrane proteins, which has long hampered the elucidation of their biochemical function. This paper describes the detailed characterization of WbpM using both in vivo and in vitro approaches. LacZ and PhoA fusion experiments showed that WbpM was anchored to the inner membrane via four N-terminal transmembrane domains, whereas the C-terminal catalytic domain resided in the cytoplasm. Although the membrane domains did not have any catalytic activity, complementation experiments suggested that they were important for the polymerization of high-molecular-weight B-band LPS. The biochemical characterization of a soluble truncated form of WbpM, His-S262, showed that WbpM was a C6 dehydratase specific for UDP-GlcNAc. It exhibited unusual low temperature (25-30 degrees C) and high pH (pH 10) optima. Although WbpM possessed an altered catalytic triad composed of SMK as opposed to SYK commonly found in other dehydratases, its catalysis was very efficient, with a kcat of 168 min(-1) and a kcat/Km of 58 mM(-1) min(-1). These unusual physico-kinetic properties suggested a potentially different mechanism of C6 dehydration for WbpM and its large homologues. His-S262 is now a precious tool for further structure-function studies.

Novel variation of lipid A structures in strains of different Yersinia species

The Yersinia genus includes human and animal pathogens (plague, enterocolitis). The fine structures of the endotoxin lipids A of seven strains of Yersinia enterocolitica, Yersinia ruckeri and Yersinia pestis were determined and compared using mass spectrometry. These lipids differed in secondary acylation at C-2': this was dodecanoic acid (C(12)) for two strains of Y. enterocolitica and Y. ruckeri, tetradecanoic acid (C(14)) in two other Y. enterocolitica and hexadecenoic acid (C(16:1)) in Y. pestis. The enterocolitica lipids having a mass identical to that of Escherichia coli were found to be structurally different. The results supported the idea of a relation between membrane fluidity and environmental adaptability in Yersinia.

The lipopolysaccharide outer core of Yersinia enterocolitica serotype O:3 is required for virulence and plays a role in outer membrane integrity

Lipopolysaccharide (LPS) of Yersinia enterocolitica O:3 has an inner core linked to both the O-antigen and to an outer core hexasaccharide that forms a branch. The biological role of the outer core was studied using polar and non-polar mutants of the outer core biosynthetic operon. Analysis of O-antigen- and outer core-deficient strains suggested a critical role for the outer core in outer membrane properties relevant in resistance to antimicrobial peptides and permeability to hydrophobic agents, and indirectly relevant in resistance to killing by normal serum. Wild-type bacteria but not outer core mutants killed intragastrically infected mice, and the intravenous lethal dose was approximately 10(4)-fold higher for outer core mutants. After intragastric infection, outer core mutants colonized Peyer's patches and invaded mesenteric lymph nodes, spleen and liver, and induced protective immunity against wild-type bacteria. In mice co-infected intragastrically with an outer core mutant-wild type mixture, both strains colonized Peyer's patches similarly during the first 2 days, but the mutant was much less efficient in colonizing deeper organs and was cleared faster from Peyer's patches. The results demonstrate that outer core is required for Y. enterocolitica O:3 full virulence, and strongly suggest that it provides resistance against defence mechanisms (most probably those involving bactericidal peptides).

Yersinia pseudotuberculosis and Yersinia pestis show increased outer membrane permeability to hydrophobic agents which correlates with lipopolysaccharide acyl-chain fluidity

The hydrophobic probe N-phenyl-1-naphthylamine accumulated less in non-pathogenic Yersinia spp. and non-pathogenic and pathogenic Yersinia enterocolitica than in Yersinia pseudotuberculosis or Yersinia pestis. This was largely due to differences in the activity of efflux systems, but also to differences in outer membrane permeability because uptake of the probe in KCN/arsenate-poisoned cells was slower in the former group than in Y. pseudotuberculosis and Y. pestis. The probe accumulation rate was higher in Y. pseudotuberculosis and Y. pestis grown at 37 degrees C than at 26 degrees C and was always highest in Y. pestis. These yersiniae had LPSs with shorter polysaccharides than Y. enterocolitica, particularly when grown at 37 degrees C. Gel<-->liquid-crystalline phase transitions (Tc 28-31 degrees C) were observed in LPS aggregates of Y. enterocolitica grown at 26 and 37 degrees C, with no differences between non-pathogenic and pathogenic strains. Y. pseudotuberculosis and Y. pestis LPSs showed no phase transitions and, although the fluidity of LPSs of Y. pseudotuberculosis and Y. enterocolitica grown at 26 degrees C were close below the Tc of the latter, they were always in a more fluid state than Y. enterocolitica LPS. Comparison with previous studies of Salmonella choleraesuis subsp. choleraesuis serotype minnesota rough LPS showed that the increased fluidity and absence of transition of Y. pseudotuberculosis and Y. pestis LPSs cannot be explained by their shorter polysaccharides and suggested differences at the lipid A/core level. It is proposed that differences in LPS-LPS interactions and efflux activity explain the above observations and reflect the adaptation of Yersinia spp. to different habitats.

