The core region of Proteus mirabilis R110/1959 lipopolysaccharide

Inactivation of the arn operon and loss of aminoarabinose on lipopolysaccharide as the cause of susceptibility to colistin in an atypical clinical isolate of proteus vulgaris

Colistin has become a last-line antibiotic for the treatment of multidrug-resistant bacterial infections; however, resistance to colistin has emerged in recent years. Some bacteria, such as Proteus and Serratia spp., are intrinsically resistant to colistin although the exact mechanism of resistance is unknown. Here we identified the molecular support for intrinsic colistin resistance in Proteus spp. by comparative genomic, transcriptomic and proteomic analyses of colistin-susceptible (CSUR P1868_S) and colistin-resistant (CSUR P1867_R) strains of an atypical Proteus vulgaris. A significant difference in outer membrane glycoside structures in both strains that was corroborated by MALDI-TOF/MS analysis was found, which showed an absence of 4-amino-4-deoxy-l-arabinose (L-Ara4N) in the outer membrane lipid A moiety of the susceptible strain. Comparative genomic analysis with other resistant strains of P. vulgaris available in a local database found a mutation in the arnBCADTEF operon of the susceptible strain. Transcriptomic analysis of genes belonging to the arnBCADTEF operon showed a significant decrease in mRNA expression level of these genes in the susceptible strain, supporting addition of L-Ara4N in the outer membrane lipid A moiety as an explanation for colistin resistance. Insertion of the arnD gene that was suggested to be altered in the susceptible strain by in silico analysis led to a 16-fold increase of colistin MIC in the susceptible strain, confirming its role in colistin resistance in this species. Here we show that constitutive activation of the arn operon and addition of L-Ara4N is the main molecular mechanism of colistin resistance in P. vulgaris.

Detection of human antibodies binding with smooth and rough LPSs from Proteus mirabilis O3 strains S1959, R110, R45

Bacteria of the genus Proteus of the family Enterobacteriaceae are facultative human pathogens responsible mainly for urinary tract and wound infections, bacteremia and the development of rheumatoid arthritis (RA). We have analyzed and compared by ELISA the titer of antibodies in plasmas of healthy individuals and in sera of rheumatoid arthritis patients recognizing a potential host cross-reactive epitope (lysine-galacturonic acid epitopes) present in Proteus lipopolysaccharide (LPS). In our experiments LPSs isolated from two mutants of smooth Proteus mirabilis 1959 (O3), i.e. strains R110 and R45, were used. R110 (Ra type mutant) is lacking the O-specific polysaccharide, but possesses a complete core oligosaccharide, while R45 (Re type) has a reduced core oligosaccharide and contains two 3-deoxy-D-manno-oct-2-ulosonic acid residues and one of 4-amino-4-deoxy-L-arabinopyranose residues. Titer of P. mirabilis S1959 LPS-specific-antibodies increased with the age of blood donors. RA and blood donors' sera contained antibodies against S and Ra and Re type of P. mirabilis O3 LPSs. Antibodies recognizing lysine-galacturonic acid epitopes of O3 LPS were detected by ELISA in some plasmas of healthy individuals and sera of rheumatoid arthritis patients. RA patients antibodies reacting with P. mirabilis S1959 S and R LPSs may indicate a potential role of anti-LPS antibodies in molecular mimicry in RA diseases.

Complement activation by Proteus mirabilis negatively charged lipopolysaccharides

Proteus mirabilis strains are human pathogens responsible for urinary tract infections and bacteremias and may be involved in rheumatoid arthritis. Lipopolysaccharide (LPS, bacterial endotoxin), the major component of the cell wall, is one of the virulence factors of Proteus. In the presented studies, we have investigated complement activation by LPSs isolated from P. mirabilis O10, O23, O30, and O43 strains, which differ in the number of negative COO— groups on their polysaccharide components. Four P. mirabilis strains studied were sensitive to complement-mediated killing, despite complement binding by their LPSs. The optimal complement binding by LPSs was detected in serum with functional assays for both the classical and alternative pathways.

Complement activation in 80% serum by the smooth, uronic acid, and hexosamine containing P. mirabilis LPSs was not critically determined by the structure of their O-chain polysaccharides. One of four LPSs used as a model, P. mirabilis O10 LPS, fragmented C3 in an LPS dose- and time-dependent manner. It was detected by crossed-immunoelectrophoresis and capture ELISA with anti-C3c antibodies. The lower complement activation by O23 LPS correlates with its reduced C3 fragmentation, compared with three other Proteus LPSs studied. Rabbit anti-O antibodies enhanced the complement binding and factor C3 fragmentation by O10, O23, O30, and O43 P. mirabilis LPSs.

