The compositional analysis of bacterial extracellular polysaccharides by high-performance anion-exchange chromatography

Acid hydrolysis conditions for quantification of meningococcal X polysaccharide in a pentavalent vaccine using HPAEC-PAD/ESI-MS

A selective and sensitive method was evaluated for quantitation of meningococcal X (Men X) polysaccharide in pentavalent meningococcal A, C, W, Y and X conjugate vaccine using different acid hydrolysis conditions like HCl, TFA, HF, HF-TFA, and HF-HCl. High-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) using CarboPac PA10 column was used to identify the hydrolyzed products based on retention time and its comparison with monosaccharide standards. Complete release of glucosamine (GlcN) from Men X in monovalent bulk and pentavalent vaccine samples was achieved using HF hydrolysis at 80 °C for 2 h. The Men X HF-hydrolyzed polysaccharide to glucosamine along with the reference standard was identified using collision-induced dissociation (CID) electrospray mass spectroscopy and the MS/MS fragments of m/z 162, m/z 144 and m/z 84. Meningococcal polysaccharide concentration was determined with a correlation coefficient r2 >0.99 using polysaccharide reference standard. The serogroups A, W, and Y were converted to their monosaccharides units and quantified using this method however, milder acid hydrolysis 0.1 M HCl 80 °C 2 h for release of sialic acid for Men C polysaccharide was found to be more suitable. These methods will provide necessary tools and prove to be beneficial to laboratories developing new saccharide-based vaccine combinations.

Isolation of an Exopolysaccharide-producing Bacterium,Sphingomonassp. CS101, Which Forms an Unusual Type of Sphingan

An exopolysaccharide-producing Gram negative bacterium was isolated and determined to be a Sphingomonas sp. (CS101). A sugar composition analysis of an exopolysaccharide indicated that the Sphingomonas sp. CS101 secreted an exopolysaccharide composed of glucose, mannose, fucose, and rhamnose in the ratio of 2.1:1.1:1.0:0.1, suggesting that this exoplysaccharide is an unusual type of sphingan family. The mean molecular weight of the exopolysaccharide was determined to be 4.2x10(5) Da by size exclusion chromatography coupled with multi-angle laser-light scattering (SEC/MALLS) analysis. An exopolysaccharide was produced up to 17 g/l (pH 7; 30 degrees C) with the optimal medium condition over 4 days of cultivation.

Chemical Composition of Two Exopolysaccharides from Bacillus thermoantarcticus

The thermophilic bacterium Bacillus thermoantarcticus produces two exocellular polysaccharides (EPS 1 and EPS 2), which can be obtained from the supernatant of liquid cultures by cold-ethanol precipitation, in yields as high as 400 mg liter(sup-1). The EPS fraction was produced with all substrates tested, although a higher yield was obtained with mannose as the carbon and energy source. The EPS content was proportional to the total biomass. On a weight basis, EPS 1 and EPS 2 represented about 27 and 71%, respectively, of the total carbohydrate fraction. EPS 1 is a sulfate heteropolysaccharide containing mannose and glucose in a relative molar proportion of 1.0 and 0.7, respectively. EPS 2 is a sulfate homopolysaccharide containing mannose as the major component. The absolute configurations of hexoses were shown to be d for both EPSs. Nuclear magnetic resonance spectra confirmed the presence of (alpha)-d-mannose and (beta)-d-glucose in EPS 1 and only (alpha)-d-mannose in EPS 2. In addition, (sup1)H nuclear magnetic resonance analysis and chemical analysis indicated the presence of pyruvic acid in EPS 2.

Total compositional analysis by high-performance liquid chromatography or gas-liquid chromatography

Once the presence of carbohydrate in a glycoprotein has been confirmed, the next step is to determine the precise molar ratio of its monosaccharide constituents. The analysis involves two major phases. The release of the individual monosaccharides is achieved by methanolysis (described here), total acid hydrolysis, or enzymatic release of sialic acids. The resulting mixtures of monosaccharides are then analyzed by methods described in this unit: fractionation, characterization, and quantitation by high-performance liquid chromatography using anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and other HPLC systems or by gas-liquid chromatography with flame ionization detection. The identity of the individual monosaccharides is determined by comparison with known standards processed and analyzed in the same way.

Hydrolysis of grapefruit peel waste with cellulase and pectinase enzymes

Approximately 1 million metric tons of grapefruit were processed in the 2003/04 season resulting in 500,000 metric tons of peel waste. Grapefruit peel waste is usually dried, pelletized, and sold as a low-value cattle feed. This study tested different loadings of commercial cellulase and pectinase enzymes and pH levels to hydrolyze grapefruit peel waste to produce sugars. Pectinase and cellulase loadings of 0, 1, 2, 5, and 10mgprotein/g peel dry matter were tested at 45 degrees C. Hydrolyses were supplemented with 2.1mg beta-glucosidase protein/g peel dry matter. Five mg pectinase/g peel dry matter and 2mgcellulase/g peel dry matter were the lowest loadings to yield the most glucose. Optimum pH was 4.8. Cellulose, pectin, and hemicellulose in grapefruit peel waste can be hydrolyzed by pectinase and cellulase enzymes to monomer sugars, which can then be used by microorganisms to produce ethanol and other fermentation products.