Passive immunization with monoclonal antibodies specific for lipopolysaccharide (LPS) O-side chain protects mice against intravenous Yersinia enterocolitica serotype O:3 infection

Passive immunization with monoclonal antibodies specific for the lipopolysaccharide (LPS) O-side chain protected mice against intravenously given lethal doses of Yersinia enterocolitica O:3 bacteria. On the other hand, passive immunization with monoclonal antibody specific for the LPS core oligosaccharide did not protect mice. Neither antibody was able to protect mice against orally given lethal doses of bacteria. These results indicate that the O-side chain functions as an important antigenic structure during infection, and that immunity to it probably offer protection also in the in vivo situation.

The gene cluster directing O-antigen biosynthesis in Yersinia enterocolitica serotype 0:8: identification of the genes for mannose and galactose biosynthesis and the gene for the O-antigen polymerase

The rfb gene cluster of Yersinia enterocolitica serotype O:8 (YeO8) strain 8081-c was cloned by cosmid cloning. Restriction mapping, deletion analysis and transposon mutagenesis showed that about 19 kb of the cloned DNA is essential for the synthesis and expression of the YeO8 O-side-chain in Escherichia coli. Deletion analysis generated a derivative that expressed semi-rough LPS, a phenotype typical of an rfc mutant lacking the O-antigen polymerase. The deletions and transcomplementation experiments allowed localization of the rfc gene to the 3'-end of the rfb gene cluster. The deduced YeO8 Rfc did not share significant amino acid sequence similarity with any other protein, but its amino acid composition and hydrophobicity profile are similar to those of identified Rfc proteins. In addition, the codon usage of the rfc gene is similar to other rfc genes. Nucleotide sequence analysis identified three other genes upstream of rfc. Two of the gene products showed 60-70% identity to the RfbM and RfbK proteins that are biosynthetic enzymes for the GDPmannose pathway of enterobacteria. The third gene product was about 50-80% identical to the bacterial GalE protein, UDPglucose 4-epimerase, which catalyses the epimerization of UDPglucose to UDPgalactose. Since mannose and galactose are both present in the YeO8 O-antigen repeat unit, the above three genes are likely to belong to the rfb gene cluster. A gene similar to the gsk gene downstream of rfc, and genes similar to adk and hemH upstream of the rfb gene cluster, were recognized. Thus the rfb gene cluster of YeO8 is located between the adk-hemH and gsk loci, and the order is adk-hemH-rfb-rfc-gsk in the chromosome. Also in other Yersinia spp., the locus downstream of the hemH gene is occupied by gene clusters associated with LPS biosynthesis.

The inner core region of Yersinia enterocolitica Ye75R (0:3) lipopolysaccharide

The inner-core region of the lipopolysaccharide of an UDPGalNAc-4-epimerase-deficient mutant of Yersinia enterocolitica 0:3, designated as Ye75R, was investigated using methylation analysis, 1D-13C-NMR and 2D-13C-NMR and 1H-NMR, as well as 31P-NMR, fast-atom-bombardment mass spectrometry (FAB MS) and FAB MS/MS in positive and negative modes. The isolated core heptasaccharide (OS) was composed of 2 units D-glucose, 3 units LD-heptose and 1 unit each of DD-heptose and 3-deoxy-D-manno-octulosonic acid. Methylation analysis indicated that OS was highly branched with terminal location of the two glucoses and the DD-heptose unit, which was partially (to about 40%) phosphorylated at C7. These combined studies allowed us to formulate the structure of the inner core region as shown in Scheme 1. The substitution of the 7-position of the terminally linked DD-heptose unit by phosphate could be recognized by MS characterization of permethylated DD-heptose-7-phosphate (alditol acetate) and the extent of the substitution by the ratio of the two well separated 1H signals of DD-heptose in 500-MHz 1H-NMR. Negative FAB MS of OS also indicated the presence of smaller amounts of two hexasaccharides, differing from OS in lacking either one terminal unit of D-glucose or of the terminal DD-heptose, and additionally of a pentasaccharide lacking two heptosyl units, namely the terminal DD-heptose and and the subterminal LD-heptose. The presence of the smaller oligosaccharides in the OS fraction was also recognized by the methylation analysis.