Resistance of Serratia marcescens to polymyxin B: a comparative investigation of two S-form lipopolysaccharides obtained from a sensitive and a resistant variant of strain 111

Lipopolysaccharide (LPS) of the polymyxin B (PmB)-sensitive variant of Serratia marcescens smooth-type strain 111 (senLPS) binds significantly more PmB than that of the resistant variant (resLPS), following mild acid hydrolysis this difference is abolished. The main compositional differences between these strains are: (i) the amount of 4-amino-4-deoxy-arabinose (Ara4N); and (ii) the substitution patterns of the phosphate groups. ResLPS contains three times more Ara4N than senLPS, mainly phosphodiesters, whereas senLPS contains mainly (di)-phosphomonoesters. Thus, the senLPS, and the bacterial surface, contain a higher negative charge density. Mild acid hydrolysis decreases the PmB-binding capacity of senLPS and increases that of resLPS. The resulting change in LPS composition was a reduction in the amount of phosphate (about 40%) and a loss of nearly all the Ara4N residues, from both LPS. Mild alkaline hydrolysis removes Ara4N from both LPS, and the hydrolysate contains Ara4N-phosphate, but no Ara4N-(1 →8)-Kdo was detected. The results suggest that the 4'-phosphate of lipid A mediates the binding of PmB, whereas its substitution by Ara4N prevents it.

Human hemoglobin increases the biological activity of bacterial lipopolysaccharides in activation of Limulus amebocyte lysate and stimulation of tissue factor production by endothelial cells in vitro

Previous studies have demonstrated that hemoglobin (Hb) and bacterial endotoxin (lipopolysaccharide, LPS) form stable complexes and result in disaggregation of macromolecular LPS. To examine the effect of complex formation on LPS biological activity, we investigated the ability of Hb to alter LPS-induced activation of the coagulation cascade of Limulus amebocyte lysate (LAL) and expression of tissue factor from human endothelial cells. Both native HbAo and derivatized (covalently cross-linked) hemoglobin resulted in prominent enhancement of LAL activation and endothelial cell tissue factor production by Proteus mirabilis LPS. No substantial differences were observed between the enhancement effect of Hb on P. mirabilis smooth and rough LPS, indicating a dominant role for the lipid A component of LPS. Rough (Re) Salmonella min nesota 595 LPS also demonstrated both enhanced activation of LAL and stimulation of endothelial cell tissue factor in the presence of Hb. In contrast, neither lipid A nor singly dephosphorylated or partially deacylated Re LPS manifested significant enhancement of LAL activation by Hb, and partially deacylated Re LPS showed no enhancement of endothelial cell tissue factor by Hb. These results suggest that the Kdo moieties, as well as the phosphate residues and fatty acyl moieties of lipid A, may be involved in the interaction of Hb with LPS. Comparison of Hb with other endotoxin binding proteins for ability to cause enhancement of LPS biological activity demonstrated more prominent enhancement with lipopolysaccharide binding protein (LBP) than that observed with Hb, lesser enhancement with albumin, and no enhancement effect with IgG or transferrin.

The sugar 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) as a characteristic component of bacterial endotoxin — a review of its biosynthesis, function, and placement in the lipopolysaccharide core

The sugar 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) is a characteristic component of bacterial lipopolysaccharide (LPS, endotoxin). It connects the carbohydrate part of LPS with C6 of glucosamine or 2,3-diaminoglucose of lipid A by acid-labile α-ketosidic linkage. The number of Kdo units present in LPS, the way they are connected, and the occurrence of other substituents (P, PEtn, PPEtn, Gal, or β-l-Ara4N) account for structural diversity of the inner core region of endotoxin. In a majority of cases, Kdo is crucial to the viability and growth of bacterial cells. In this paper, the biosynthesis of Kdo and the mechanism of its incorporation into the LPS structure, as well as the location of this unique component in the endotoxin core structures, have been described.