Determination of sugar compounds in atmospheric aerosols by liquid chromatography combined with positive electrospray ionization mass spectrometry

We here report a method for the determination of sugar compounds of known presence in atmospheric aerosols using liquid chromatography (LC) combined with positive electrospray ionization mass spectrometry (MS). The target analytes include C(3)-C(6) monosaccharide alcohols (glycerol, erythritol, xylitol, mannitol), C(5)-C(6) monosaccharides (xylose, glucose, and levoglucosan), a disaccharide (sucrose), and a trisaccharide (melezitose). A mobile phase consisting of 20% 10 mM aqueous ammonium acetate, 8% methanol, and 72% water was found to provide abundant [M+NH(4)](+) adduct ions when coupled with electrospray ionization. Use of a polymer-based amino analytical column resolved the target compounds from the bulk solvent and provided limited separation among the target compounds. The target analytes were quantified using their [M+NH(4)](+) ions. Sample pretreatment was greatly simplified in comparison with the more commonly used gas chromatographic methods. It involved extraction of aerosol filters in methanol, evaporation of the solvent, and reconstitution with 5 mM ammonium acetate in water prior to the LC-MS analysis. The analyte recoveries were measured at the levels of 100, 500 and 1000 microg/L to be in the range of 78-102%, 94-112%, and 92-110%, respectively. The detection limits were lower than 10 pmol/injection for the tested target compounds except for xylose. Xylose had a detection limit of 95 pmol/injection. The method was applied to analyze 30 atmospheric aerosol samples to demonstrate its feasibility. The LC-MS method made possible the detection of trisaccharides as aerosol constituents for the first time.

Development of a high-performance anion-exchange chromatography with pulsed-amperometric detection based quantification assay for pneumococcal polysaccharides and conjugates

A method, using high-performance anion-exchange chromatography with pulsed-amperometric detection (HPAEC-PAD), has been developed to determine the concentrations of Streptococcus pneumoniae capsular polysaccharides and polysaccharide conjugates used in formulating a conjugate vaccine for the prevention of pneumococcal infections. In an effort to determine optimum hydrolysis conditions for the analysis, pneumococcal polysaccharides were subjected to three different hydrolysis methods: trifluoroacetic acid (TFA) hydrolysis, methanolysis followed by TFA hydrolysis, or hydrofluoric acid (HF) hydrolysis followed by TFA hydrolysis. For quantification purposes, best results were obtained by methanolysis followed by TFA hydrolysis for uronic acid-containing polysaccharides, and by TFA hydrolysis for all the others. For the quantification of all the polysaccharides (from native to conjugated forms), a monosaccharide reference mixture (Rha, Gal and GlcA) hydrolyzed along with the samples can be used as standards for routine analysis. This is much more convenient than to hydrolyze a well-characterized reference polysaccharide (necessary standard only for type 1 capsular polysaccharide). This method is rapid, very sensitive (less than 10 microg of polysaccharide is required), and may replace advantageously the currently used colorimetric assays used to determine polysaccharides content. Moreover, it can be readily adapted for use with other bacterial polysaccharide preparations as well.

Purification and characterization of a beta-glucosidase from Citrus sinensis var. Valencia fruit tissue

A preliminary survey demonstrated activity for alpha-D-glucosidase, alpha-D-mannosidase, alpha-L-arabinosidase, beta-D-glucosidase, beta-D-xylosidase, and beta-D-galactosidase in orange fruit flavedo and albedo tissue. alpha-L-Rhamnosidase was not detected. Subsequently, a beta-glucosidase was purified from mature fruit rag tissue (composed of intersegmental septa, squeezed juice sacs, and fruit core tissue) of Citrus sinensis var. Valencia. The beta-glucosidase exhibited low levels of activity against p-nitrophenyl-beta-D-fucopyranoside (13.5%) and p-nitrophenyl-alpha-D-glucopyranoside (7.0%), compared to its activity against p-nitrophenyl-beta-D-glucopyranoside (pNPG, 100%). The enzyme was purified by a combination of ion exchange (anion and cation) and gel filtration (Superdex and Toyopearl HW-55S) chromatography. It has an apparent molecular mass of 64 kDa by denaturing electrophoresis or 55 kDa by gel filtration chromatography (BioGel P-100). Hydrolysis of pNPG demonstrated a pH optimum between 4.5 and 5.5. At pH 5.0 the temperature optimum was 40 degrees C. At pH 5.0 and 40 degrees C the K(m) for pNPG was 0.1146 mM and it had a V(max) of 5.2792 nkatal x mg(-1) protein (katal = 0.06 International Units = the amount of enzyme that produces, under standard conditions, one micromol of product per min). Of the substrates tested, the enzyme was most active against the disaccharide cellobiose (1-->4), but was not active against p-nitrophenyl-beta-D-cellobioside. High levels of activity also were observed with the disaccharides laminaribiose (1-->3), gentiobiose (1-->6), and sophorose (1-->2). Activity greater than that observed with pNPG was obtained with the flavonoids hesperetin-7-glucoside and prunin (naringenin-7-glucoside), salicin, mandelonitrile-beta-D-glucoside (a cyanogenic substrate), and sinigrin (a glucosinolate). The enzyme was not active against amygdalin, coniferin, or limonin glucoside.