Genetic organization and sequence of the rfb gene cluster of Yersinia enterocolitica serotype O:3: similarities to the dTDP-L-rhamnose biosynthesis pathway of Salmonella and to the bacterial polysaccharide transport systems

The Yersinia enterocolitica O:3 lipopolysaccharide O-antigen is a homopolymer of 6-deoxy-L-altrose. The cloned rfb region was sequenced, and 10 open reading frames were identified. Transposon mutagenesis, deletion analysis and transcomplementation experiments showed that eight of the genes, organized into two operons, rfbABC and rfbDEFGH, are essential for O-antigen synthesis. Functional tandem promoters were identified upstream of both operons. Of the deduced polypeptides RfbA, RfbF and RfbG were similar to Salmonella proteins involved in the dTDP-L-rhamnose biosynthesis. Rhamnose and 6-deoxy-L-altrose are C3-epimers suggesting that analogous pathways function in their biosynthesis. RfbD and RfbE were similar to capsular polysaccharide export proteins, e.g. KpsM and KpsT of Escherichia coli. This and transposon mutagenesis showed that RfbD and RfbE function as O-antigen exporters.

Yersinia enterocolitica lipopolysaccharide: genetics and virulence

The O side chain (O antigen) of the lipopolysaccharide of Yersinia enterocolitica serotype O:3 has been shown to be a virulence factor. The genes directing the biosynthesis of the O antigen have been cloned, sequenced and characterized. Like the expression of most of the virulence factors of Y. enterocolitica, O-antigen expression is temperature regulated.

Factors promoting acute and chronic diseases caused by yersiniae

The experimental system constructed with the medically significant yersiniae provides a powerful basic model for comparative study of factors required for expression of acute versus chronic disease. The system exploits the close genetic similarity between Yersinia pestis, the etiological agent of bubonic plague, and enteropathogenic Yersinia pseudotuberculosis and Yersinia enterocolitica. Y. pestis possesses three plasmids, of which one, shared by the enteropathogenic species, mediates a number of virulence factors that directly or indirectly promote survival within macrophages and immunosuppression. The two remaining plasmids are unique and encode functions that promote acute disease by enhancing bacterial dissemination in tissues and resistance to phagocytosis by neutrophils and monocytes. These properties are replaced in the enteropathogenic yersiniae by host cell invasins and an adhesin which promote chronic disease; the latter are cryptic in Y. pestis. Additional distinctions include specific mutational losses in Y. pestis which result in loss of fitness in natural environments plus gain of properties that facilitate transmission and infection via fleabite.

Immunological characterization of Yersinia enterocolitica O:9 and O:3 LPS antigens by monoclonal antibodies

LPS-specific monoclonal antibodies induced against Y. enterocolitica serotype O:9 bacteria and against Y. enterocolitica O:3 were used in a comparative study to characterize the O:9 and O:3 LPS. Yersinia bacteria grown at 22 degrees C and 37 degrees C and LPS preparations thereof were tested. SDS-PAGE, Western blot analysis and adsorption procedures revealed that LPS of Y. enterocolitica O:9 differed from that of Y. enterocolitica O:3 in: (i) its repeating LPS O-side-chain sugar, (ii) its shorter length of the LPS O-side-chain and (iii) its failure to show temperature-dependent variation in the length of O-side-chains.

Identification and determination of absolute and anomeric configurations of the 6-deoxyaltrose residue found in polysialoglycoprotein of Salvelinus leucomaenis pluvius eggs. The first demonstration of the presence of a 6-deoxyhexose other than fucose in glycoprotein

An oligosaccharide alditol, dHex-GalNAc-Gal-Gal-GalNAcol, has been isolated from polysialoglycoprotein, which was derived from the unfertilized eggs of Savelinus leucomaenis pluvius (a salmonid fish, Iwana in Japanese), by alkaline borohydride treatment followed by exhaustive digestion with sialidase. First, the structure of the terminal dHex residue in the above pentasaccharide has been assigned as 6-deoxyaltrose (= dAlt in pyranoid form) by a combination of structural methods (GLC, TLC, mass spectrometry, and 400-MHz 1H-NMR spectroscopy). The occurrence of a 6-deoxyhexose other than L-fucose in glycoprotein has not been previously reported. Next, the absolute configuration of this unusual sugar residue has been assigned as D on the basis of the exciton-splitting study of tris-p-bromobenzoate derivatives of methyl 6-deoxyaltrosides. The usefullness of this circular dichroic exciton-splitting method in the determination of the absolute configuration of carbohydrate components, only available in minute amounts, is emphasized. The anomeric configuration of the glycosidic linkage of the D-altropyranosyl residue was deduced from 400-MHz 1H NMR spectroscopy. The 6-deoxy-beta-D-altropyranosyl residue thus established has the same configuration as alpha-L-fucose but with the C-5 methyl group inverted, suggesting that the biosynthetic incorporation of D-dAlt parallels that of L-fucose, and a possible pathway is also considered.