Proteus sp. – an opportunistic bacterial pathogen – classification, swarming growth, clinical significance and virulence factors

The genus Proteus belongs to the Enterobacteriaceae family, where it is placed in the tribe Proteeae, together with the genera Morganella and Providencia. Currently, the genus Proteus consists of five species: P. mirabilis, P. vulgaris, P. penneri, P. hauseri and P. myxofaciens, as well as three unnamed Proteus genomospecies. The most defining characteristic of Proteus bacteria is a swarming phenomenon, a multicellular differentiation process of short rods to elongated swarmer cells. It allows population of bacteria to migrate on solid surface. Proteus bacteria inhabit the environment and are also present in the intestines of humans and animals. These microorganisms under favorable conditions cause a number of infections including urinary tract infections (UTIs), wound infections, meningitis in neonates or infants and rheumatoid arthritis. Therefore, Proteus is known as a bacterial opportunistic pathogen. It causes complicated UTIs with a higher frequency, compared to other uropathogens. Proteus infections are accompanied by a formation of urinary stones, containing struvite and carbonate apatite. The virulence of Proteus rods has been related to several factors including fimbriae, flagella, enzymes (urease - hydrolyzing urea to CO2 and NH3, proteases degrading antibodies, tissue matrix proteins and proteins of the complement system), iron acqusition systems and toxins: hemolysins, Proteus toxin agglutinin (Pta), as well as an endotoxin - lipopolysaccharide (LPS). Proteus rods form biofilm, particularly on the surface of urinary catheters, which can lead to serious consequences for patients. In this review we present factors involved in the regulation of swarming phenomenon, discuss the role of particular pathogenic features of Proteus spp., and characterize biofilm formation by these bacteria.

ECA-immunogenicity of Proteus mirabilis strains

Introduction

Bacteria of the genus Proteus are opportunistic pathogens and cause mainly urinary tract infections. They also play a role in the pathogenesis of reactive arthritis (RA). Patients suffering from Yersinia-triggered RA often carry high titers of antibodies specific to enterobacterial common antigen (ECA). The immunogenicity of ECA has not received much attention thus far and studies have focused mainly on the ECA of Escherichia coli and Yersinia enterocolitica. In this paper the ECA-immunogenicity of Proteus mirabilis is elucidated using two wild-type strains (S1959 and O28) as well as their rough (R) derivative strains R110/1959, which expresses lipopolysaccharide (LPS) with a full core, and R4/O28, which expresses LPS with only an inner core.

Materials and Methods

Rabbit polyclonal antisera were produced by immunization with boiled suspensions of the four P. mirabilis strains. The antisera were tested for the presence of antibodies specific to ECA by Western blotting using glycerophospholipid- linked ECA (ECA_PG) of Salmonella montevideo as antigen. Lipopolysaccharide (LPS) was isolated from the four strains by the hot phenol/water procedure in which ECA_PG is co-extracted with LPS and by the phenol/chloroform/petroleum ether extraction that results in the isolation of LPS and/or LPS-linked ECA (ECA_LPS) free of ECA_PG. The LPS preparations were tested for the presence of ECA by Western blotting using ECA-specific antibodies.

Results

The results demonstrated that all four P. mirabilis strains were ECA immunogenic. The rabbit antisera immunized by the four strains all contained ECA-specific antibodies. Analysis of the LPS preparations demonstrated that the P. mirabilis wild-type strains O28 and S1959 and the Ra mutant strain R110/1959 expressed ECA_LPS, suggesting that it induced the anti-ECA antibody responses. Only the presence of ECA_PG could be demonstrated in the Rc mutant strain R4/O28.

Conclusions

These results therefore suggest that, similar to E. coli, LPS with a full core is also required as the acceptor of ECA for P. mirabilis strains to produce ECA_LPS. Since ECA_PG is not immunogenic unless combined with some proteins, it is likely that ECA_PG-protein complexes formed during the intravenous immunization with the Rc mutant strain R4/O28.