A thermophilic Bacillus isolated from an Eolian shallow hydrothermal vent, able to produce exopolysaccharides

A thermophilic aerobic microorganism, able to produce two exocellular polysaccharides (EPS1 and EPS2), was isolated from a shallow hydrothermal vent at Vulcano island (Eolian Islands, Italy). EPS1 and EPS2 were based on mannose and glucose although in a different ratio. EPS2 possessed a trisaccharide repeating unit with a manno-pyranoside configuration. New isolate phenotype was studied by physiological and morphological observations, including biochemical and antimicrobial susceptibility tests (134). Previous analyses carried out on 87 field isolates and 8 thermophilic reference bacilli displayed low phenotypic similarity level (S(SM) = 65%) with Bacillus thermodenitrificans DSM 465. Optimal growth occurs at 65 degrees C and pH 7.0. Oxidase and catalase are negative. The guanine-plus-cytosine (G+C) content of DNA is 52.7%. Genotypic investigations demonstrated the diversity of the isolate with fifteen selected thermophilic Bacillus spp. when we compared the restriction patterns of the amplified 16S rDNA. The membrane lipids are based on fatty acids mainly belonging to the iso-family.

Acid-catalyzed hydrolysis of hesperidin at elevated temperatures

Dilute sulfuric acid was used as a catalyst for hydrolysis of hesperidin suspensions in water at temperatures ranging from 25 to 180 degrees C. Significant acceleration of the reaction was observed at 120 degrees C and higher temperatures. This increase in the rate of hydrolysis can be attributed to increased solubilization of hesperidin in water at higher temperatures. Partial hydrolysis of hesperidin at 140 degrees C was used for the preparations of hesperetin-7-glucoside, which has a value in the synthesis of dihydrochalcone sweeteners. Simple separation of hesperetin and hesperetin-7-glucoside by extraction with dry acetone or lower alcohols has been developed.

Characterization of function and activity of domains A, B and C of xylanase C from Fibrobacter succinogenes S85

Xylanase C from the ruminant bacterium Fibrobacter succinogenes is comprised of two catalytic domains, A and B, and a third domain, C, of unknown function. The DNA coding for domains A and B of xylanase C were separately cloned and expressed in Escherichia coli as fusion proteins with glutathione-S:-transferase. The fusion proteins were isolated by affinity chromatography on glutathione-Sepharose 4B, cleaved with thrombin and the released xylanase C catalytic domains A and B were purified to apparent homogeneity by anion-exchange chromatography on Mono Q. Electrospray mass spectrometry provided a molecular mass of 27 818 Da (expected, 27 820 Da) for domain B. The pH and temperature optima for activity of domain B on oat spelt xylan were 5.0 and 52 degrees C, respectively. A kinetic analysis of the activity of the catalytic domain A on oat spelt xylan, birch wood xylan and xylooligomers at pH 6.5 and 37 degrees C provided data significantly different to those obtained previously with a protease-derived form of the enzyme [Zhu et al. (1994) J. Bacteriol. 176, 3885-3894]. The isolated domain A was more active on barley-glucan than the protease-derived form and its affinity for birch wood xylan was enhanced resulting in greater overall catalytic efficiency as reflected by k(cat)/K:(M) values. Likewise, significant differences in the Michaelis-Menten parameters K:(M), k(cat) and k(cat)/K:(M) were obtained with domain B compared with values previously reported with this domain attached to domain C. In general, the presence of domain C appeared to decrease the overall efficiency of domain B 7- and 36-fold with birch wood xylan and xylopentaose as substrates, respectively, as reflected by values of k(cat)/K:(M). The removal of domain C also affected the mode of action of domain B such that it more closely resembled that of catalytic domain A. However, no change in either pH and temperature optima or stability were found with domain B compared with the combined domains B and C. The function of domain C remains unknown, but hydrophobic cluster analysis indicated that it may belong to a class of dockerin domains involved in the protein-protein interactions of cellulolytic and xylanolytic complexes.

Monosaccharide composition of sweetpotato fiber and cell wall polysaccharides from sweetpotato, cassava, and potato analyzed by the high-performance anion exchange chromatography with pulsed amperometric detection method

The cell wall materials (CWMs) from sweetpotato (Ipomoea batatas cv. Kokei 14), cassava (Manihot esculenta), and potato (Solanum tuberosum cv. Danshaku) and commercial sweetpotato fiber as well as their polysaccharide fractions were analyzed for sugar composition by the high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) method. The separation of arabinose and rhamnose, and xylose and mannose, by this method has been improved using a CarboPac PA 10 column. Pretreatment of the CWMs and cellulose fractions with 12 M H(2)SO(4) was required for complete hydrolysis to occur. Commercial sweetpotato fiber was found to be mainly composed of glucose (88.4%), but small amounts of other sugars were also detected. Among the root crops, sweetpotato CWM had the highest amount of pectin and galacturonic acid. Fucose was detected only in cassava CWM and its hemicellulose fraction, while galactose was present in the highest amount in potato CWM. Among the polysaccharide fractions, it was only in the hemicellulose fraction where significant differences in the sugar composition, especially in the galactose content, were observed among the root crops.

Purification of citrus peel juice and molasses

Citrus peel juice and molasses are extremely bitter and unpalatable byproducts of orange and grapefruit juice production. Major components of interest are soluble sugars, glucose, fructose, and sucrose, which account for 60-70% of the dry solids. Analyses indicate that the remaining components are suspended tissue fragments, proteins, organic acids, mineral ions, phenolic compounds, and polyols. A purification sequence that removed a majority of bitter limonoids and phenolic compounds by adsorption on nonionic, macroporous resins was tested. Residual phenolic compounds were removed by adsorption on activated carbon or anion-exchange resin, which also removed anions of organic and inorganic acids. Taste panel results suggested that debittered products could be acceptable for food uses.

