Structural characterization of an acidic exoheteropolysaccharide produced by the nitrogen-fixing bacterium Burkholderia tropica

An acidic exopolysaccharide (EPS) produced by the diazotrophic bacterium Burkholderia tropica, strain Ppe8, was isolated from the culture supernatant of bacteria grown in a synthetic liquid medium containing mannitol and glutamate. Monosaccharide composition showed Rha, Glc and GlcA in a 2.0:2.0:1.0 molar ratio, respectively. Further structural characterization was performed by a combination of NMR, mass spectrometry and chemical methods. Partial acid hydrolysis of EPS provided a mixture of acidic oligosaccharides that were characterized by ESI-MS, giving rise to ions with m/z 193 (GlcA-H)⁻, 339 (GlcA,Rha-H)⁻, 501 (GlcA,Rha,Glc-H)⁻, 647 (GlcA,Rha₂,Glc,-H)⁻, 809 (GlcA,Rha₂,Glc₂,-H)⁻ and 851 (GlcA,Rha₂,Glc₂,OAc-H)⁻. Carboxyreduced EPS (EPS-CR) had Glc and Rha in a 3:2 ratio, present as d- and l-enantiomers, respectively. Methylation and NMR analysis of EPS and EPS-CR showed a main chain containing 2,4-di-O-Rhap, 3-O-Rhap and 4-O-Glcp. A GlcA side chain unit was found in the acidic EPS, substituting O-4 of α-l-Rhap units. This was observed as a non-reducing end unit of glucopyranose in the EPS-CR. Acetyl esters occured at O-2 of β-l-Rhap units. From the combined results herein, we determined the structure of the exocellular polysaccharide produced by B. tropica, Ppe8, as being a pentasaccharide repeating unit as shown:

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Antitumor and immunomodulating activity of polysaccharides from Enteromorpha intestinalis

Two polysaccharides (WEA and WEB) were isolated from Enteromorpha intestinalis by hot water extraction, anion-exchange, and gel-permeation chromatography. The average molecular weights (Mw) of the two fractions were 72.03 kDa (WEA) and 60.12 kDa (WEB). WEA was composed of Rha, Xyl, Man, and Glc in a molar ratio of 1.39:1.00:0.13:3.23. WEB consisted of Rha, Xyl, Gal, and GlcA (glucuronic acid) in a molar ratio of 7.32:1.00:0.51:1.28. Both polysaccharides could inhibit tumor growth in S180 tumor-bearing mice, and increased the relative spleen and thymus weight. They also increased the expression of tumor necrosis factor-alpha (TNF-α) in serum. WEA and WEB induced lymphocyte proliferation, increased the production of TNF-α in macrophages, and stimulated macrophages to produce nitric oxide dose-dependently through the up-regulation of inducible NO synthase activity. However, no direct cytotoxicity against Sarcoma 180 was investigated in vitro. These results indicate that the antitumor effects of these polysaccharides are associated with immunostimulation.     

刺五加果水溶性多糖的研究——AS-2的分离纯化与结构探讨

从刺五加果中抽提出水溶性粗多糖。经酸性乙醇分级及反复冻融得到多糖AS-2。AS-2经Sepharose CL-4B柱层析为单一对称峰,经醋酸纤维素膜电泳为一条带,冻融后高速离心无沉淀可证明其为均一级分。G.C分析表明,AS-2由Ara、Xyl、Rha、Gal、Glc组成,其单糖摩尔比为1.6:1.2:1.8:1.0:3.6。AS-2的分子量约为78kD,比旋光度[α]_D~(25)=+17°,特性粘度[η]=0.068。红外光谱分析含β型糖苷键。部分酸水解、酶解、高碘酸酸化、Smith降解、完全甲基化、G.C,G.C-M.S的分析结果表明,以β(1→3)Glc及β(1→4)Glc构成分子的主链。Glc的C_3上带有分支,约每4个己糖残基带有1个侧链。侧链上,Rha多以1→4苷键相连,部分残基C_2上有分支。Gal存在(1→6)及(1→3)连接方式,多数Glc以(1→6)苷键连结,少数Glc出现在分子非还原末端。位于分子末端的还有Ara与Xyl。     

Exo-oligosaccharides of Rhizobium sp. strain NGR234 are required for symbiosis with various legumes