Lipopolysaccharides possessing two L-glycero-D-manno-heptopyranosyl-alpha -(1-->5)-3-deoxy-D-manno-oct-2-ulopyranosonic acid moieties in the core region. The structure of the core region of the lipopolysaccharides from Burkholderia caryophylli

The carbohydrate backbone of the core-lipid A region was characterized from the lipopolysaccharides (LPSs) of the plant-pathogenic bacterium Burkholderia caryophylli. For the first time, the presence of two moieties of l-glycero-d-manno-heptopyranosyl-alpha-(1-->5)-3-deoxy-d-manno-oct-2-ulopyranosonic acid was identified in a core region, which is of particular interest with regard to the biosynthesis of this and of LPSs in general. The LPSs of B. caryophylli were degraded by mild hydrazinolysis (de-O-acylation), treatment with 48% aqueous HF at 4 degrees C (cleavage of phosphate groups and destruction of the O-specific polysaccharides), reduction with NaBH4, and de-N-acylation utilizing hot KOH. The major oligosaccharide representing the carbohydrate backbone of the core region and lipid A was isolated by high-performance anion-exchange chromatography. Its analysis employing compositional and methylation analyses, matrix-assisted laser desorption/ionization mass spectrometry, and (1)H and (13)C NMR spectroscopy applying various one-dimensional and two-dimensional experiments identified the following structure. Structure I All sugars are pyranoses and alpha-linked, if not stated otherwise. Hep is l-glycero-d-manno-heptose, Kdo is 3-deoxy-d-manno-oct-2-ulosonic acid.

Biosynthesis of nucleotide-activated D-glycero-D-manno-heptose

The glycan chain repeats of the S-layer glycoprotein of Aneurinibacillus thermoaerophilus DSM 10155 contain d-glycero-d-manno-heptose, which has also been described as constituent of lipopolysaccharide cores of Gram-negative bacteria. The four genes required for biosynthesis of the nucleotide-activated form GDP-d-glycero-d-manno-heptose were cloned, sequenced, and overexpressed in Escherichia coli, and the corresponding enzymes GmhA, GmhB, GmhC, and GmhD were purified to homogeneity. The isomerase GmhA catalyzed the conversion of d-sedoheptulose 7-phosphate to d-glycero-d-manno-heptose 7-phosphate, and the phosphokinase GmhB added a phosphate group to form d-glycero-d-manno-heptose 1,7-bisphosphate. The phosphatase GmhC removed the phosphate in the C-7 position, and the intermediate d-glycero-alpha-d-manno-heptose 1-phosphate was eventually activated with GTP by the pyrophosphorylase GmhD to yield the final product GDP-d-glycero-alpha-d-manno-heptose. The intermediate and end products were analyzed by high performance liquid chromatography. Nuclear magnetic resonance spectroscopy was used to confirm the structure of these substances. This is the first report of the biosynthesis of GDP-d-glycero-alpha-d-manno-heptose in Gram-positive organisms. In addition, we propose a pathway for biosynthesis of the nucleotide-activated form of l-glycero-d-manno-heptose.

The structure of the core part of Proteus penneri strain 16 lipopolysaccharide

The structure of the carbohydrate backbone of the lipid A-core region of the lipopolysaccharide (LPS) from Proteus penneri strain 16 was determined using NMR and chemical analysis of the core oligosaccharide, obtained by mild acid hydrolysis of the LPS, and of the products of alkaline deacylation of the LPS: formula [see text]. Incomplete substitution is indicated by bold italics. All sugars are in the pyranose form, alpha-Hep is the residue of L-glycero-alpha-D-manno-Hep, alpha-DD-Hep is the residue of D-glycero-alpha-D-manno-Hep, Bu is the (R)-3-hydroxybutyryl residue.

The structure of the carbohydrate backbone of core-lipid A region ofthe lipopolysaccharides from Proteus mirabilis wild-type strain S1959 (serotype O3) and its Ra mutant R110/1959

The following structure of core-lipid A region of the lipopolysaccharide (LPS) from Proteus mirabilis strain 1959 (serotype O3) and its rough mutant R110/1959 (Proteus type II core) was determined using NMR and chemical analysis of the core oligosaccharide, obtained by mild acid hydrolysis of LPS, and of the products of alkaline deacylation of the LPS: Incomplete substitutions are indicated by italics. All sugars are in pyranose form, alpha-Hep is the residue Lglycero-alpha-Dmanno-Hep, alpha-DD-Hep is the residue Dglycero-alpha-Dmanno-Hep. The differences with the previously reported structures are discussed.

The structure of the core part of Proteus mirabilis O27 lipopolysaccharide with a new type of glycosidic linkage

The structural assignment of the intact lipopolysaccharide core from Proteus mirabilis O27 has been completed based on a combination of chemical degradation studies, NMR spectroscopy and ES-MS spectroscopy. The overall core structure is as follows: [formula: see text] where all sugars are in the pyranose form except the N-acetylglycosamine residue, Hep refers to L-glycero-alpha-D-manno-heptopyranose and alpha-DDHep to D-glycero-alpha-D-manno-heptopyranose. Bold italics indicate non-stoichiometric substituents. A new type of glycosidic linkage has been discovered wherein a GalNAc residue is linked as an open form acetal to the 4- and 6-positions of a 2-amino-2-deoxygalactopyranose residue. This structural element is abbreviated GaloNAc-4,6-, where the 'o' indicates the open form of the sugar residue.