Carbohydrate profiling of bacteria by gas chromatography-mass spectrometry and their trace detection in complex matrices by gas chromatography-tandem mass spectrometry

Bacterial cellular polysaccharides are composed of a variety of sugar monomers. These sugars serve as chemical markers to identify specific species or genera or to determine their physiological status. Some of these markers can also be used for trace detection of bacteria or their constituents in complex clinical or environmental matrices. Analyses are performed, in our hands, employing hydrolysis followed by the alditol acetate derivatization procedure. Substantial improvements have been made to sample preparation including simplification and computer-controlled automation. For characterization of whole cell bacterial hydrolysates, sugars are analyzed by gas chromatography-mass spectrometry (GC-MS). Simple chromatograms are generated using selected ion monitoring (SIM). Using total ion GC-MS, sugars can be readily identified. In more complex clinical and environmental samples, markers for bacteria are present at sufficiently low concentrations that more advanced instrumentation, gas chromatography-tandem mass spectrometry (GC-MS-MS), is preferred for optimal analysis. Using multiple reaction monitoring, MS-MS is used (replacing more conventional SIM) to ignore extraneous chromatographic peaks. Triple quadrupole and ion trap GC-MS-MS instruments have both been used successfully. Absolute chemical identification of sugar markers at trace levels is achieved, using MS-MS, by the product spectrum.

A novel high-performance anion-exchange chromatographic method for the analysis of carrageenans and agars containing 3,6-anhydrogalactose

A novel method has been developed to determine the sugar composition of 3,6-anhydrogalactose-containing polysaccharides, such as carrageenan and agar. The method is based on reductive hydrolysis with a methylmorpholine-borane complex in the presence of acid and subsequent high-performance anion-exchange chromatography analysis of the alditols without any derivatization. The method was validated by 13C NMR analysis of six carrageenans and three agars and by a previously used method based on derivatization to alditol acetates and gas-liquid chromatography analysis. The new method was found to be superior to the gas-liquid chromatography method as the analysis time was less than half. Also it was found to be more accurate and reproducible and no derivatization was required. The analysis of the six different carrageenan samples revealed that homogeneous mu- and nu-carrageenan, theoretically without 3,6-anhydrogalactose residues, cannot be isolated from red seaweeds. Consequently, the question arose if mu- and nu-carrageenans at all are present in seaweeds and if the current hypotheses regarding biosynthesis of carrageenans in the seaweeds are correct. The data demonstrated that carrageenans are highly complex natural polysaccharides, which are more irregular than assumed hitherto. The new analytical technique will permit elucidation of the detailed structure of seaweed polysaccharides and determination of their structure-property relationships.

Assignment of biochemical functions to glycosyl transferase genes which are essential for biosynthesis of exopolysaccharides in Sphingomonas strain S88 and Rhizobium leguminosarum

Glycosyl transferases which recognize identical substrates (nucleotide-sugars and lipid-linked carbohydrates) can substitute for one another in bacterial polysaccharide biosynthesis, even if the enzymes originate in different genera of bacteria. This substitution can be used to identify the substrate specificities of uncharacterized transferase genes. The spsK gene of Sphingomonas strain S88 and the pssDE genes of Rhizobium leguminosarum were identified as encoding glucuronosyl-(B1-->4)-glucosyl transferases based on reciprocal genetic complementation of mutations in the spsK gene and the pssDE genes by segments of cloned DNA and by the SpsK-dependent incorporation of radioactive glucose (Glc) and glucuronic acid (GlcA) into lipid-linked disaccharides in EDTA-permeabilized cells. By contrast, glycosyl transferases which form alternative sugar linkages to the same substrate caused inhibition of polysaccharide synthesis or were deleterious or lethal in a foreign host. The negative effects also suggested specific substrate requirements: we propose that spsL codes for a glucosyl-(beta1-->4)-glucuronosyl transferase in Sphingomonas and that pssC codes for a glucuronosyl-(beta1-->4)-glucuronosyl transferase in R. leguminosarum. Finally, the complementation results indicate the order of attachment of sphingan main-chain sugars to the C55-isoprenylphosphate carrier as -Glc-GlcA-Glc-isoprenylpyrophosphate.

The cell wall polymer of the extremely halophilic archaeon Natronococcus occultus

The cell wall polymer of Natronococcus occultus (DSM 3396) consists of L-glutamate, N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, D-galacturonic acid, D-glucuronic acid and D-glucose in a molar ratio of 5:7:1:8:0.5:0.3. Partial acid hydrolysis of the cell wall polymer produced soluble fragments that could be separated by HPLC. A gamma-glutamyl dipeptide was isolated. In the intact cell wall polymer, the glutamate residues form a poly-(gamma-glutamine) chain with a length of about 60 monomers, which corresponds to a relative molecular mass of approximately 7700 Da. Two other soluble dimeric fragments, composed of glutamate and either glucosamine or galactosamine in a molar ratio of 1:1, were purified from the hydrolysate, suggesting the presence of two different oligosaccharides linked to the poly-(gamma-glutamine) chain of the intact polymer. The analysis of additional fragments, which were composed of an amino sugar and galacturonic acid or glucose indicated that one oligosaccharide consisted of a glucosamine pentamer in an alpha-1,3 linkage at the reducing end and an oligomer with at least five beta-1,4-linked galacturonic acid residues at the non-reducing end. The second oligosaccharide was comprised of a galactosamine dimer in a beta-1,3 linkage at the reducing end and a maltose unit at the non-reducing end. Both oligosaccharides were linked to the alpha-amide group of the glutamine residues of the poly-(gamma-glutamine) chain. The whole cell wall polymer, which represents a novel type of natural glycoconjugate, has a relative molecular mass of 54 kDa.