Structural studies on O-specific polysaccharides of lipopolysaccharides from Yersinia enterocolitica serovars O:5 and O:5,27

Lipopolysaccharides of Yersinia enterocolitica serovars O:5 and O:5,27 were shown to have a similar sugar composition, consisting of L-rhamnose, D-glucose, D-galactose, D- and L-glycero-D-manno-heptose, 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-galactose, 3-deoxy-D-manno-octulosonate and D-threo-pent-2-ulose (D-xylulose). Partial hydrolysis of lipopolysaccharides with acetic acid produced rhamnans with the following repeating unit: ----3)-L-Rha rho(alpha 1----3)-L-Rha rho(alpha 1----3)-L-Rha rho(beta 1----. 13C-NMR and methylation studies of the lipopolysaccharides gave the following structure for the repeating unit of the two O-specific polysaccharides: ----3)-L-Rha rho(alpha 1----3)-L-Rha rho(alpha 1----3)-L-Rha rho(beta 1----. (formula; see text)

Structural studies on O-specific polysaccharides of lipopolysaccharides from Yersinia enterocolitica serovars O:1,2a,3, O:2a,2b,3 and O:3

Lipopolysaccharides from Yersinia enterocolitica serovars O:1,2a,3, O:2a,2b,3 and O:3 have been isolated and characterized. 6-Deoxy-L-altrose residues were shown to be the main constituents of lipopolysaccharides isolated in addition to residues of L-rhamnose, D-glucose, D-galactose, 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-galactose, D-glycero-D-manno-heptose and L-glycero-D-manno-heptose, 3-deoxy-D-manno-octulosonic acid being minor components of sugar chains. Mild hydrolysis of lipopolysaccharides with acetic acid furnished O-specific polysaccharides, which are composed of 6-deoxy-L-altrose. Using 13C-NMR spectroscopy and methylation data, the structural features of backbones have been elucidated as follows: ----2)-6d-L-Altp(beta 1----2)-6d-L-Altp(beta 1----3)-6d-L-Altp)(beta 1----for serovars O:1,2a,3 and O:2a,2b,3;----2)-6d-L-Altp(beta 1----for serovar O:3. In addition, O-polysaccharide of serovar O:2a,2b,3 was found to contain an O-acetyl group at the C-3 position of some 1,2-linked sugar residues.

Vwa+ phenotype of Yersinia enterocolitica

Expression of the Vwa+ phenotype of Yersinia pestis in vitro is known to reflect maximum induction of virulence (or V and W antigens) at 37 degrees C with concomitant restriction of cell division. Both phenomena are potentiated by 20 mM Mg2+ and prevented by cultivation at 26 or 37 degrees C with 2.5 mM Ca2+. We have now compared this classic plasmid-mediated phenotype with those of Vwa+ Yersinia pseudotuberculosis and Yersinia enterocolitica which, unlike Y. pestis, produce ancillary outer membrane peptides unrelated to the V and W antigens. All of 10 wild-type strains of Y. enterocolitica (serotypes O:3, O:4,32, O:8, O:9, O:15, and O:21) exhibited a nutritional requirement for Ca2+ at 37 degrees C and produced significant V antigen. Like Y. pseudotuberculosis, autoagglutination of Vwa+ Y. enterocolitica was dependent upon prior growth at 37 degrees C but was not influenced by Ca2+. Autoagglutination of Y. pestis was never observed. Resistance of Y. enterocolitica to 10% human serum was typically dependent upon prior growth at 37 degrees C, either with or without added Ca2+, and carriage of a Vwa plasmid. In contrast, serum resistance of Y. pseudotuberculosis was temperature but not plasmid dependent and that of Y. pestis was constitutive.

Localization of enterobacterial common antigen in Yersinia enterocolitica by the immunoferritin technique

Rabbits were immunized with the enterobacterial common antigen (ECA)-immunogenic strain Escherichia coli F470. ECA-specific antiserum was obtained by absorbing the resulting antisera with the genetically closely related ECA-negative strain E. coli F1283. These two strains also served as positive and negative controls in the localization study of ECA in Yersinia enterocolitica strain 75, smooth and rough forms (Ye75S and Ye75R), by the indirect immunoferritin technique. Cells of Ye75S grown at 22 degrees C showed no labeling with ferritin after treatment with the ECA-specific antiserum and subsequent ferritin-conjugated goat anti-rabbit antibodies. If the cells were grown at 40 degrees C, however, most of the cells showed weak ferritin labeling. At this higher growth temperature, the lipopolysaccharide of this strain contains less O-specific chains (6-deoxy-L-altrose), as was shown in a previous study. The rough mutant Ye75R, which lacks O-specific chains completely, showed denser labeling with ferritin. These results indicate that ECA on the cell surface of Ye75S is covered by O-specific chains of the lipopolysaccharide if grown at 22 degrees C and is therefore not accessible to ECA antibodies. It becomes accessible, however, when O-chains are lacking (R mutants) or when they are reduced in size or amount (growth at 40 degrees C).