The structure of the carbohydrate backbone of the core-lipid A region of the lipopolysaccharide from a clinical isolate of Yersinia enterocolitica O:9

Yersinia enterocolitica O:9 strain Ruokola/71-c-PhiR1-37-R possesses mainly rough-type lipopolysaccaride (LPS) and smaller amounts of S-form LPS. Structural analysis of the former is reported here. After deacylation of the LPS, the phosphorylated carbohydrate backbone of the inner core-lipid A region could be isolated by using high-performance anion-exchange chromatography. Its structure was determined by means of compositional and methylation analyses and 1H-, 13C-, and 31P-NMR spectroscopy as: [see text] in which L-alpha-D-Hep is L-glycero-alpha-D-manno-heptopyranose, D-alpha-D-Hep is D-glycero-alpha-D-manno-heptopyranose, and Kdo is 3-deoxy-D-manno-oct-2-ulopyranosonic acid. All hexoses are pyranoses.

Structure and serological specificity of a new acidic O-specific polysaccharide of Proteus vulgaris O45

The following structure of the O-specific polysaccharide (OPS) of Proteus vulgaris O45 lipopolysaccharide (LPS) was established using 1H- and 13C-NMR spectroscopy, including two-dimensional NOESY and H-detected 1H, 13C heteronuclear multiple-quantum coherence ( HMQC) experiments: [structure: see text text] Immunochemical studies, using rabbit polyclonal anti-P. vulgaris O45 serum and LPS, OPS and Smith-degraded OPS of P. vulgaris O45, showed the importance of beta-D-GlcA in manifesting the serological specificity of the O-antigen studied.

Identification of a novel heptoglycan of alpha1-->2-linked D-glycero-D-manno-heptopyranose. Chemical and antigenic structure of lipopolysaccharides from Klebsiella pneumoniae ssp. pneumoniae rough strain R20 (O1-:K20-)

In a preliminary investigation (Süsskind, M., Müller-Loennies, S., Nimmich, W., Brade, H., and Holst, O. (1995) Carbohydr. Res. 269, C1-C7), we identified after deacylation of lipopolysaccharides (LPS) from Klebsiella pneumoniae ssp. pneumoniae rough strain R20 (O1(-):K20(-)) as a major fraction the oligosaccharide,-structure; see text- where Kdo was 3-deoxy-D-manno-oct-2-ulopyranosonic acid and Hepp was manno-heptopyranose. The presence of the threo-hex-4-enuronopyranosyl residue indicated a substituent at O-4 of the second GalA residue linked to O-3 of the second L,D-Hep residue, which had been eliminated by treatment with hot alkali. We now report the complete structure of lipopolysaccharide, which was elucidated by additional characterization of isolated core oligosaccharides and analysis of the lipid A. The substituent at O-4 of the second GalpA is D-GlcpN, which in a fraction of the LPS is substituted at O-6 by three or four residues of D-glycero-D-manno-heptopyranose (D,D-Hepp). The complete carbohydrate backbone of the LPS is as follows, -structure; see text- (L-glycero-D-manno-heptopyranose; L,D-Hepp), where all hexoses possess the D-configuration. Sugars marked with an asterisk are present in nonstoichiometric amounts. The structure is unique with regard to the presence of an alpha1-->2-linked D-glycero-D-manno-heptoglycan (oligosaccharide), which has not been described to date, and does not contain phosphate substituents in the core region. Fatty acid analysis of lipid A identified (R)-3-hydroxytetradecanoic acid as sole amide-linked fatty acid and (R)-3-hydroxytetradecanoic acid, tetradecanoic acid, small amounts of 2-hydroxytetradecanoic acid, hexadecanoic acid, and traces of dodecanoic acid as ester-linked fatty acids, substituting the carbohydrate backbone D-GlcpN4Pbeta1-->6D-GlcpNalpha1P. The nonreducing GlcN carries four fatty acids, present as two 3-O-tetradecanoyltetradecanoic acid residues, one of which is amide-linked and the other ester-linked to O-3'. The reducing GlcN is substituted in a nature fraction of lipid A by two residues of (R)-3-hydroxytetradecanoic acid, one in amide and the other in ester linkage at O-3. Two minor fractions of lipid A were identified; in one, the amide-linked (R)-3-hydroxytetradecanoic acid at the reducing GlcN is esterified with hexadecanoic acid, resulting in 3-O-hexadecanoyltetradecanoic acid, and in the second, one of the 3-O-tetradecanoyltetradecanoic acid residues at the nonreducing GlcN is replaced by 3-O-dodecanoyltetradecanoic acid. Thus, the complete structure of LPS is as shown in Fig. 1. After immunization of BALB/c mice, two monoclonal antibodies were obtained that were shown to be specific for the core of LPS from K. pneumoniae ssp. pneumoniae, since they did not react with LPS or whole-cell lysates of a variety of other Gram-negative species. Both monoclonal antibodies could be inhibited by LPS but not by isolated oligosaccharides and are thus considered to recognize a conformational epitope in the core region.