Bacterial genetic loci implicated in the Pseudomonas putida GR12-2R3--canola mutualism: identification of an exudate-inducible sugar transporter

Pseudomonas putida GR12-2R3 promotes the emergence and growth of diverse plant species. Analyses of TnphoA insertion mutations are revealing bacterial characteristics pertinent to the plant-microbe interaction. Pseudomonas putida PG269 is a TnphoA insertion derivative of GR12-2R3 that expresses canola seed exudate-inducible alkaline phosphatase (PhoA) activity. It promoted the growth of canola roots, as well as strain GR12-2R3, and outgrew its parent when they were cocultured in the presence of canola roots or in liquid seed exudate medium. (In contrast, mutant PG126 failed to promote canola root growth and was outgrown by its parent strain.) The PhoA activity of strain PG269 was induced by glucosamine and other sugars; glucosamine inhibited the growth of strain GR12-2R3 and stimulated the growth of strain PG269. Strain PG269 contained two TnphoA insertions: seiA1::TnphoA and seiB1::TnphoA. Strain PG312, which contained only insertion seiA1::TnphoA, shared all aspects of the PG269 phenotype, except the ability to outcompete strain GR12-2R3 during coculture. Insertion seiA1::TnphoA interrupted an open reading frame related in sequence to members of the MalF family of sugar transporter subunits. The PhoA-inducing fraction of canola seed exudate was hydrophilic, low in molecular weight, and heat stable. It cochromatographed with basic amino acids and amino sugars, and was inactivated by strains GR12-2R3 and PG269. Gene seiA may encode a subunit of an ABC transporter with broad specificity for glucose and related sugars whose expression can be induced by exudate sugars.

Quantitative analysis of neutral and acidic sugars in whole bacterial cell hydrolysates using high-performance anion-exchange liquid chromatography-electrospray ionization tandem mass spectrometry

A procedure for analysis of a mixture of neutral and acidic sugars in bacterial whole cell hydrolysates using high-performance anion-exchange liquid chromatography-electrospray ionization tandem mass spectrometry (HPAEC-ESI-MS-MS) is described. Certain bacteria (including bacilli), grown under phosphate-limited conditions, switch from producing a teichoic acid (containing ribitol) to a teichuronic acid (characterized by glucuronic acid content). Bacterial cells were hydrolyzed with sulfuric acid to release sugar monomers. The solution was neutralized by extraction with an organic base. Hydrophobic and cationic contaminants (including amino acids) were removed using C18 and SCX columns, respectively. HPAEC is well established as a high-resolution chromatographic technique, in conjunction with a pulsed amperometric detector. Alternatively, for more selective detection, sugars (as M-H- ions) were monitored using ESI-MS. In HPAEC, the mobile phase contains sodium hydroxide and sodium acetate, which are necessary for chromatographic separation of mixtures of neutral and acidic sugars. Elimination of this high ionic content prior to entry into the ESI ion source is vital to avoid compromising sensitivity. This was accomplished using an on-line suppressor and decreasing post-column flow-rates from 1 ml to 50 microliters/min. In the selected ion monitoring mode, background (from the complex sample matrix as well as the mobile phase) was eliminated, simplifying chromatograms. Sugar identification was achieved by MS-MS using collision-induced dissociation.

Biochemical changes in the equine capsule following prostaglandin-induced pregnancy failure

The equine embryonic capsule, an acellular covering that envelops the conceptus during the second and third weeks of pregnancy, is composed of mucin-like glycoproteins. Its structure is consistent with a dual role during early pregnancy: protection of the conceptus, and communication between the embryo and the mother. Loss of sialic acid from the capsular glycoproteins at day 16 correlates with the time of "fixation," or loss of conceptus mobility throughout the uterine horns. This study investigated how the structure of the capsule is linked to the maintenance of pregnancy. Six pregnancies, confirmed by ultrasound, were terminated by prostaglandin injection on day 14, prior to the time of embryo fixation. These "defective" conceptuses were collected at day 17, and the structure and molecular properties of their capsules were compared to those of day 17 conceptuses collected from 5 normal pregnancies. Defective capsules were not significantly different from normal capsules in terms of dry weight, amino acid composition, and content of neutral and amino sugars. However, defective capsules failed to show the loss of sialic acid normally occurring around the time of embryo fixation. Analysis of the capsular mucins following trypsin digestion was carried out by radioactive labeling with 3H on sialyl-oligosaccharides and 125I on tyrosine residues, followed by fast protein liquid chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Differences in the trypsin fragmentation patterns indicated increased susceptibility of the defective capsules to proteolysis. We conclude that there is a temporal association between desialylation of the equine capsule and embryonic survival, and that failure to desialylate alters the properties of the capsule.