Potential virulence factors of Proteus bacilli

The object of this review is the genus Proteus, which contains bacteria considered now to belong to the opportunistic pathogens. Widely distributed in nature (in soil, water, and sewage), Proteus species play a significant ecological role. When present in the niches of higher macroorganisms, these species are able to evoke pathological events in different regions of the human body. The invaders (Proteus mirabilis, P. vulgaris, and P. penneri) have numerous factors including fimbriae, flagella, outer membrane proteins, lipopolysaccharide, capsule antigen, urease, immunoglobulin A proteases, hemolysins, amino acid deaminases, and, finally, the most characteristic attribute of Proteus, swarming growth, enabling them to colonize and survive in higher organisms. All these features and factors are described and commented on in detail. The questions important for future investigation of these facultatively pathogenic microorganisms are also discussed.

Structure of the core oligosaccharide in the serotype O8 lipopolysaccharide from Klebsiella pneumoniae

Two classes of mutants with O-antigen-deficient lipopolysaccharides were isolated from the serotype O8 reference strain, belonging to Klebsiella pneumoniae subspecies ozaenae. These mutants were selected by resistance to bacteriophage KO1-2, which recognizes and lyses strains with lipopolysaccharide molecules containing the D-galactan II O antigen. Strain RFK-11 contains a defect in O-antigen synthesis and has a complete core, including the attachment site for O antigen. This mutation is complemented by a plasmid carrying the rfb (O-antigen biosynthesis) gene cluster from the related K. pneumoniae serotype O1. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the lipopolysaccharide from strain RFK-9 has a mobility typical of deep-rough lipopolysaccharide. RFK-9 lipopolysaccharide lacks the attachment site for O antigen. Lipopolysaccharides from strains RFK-9 and RFK-11 were isolated, and their structures were determined by methylation analyses, muclear magnetic resonance spectroscopy, and mass spectroscopy. The deduced O8 core oligosaccharide includes the partial core structure reported for the K. pneumoniae subspecies pneumoniae serotype O1 lipopolysaccharide (M. Süsskind, S. Müller-Leonnies, W. Nimmich, H. Brade, and O. Holst, Carbohydr. Res. 269:C1-7, 1995), consistent with the possibility of a conserved core structure within the species. The core oligosaccharide differs from those of the genera Salmonella and Escherichia by the absence of a hexose-containing outer core, the lack of phosphate residues in the inner core, and the presence of galacturonic acid residues.

The structure and serological specificity of Proteus mirabilis O43 O antigen

On the basis of sugar analysis and NMR spectroscopy, including selective spin-decoupling, one-dimensional NOE, two-dimensional homonuclear and 13C,1H-heteronuclear correlation spectroscopy, the following structure of the acidic O-specific polysaccharide of Proteus mirabilis O43 was established: -->4)-alpha-D-GalpA-(1-->3)-alpha-D-GalpA-(1-->3)-alpha-D-Gl cpNAc-(1-->4)-alpha - D-Glcp-(1-->, where GalA is galacturonic acid and Galp is galactopyranose. No serological cross-reactivity was observed between lipopolysaccharides of P. mirabilis O43 and other studied Proteus strains, except for P. mirabilis O10. The O-specific polysaccharide of P. mirabilis O43 was serologically active in precipitation and inhibition tests but the activity was lost after periodate oxidation. These data suggest that the O43 specificity is determined by a wide epitope with the immunodominant role of 4-substituted D-Glc or/and D-GalA, which are destroyed by periodate oxidation.