A novel pathway for O-polysaccharide biosynthesis in Salmonella enterica serovar Borreze

The plasmid-encoded gene cluster for O:54 O-polysaccharide synthesis in Salmonella enterica serovar Borreze (rfbO:54) contains three genes that direct synthesis of a ManNAc homopolymer with alternating beta1,3 and beta1,4 linkages. In Escherichia coli K-12, RfbAO:54 adds the first ManNAc residue to the Rfe (UDP-GlcpNAc::undecaprenylphosphate GlcpNAc-1-phosphate transferase)- modified lipopolysaccharide core. Hydrophobic cluster analysis of RfbAO:54 indicates this protein belongs to the ExoU family of nonprocessive beta-glycosyltransferases. Two putative catalytic residues and a potential substrate-binding motif were identified in RfbAO:54. Topological analysis of RfbBO:54 predicts four transmembrane domains and a large central cytoplasmic domain. The latter shares homology with a similar domain in the processive beta-glycosyltransferases Cps3S of Streptococcus pneumoniae and HasA of Streptococcus pyogenes. Hydrophobic cluster analysis of RfbBO:54 and Cps3S indicates both possess the structural features characteristic of the HasA family of processive beta-glycosyltransferases. Four potential catalytic residues and a putative substrate-binding motif were identified in RfbBO:54. In Deltarfb E. coli K-12, RfbAO:54 and RfbBO:54 direct synthesis of smooth O:54 lipopolysaccharide, indicating that this O-polysaccharide involves a novel pathway for O-antigen transport. Based on sequence and structural conservation, 15 new ExoU-related and 17 new HasA-related transferases were identified.

Distribution of the rol gene encoding the regulator of lipopolysaccharide O-chain length in Escherichia coli and its influence on the expression of group I capsular K antigens

The rol (cld) gene encodes a protein involved in the expression of lipopolysaccharides in some members of the family Enterobacteriaceae. Rol interacts with one or more components of Rfc-dependent O-antigen biosynthetic complexes to regulate the chain length of lipopolysaccharide O antigens. The Rfc-Rol-dependent pathway for O-antigen synthesis is found in strains with heteropolysaccharide O antigens, and, consistent with this association, rol-homologous sequences were detected in chromosomal DNAs from 17 different serotypes with heteropolysaccharide O antigens. Homopolymer O antigens are synthesized by a pathway that does not involve either Rfc or Rol. It was therefore unexpected when a survey of Escherichia coli strains possessing mannose homopolymer O8 and O9 antigens showed that some strains contained rol. All 11 rol-positive strains coexpressed a group IB capsular K antigen with the O8 or O9 antigen. In contrast, 12 rol-negative strains all produced group IA K antigens in addition to the homopolymer O antigen. Previous research from this and other laboratories has shown that portions of the group I K antigens are attached to lipopolysaccharide lipid A-core, in a form that we have designated K(LPS). By constructing a hybrid strain with a deep rough rfa defect, it was shown that the K40 (group IB) K(LPS) antigen exists primarily as long chains. However, a significant amount of K40 antigen was surface expressed in a lipid A-core-independent pathway. The typical chain length distribution of the K40 antigen was altered by introduction of multicopy rol, suggesting that the K40 group IB K antigen is equivalent to a Rol-dependent O antigen. The prototype K30 (group IA) K antigen is expressed as short oligosaccharides (primarily single repeat units) in K(LPS), as well as a high-molecular-weight lipid A-core-independent form. Introduction of multicopy rol into the K30 strain generated a novel modal pattern of K(LPS) with longer polysaccharide chains. Collectively, these results suggested that group IA K(LPS) is also synthesized by a Rol-dependent pathway and that the typically short oligosaccharide K(LPS) results from the absence of Rol activity in these strains.

Novel, specific O-glycosylation of secreted Flavobacterium meningosepticum proteins. Asp-Ser and Asp-Thr-Thr consensus sites

A new type of O-linked oligosaccharide has been discovered on several proteins secreted by the Gram-negative bacterium Flavobacterium meningosepticum, including Endo F2 (three sites), Endo F3 (one site), and a P40 protease (one site). The oligosaccharide moiety is covalently attached via a mannose residue to a serine or threonine at consensus sites corresponding to Asp-Ser* or Asp-Thr*-Thr. Preliminary characterization by mass spectroscopy revealed an oligosaccharide of 1244 Da at each of the proposed glycosylation sites. Collision-associated dissociation analysis showed a characteristic daughter ion series of m/z 218, 394, and 556, indicative of a common Flavobacterium oligosaccharide. Compositional analysis demonstrated an unusual profile of monosaccharides, including hexoses, methylated hexoses, and uronic acid derivatives.

Isolation and partial characterization of rainbow trout (Oncorhynchus mykiss) gill mucin

Gill mucin from rainbow trout was isolated utilizing two rounds of cesium chloride density ultracentrifugation followed by gel filtration on Sepharose CL-2B. Neither density ultracentrifugation nor gel filtration alone was sufficient for purification of the mucin. Isolated gill mucin had a density of 1.5 g/ml and eluted at the void volume of the Sepharose CL-2B column. Silver-stained reducing 6% polyacrylamide gel electrophoresis of gill mucin produced a band at the origin with a smear entering the separating gel. There was no evidence of a link protein in gill mucin on reducing 12% polyacrylamide gel electrophoresis. Gill mucin had an amino acid profile similar to that of mucins in other species. Specifically, 35.1% of the total amino acids were represented by threonine and serine, while another 27.5% were alanine and proline. Gill mucin contained galactose (26.7 ± 3.2%), galactosamine (22.5 ± 4.4%), glucose (16.6 ± 8.7%), fucose (16.1 ± 1.5%), glucosamine (12.0 ± 1.9%) and mannose (5.1 ± 4.4%). Uronic acid levels from purified mucin were very low (0.7 ± 0.1%). Sialic acid was also present (0.06 g/g of mucin protein). The periodic acid-Schiff assay routinely utilized for detection of mucins was relatively insensitive for detection of gill mucin (6 × less sensitive than for pig gastric mucin) so a rabbit antiserum was raised. The antiserum produced profiles similar to the periodic acid-Schiff assay of fractions following gel filtration. Immunofluorescence of formalin-fixed rainbow trout gill tissue sections showed that the antiserum detected mucin within branchial goblet cells.

Formation of the K30 (group I) capsule in Escherichia coli O9:K30 does not require attachment to lipopolysaccharide lipid A-core

Escherichia coli K antigens (capsular polysaccharides) are divided into two broad classes, designated groups I and II, on the basis of a number of chemical, physical, and genetic criteria. Group I K antigens can be further subdivided on the basis of the absence (group IA) or presence (group IB) of amino sugars in the repeating unit of the K antigen. One criterion proposed for inclusion in group I is covalent linkage of the capsular polysaccharide to the lipid A-core of lipopolysaccharide (LPS). E. coli O9:K30 is a strain with a representative group IA K antigen. This organism synthesizes an LPS-associated low-molecular-weight form of K30 antigen which is called K(LPS). To determine the involvement of LPS lipid A-core in expression of the K30 capsular polysaccharide, E. coli K30/K-12 hybrid strains were constructed with mutations in the E. coli K-12 rfa locus, responsible for the biosynthesis of the LPS core oligosaccharide. These strains lack K(LPS), indicating that a full-length core is required for K(LPS) expression. However, formation of a K30 capsule was unaffected by rfa defects, indicating that attachment to lipid A-core is not an obligatory step for either export of high-molecular-weight capsular polysaccharide or maintenance of the capsular structure on the cell surface. Silver-stained tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles of lipopolysaccharides from other E. coli K serotypes showed that all strains with group IB K antigens expressed some K(LPS). In contrast, some strains with group IA K antigens appear to lack K(LPS). Consequently, although association of group 1 K antigens with lipid A-core is common, it is not a universal marker for inclusion in group I.

Separation of outer and cytoplasmic membranes of Fibrobacter succinogenes and membrane and glycogen granule locations of glycanases and cellobiase

The outer membrane (OM) of Fibrobacter succinogenes was isolated by a combination of salt, sucrose, and water washes from whole cells grown on either glucose or cellulose. The cytoplasmic membrane (CM) was isolated from OM-depleted cells after disruption with a French press. The OM and membrane vesicles isolated from the extracellular culture fluid of cellulose-grown cells had a higher density, much lower succinate dehydrogenase activity, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis protein profiles different from those of the CM. The OM from both glucose- and cellulose-grown cells and the extracellular membrane vesicles from cellulose-grown cultures exhibited higher endoglucanase, xylanase, and acetylesterase activities than the CM and other cell fractions. Endoglucanase 2 was absent from the isolated OM fractions of glucose- and cellulose-grown cells and from the extracellular membrane vesicles of cellulose-grown cells but was present in the CM and intracellular glycogen granule fractions, while endoglucanase 3 was enriched in the OM. Cellobiosidase was located primarily in the periplasm as previously reported, while cellobiase was mainly present in the glycogen granule fraction of glucose-grown cells and in a nongranular glycogen and CM complex in cellulose-grown cells. The cellobiase was not eluted from glycogen granules by cellobiose, maltose, and maltotriose nor from either the granules or the cell membranes by nondenaturing detergents but was eluted from both glycogen granules and cell membranes by high concentrations of salts. The eluted cellobiase rebound almost quantitatively when diluted and mixed with purified glycogen granules but exhibited a low affinity for Avicel cellulose. Thus, we have documented a method for isolation of OM from F. succinogenes, identified the OM origin of the extracellular membrane vesicles, and located glycanases and cellobiase in membrane and glycogen fractions.

Coexpression of colanic acid and serotype-specific capsular polysaccharides in Escherichia coli strains with group II K antigens

In Escherichia coli K-12, the rcsA and rcsB gene products are positive regulators in expression of the slime polysaccharide colanic acid. We have previously demonstrated the presence of rcsA sequences in E. coli K1 and K5, strains with group II capsular K antigens, and shown that introduction of multicopy rcsA into these strains results in the expression of colanic acid. We report here the presence of rcsB sequences in E. coli K1 and K5 and demonstrate that RcsB also plays a role in the biosynthesis of colanic acid in strains with group II K antigens. In E. coli K1 and K5 grown at 37 degrees C, multicopy rcsB and the resulting induction of colanic acid synthesis had no significant effect on synthesis of the group II K antigens. K-antigen-specific sugar transferase activities were not significantly different in the presence or absence of multicopy rcsB, and introduction of a cps mutation to eliminate colanic acid biosynthesis in a K1-derivative strain did not influence the activity of the polysialyltransferase enzyme responsible for synthesis of the K1 polymer. Furthermore, immunoelectron microscopy showed no detectable difference in the size or distribution of the group II K-antigen capsular layer in cells which produced colanic acid. Colanic acid expression therefore does not appear to significantly affect synthesis of the group II K-antigen capsule and, unlike for group I K antigens, expression of group II K antigens is not positively regulated by the rcs system.