4-Amino-4-deoxy-L-arabinose in LPS of enterobacterial R-mutants and its possible role for their polymyxin reactivity

The content of 4-amino-4-deoxy-L-arabinopyranose (L-Arap4N) and the phosphate substitution pattern of the LPS of various strains from Salmonella minnesota, Yersinia enterocolitica and Proteus mirabilis was determined by GC/MS, HPLC and 31P-NMR. These data allowed us to examine the possible role of these components for the polymyxin B-binding capacity of LPS and for the minimal inhibiting concentration (MIC) and the minimal bactericidal concentration (MBC) of polymyxins B and E towards the respective R-mutants. Contrary to other investigated Re-, Rd- and Rc-mutants of S. minnesota, strain R595 (Re-mutant) showed about a 90% substitution of the ester-linked phosphate-group with L-Arap4N, whereas the L-Arap4N content of the other S. minnesota strains amounted to 17-25%. Neither the binding capacity of LPS to polymyxin B, determined by a bioassay, nor the MIC- and MBC-values of the R-mutants were significantly affected by this alteration. Similar results were obtained after using the temperature-dependent changes in the L-Arap4N-content and phosphate substitution pattern of Y. enterocolitica 75R. In order to explore the relevant polymyxin B binding site, lipid A samples with or without substitution of their ester-linked phosphate group were prepared and subjected to the polymyxin-binding assay. The results obtained so far indicated that the inner core bound L-Arap4N, detected in all resistant strains investigated, may play a decisive role in the decreased binding of polymyxin B, responsible for the bacterial resistance towards polymyxin(s).

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.

Structural differences in the outer core region of lipopolysaccharides derived from members of the genus Salmonella

Spontaneous and P22-resistant rough mutants, respectively, selected from Salmonella IV (18: z36, z38:-) and S. djakarta (48: z4, z24:-), appeared to lack the epitope recognized by the T6 monoclonal antibody which had been previously shown to correspond to the terminal alpha-1,2-linked N-acetyl-D-glucosamine residue of the Salmonella lipopolysaccharide (LPS) Ra core. LPSs and core oligosaccharides were therefore prepared from these two rough mutants and analysed by chemical and serological methods. Sugar analyses as well as methylation and 13C-NMR studies indicated that rough mutants derived from these two serotypes indeed possessed outer core structures differing from those of the well-characterized Salmonella Ra core. Serological data corroborated the chemical findings. Proposed structures of the outer core regions of these two R-types are presented and the significance of the findings is discussed.

Structural analysis of the heptose/hexose region of the lipopolysaccharide from Escherichia coli K-12 strain W3100

The disaccharide L-glycero-D-manno-heptosyl-D-glucose was isolated from the lipopolysaccharide (LPS) of Escherichia coli K-12 strain W3100 after partial hydrolysis with acid, and the structure was determined by methylation analysis, n.m.r. spectroscopy, and comparison with a synthetic standard. In addition, the oligosaccharides L,D-Hep-D-Glc-D-Glc and L,D-Hep-D-Glc-D-Glc-D-Glc were isolated, and their structures were established by g.l.c.-m.s. and methylation analysis. The results indicated that L-glycero-D-manno-heptose, a characteristic constituent of the inner core region, may also occur in the outer core region which, in E. coli, is generally composed of hexoses. A revised structure of the carbohydrate backbone of the hexose/heptose region of the LPS is given.

Smooth lipopolysaccharide of Salmonella adelaide has an atypical Salmonella Ra core

Two wild isolates as well as two laboratory strains of Salmonella adelaide obtained from different geographical areas failed to react with a monoclonal antibody directed against the terminal alpha-1,2-linked N-acetylglucosamine residue of the outer core of Salmonella lipopolysaccharide (LPS). This finding was confirmed by the lack of reactivities of Salmonella Ra LPS with S. adelaide antiserum or of S. adelaide R oligosaccharide with Salmonella Ra serum. Furthermore, S. adelaide proved to be resistant to lysis by phage FO1, which binds to a receptor also believed to involve the terminal alpha-1,2-linked N-acetylglucosamine of the Salmonella R oligosaccharide. These results suggest that the outer core structure of S. adelaide LPS may be different from that of S. typhimurium and other Salmonella strains.