Characterization of rcsB and rcsC from Escherichia coli O9:K30:H12 and examination of the role of the rcs regulatory system in expression of group I capsular polysaccharides

In Escherichia coli K-12, RcsC and RcsB are thought to act as the sensor and effector components, respectively, of a two-component regulatory system which regulates expression of the slime polysaccharide colanic acid (V. Stout and S. Gottesman, J. Bacteriol. 172:659-669, 1990). Here, we report the cloning and DNA sequence of a 4.3-kb region containing rcsC and rcsB from E. coli O9:K30:H12. This strain does not produce colanic acid but does synthesize a K30 (group I) capsular polysaccharide. The rcsB gene from E. coli K30 (rcsBK30) is identical to the rcsB gene from E. coli K-12 (rcsBK-12). rcsCK30 has 16 nucleotide changes, resulting in six amino acid changes in the predicted protein. To examine the function of the rcs regulatory system in expression of the K30 capsular polysaccharide, chromosomal insertion mutations were constructed in E. coli O9:K30:H12 to independently inactivate rcsBK30 and the auxiliary positive regulator rcsAK30. Strains with these mutations maintained wild-type levels of K30 capsular polysaccharide expression and still produced a K30 capsule, indicating that the rcs system is not essential for expression of low levels of the group I capsular polysaccharide in lon+ E. coli K30. However, K30 synthesis is increased by introduction of a multicopy plasmid carrying rcsBK30. K30 polysaccharide expression is also markedly elevated in an rcsBK30-dependent fashion by a mutation in rcsCK30, suggesting that the rcs system is involved in high levels of synthesis. To determine whether the involvement of the rcs system in E. coli K30 expression is typical of group I (K antigen) capsules, multicopy rcsBK30 was introduced into 22 additional strains with structurally different group I capsules. All showed an increase in mucoid phenotype, and the polysaccharides produced in the presence and absence of multicopy rcsBK30 were examined. It is has been suggested that E. coli strains with group I capsules can be subdivided based on K antigen structure. For the first time, we show that strains with group I capsules can also be subdivided by the ability to produce colanic acid. Group IA contains capsular polysaccharides (including K30) with repeating-unit structures lacking amino sugars, and expression of group IA capsular polysaccharides is increased by multicopy rcsBK30. Group IB capsular polysaccharides all contain amino sugars. In group IB strains, multicopy rcsBK30 activates synthesis of colanic acid.

Mucin-like glycoproteins in the equine embryonic capsule

The equine embryonic capsule replaces the zona pellucida and envelopes the conceptus during the second and third weeks of pregnancy. Although this capsule was described more than 100 years ago, its molecular structure has not been characterized. Here we present evidence that the glycoprotein(s) of the equine capsule resembles those of the mucin glycoprotein family. The resistance of the capsule to chemical and enzymatic solubilization was confirmed, and, as in mucins, protein constituted only 35-40% of its total dry mass. Determination of the sugar composition of the capsule using colorimetric assays and high-performance anion-exchange chromatography also showed it to have mucin-like characteristics. Gal, GalNAc, sulfated sugars, and sialic acid make up a high proportion of the capsular carbohydrate, while GlcNAc, Glc, and Man are minor components. These findings were verified using lectin histochemical staining of frozen sections of conceptuses. The results of amino acid analysis were also consistent with the proposal that the capsular glycoproteins belong to the mucin family. Removal of the covalently bound carbohydrate by beta-elimination under reducing conditions demonstrated that the capsule is O-glycosylated mainly on threonine residues. Affinity chromatography on jacalin-agarose confirmed that, like mucins, the capsular glycoproteins are heavily O-glycosylated. SDS-PAGE analysis revealed a prominent 21-kDa band, specific to the capsule, in preparations solubilized by trypsin but not by other proteases. Characterization of its constituent glycoprotein(s) should be helpful in elucidating the role of the capsule (and analogous blastocyst coverings in other species) during early pregnancy.

Carbohydrate analysis of water-soluble uronic acid-containing polysaccharides with high-performance anion-exchange chromatography using methanolysis combined with TFA hydrolysis is superior to four other methods

Sulfuric acid hydrolysis according to the Saeman procedure, TFA hydrolysis, and methanolysis combined with TFA hydrolysis were compared for the hydrolysis of water-soluble uronic acid-containing polysaccharides originating from fungi, plants, and animals. The constituent sugar residues released were subsequently analyzed by either conventional GLC analysis of alditol acetates or high-performance anion-exchange chromatography with pulsed-amperometric detection. It was shown that TFA hydrolysis alone is not sufficient for complete hydrolysis. Sulfuric acid hydrolysis of these polysaccharides resulted in low recoveries of 6-deoxy-sugar residues. Best results were obtained by methanolysis combined with TFA hydrolysis. Methanolysis with 2 M HCl prior to TFA hydrolysis resulted in complete liberation of monosaccharides from pectic material and from most fungal and animal polysaccharides tested. Any incomplete hydrolysis could be assessed easily by HPAEC, by the detection of characteristic oligomeric products, which is difficult using alternative methods currently in use. Methanolysis followed by TFA hydrolysis of 20 micrograms water-soluble uronic acid containing polysaccharides and subsequent analysis of the liberated sugar residues by HPAEC allowed us to determine the carbohydrate composition of these polysaccharides rapidly and accurately in one assay without the need for derivatization.