Rhizobia are nitrogen-fixing bacteria that establish endosymbiotic associations with legumes. Nodule formation depends on various bacterial carbohydrates, including lipopolysaccharides, K-antigens, and exopolysaccharides (EPS). An acidic EPS from Rhizobium sp. strain NGR234 consists of glucosyl (Glc), galactosyl (Gal), glucuronosyl (GlcA), and 4,6-pyruvylated galactosyl (PvGal) residues with beta-1,3, beta-1,4, beta-1,6, alpha-1,3, and alpha-1,4 glycoside linkages. Here we examined the role of NGR234 genes in the synthesis of EPS. Deletions within the exoF, exoL, exoP, exoQ, and exoY genes suppressed accumulation of EPS in bacterial supernatants, a finding that was confirmed by chemical analyses. The data suggest that the repeating subunits of EPS are assembled by an ExoQ/ExoP/ExoF-dependent mechanism, which is related to the Wzy polymerization system of group 1 capsular polysaccharides in Escherichia coli. Mutation of exoK (NGROmegaexoK), which encodes a putative glycanase, resulted in the absence of low-molecular-weight forms of EPS. Analysis of the extracellular carbohydrates revealed that NGROmegaexoK is unable to accumulate exo-oligosaccharides (EOSs), which are O-acetylated nonasaccharide subunits of EPS having the formula Gal(Glc)5(GlcA)2PvGal. When used as inoculants, both the exo-deficient mutants and NGROmegaexoK were unable to form nitrogen-fixing nodules on some hosts (e.g., Albizia lebbeck and Leucaena leucocephala), but they were able to form nitrogen-fixing nodules on other hosts (e.g., Vigna unguiculata). EOSs of the parent strain were biologically active at very low levels (yield in culture supernatants, approximately 50 microg per liter). Thus, NGR234 produces symbiotically active EOSs by enzymatic degradation of EPS, using the extracellular endo-beta-1,4-glycanase encoded by exoK (glycoside hydrolase family 16). We propose that the derived EOSs (and not EPS) are bacterial components that play a crucial role in nodule formation in various legumes.     

Human low-molecular-mass kininogen. Amino-acid sequence of the light chain; homology with other protein sequences

The chemical structure of the polysaccharide moiety of the lipopolysaccharide Rhodopseudomonas sphaeroides ATCC 17023 was established. Mild acetic acid hydrolysis of isolated lipopolysaccharide, followed by preparative high-voltage paper electrophoresis afforded three oligosaccharides. They were characterized by chemical and physicochemical studies to be: GlcA(alpha 1----4)dOclA8P, Thr(6') GlcA(alpha 1----4)GlcA and GlcA(alpha 1----4)dOclA, where GlcA is D-glucuronic acid and dOc1A is 3-deoxy-D-manno-octulosonic acid. Carboxyl-reduction of the lipopolysaccharide followed by acid hydrolysis gave a trisaccharide: GlcA(alpha 1----4)Glc(alpha 1----4)Glc, showing the presence of three residues of glucuronic acids in the O-specific chain and indicating that only two of them are reducible by NaBH4. The linkage between the polysaccharide and lipid A was shown to be through a single 1,4-linked residue of dOc1A attached by a 2,6'-linkage to the lipid A moiety.     

Structural analysis of gellans produced by Sphingomonas elodea strains by electrospray tandem mass spectrometry

A commercial gellan sample (Gelrite) and a gellan-like polymer (JB3) obtained by exposure of the producing strain to chemical mutagenesis were subjected to partial acid hydrolysis and the resultant oligosaccharides were identified by Electrospray Mass Spectrometry (ESI-MS) and Tandem Mass Spectrometry (ESI-MS/MS and MSⁿ). In both gellans, the main fragments were in accordance with the tetrasaccharide repeating unit, d-Glucose (Glc)-d-Glucuronic acid (GlcA)-d-Glucose (Glc)-l-Rhamose (Rha), described for the wild-type gellan, showing the higher acid lability of the Rha-(1 → 3)-Glc linkage when compared to the (1 → 4) of the other residues. Under the experimental conditions used in the study, as expected, no acyl substituents were observed in the commercial gellan but in JB3 oligosaccharides a glyceryl moiety was identified, substituted in the 3-linked Glc residue. Furthermore, the analysis of the MS/MS and MSⁿ spectra of both gellans allowed the identification of structural details, some of them not yet reported for these exopolysaccharides. The presence of oligosaccharides with single Glc and Rha residues substituent of the tetrasaccharide unit of gellan may represent novel side chains of the backbone unit that to our knowledge have never been reported previously for the gellan exopolysaccharide.     

Structural characterization of a highly branched polysaccharide from the seeds of Plantago asiatica L.

In this paper, polysaccharides were extracted from the seeds of Plantago asiatica L. with hot water and separated into three fractions PLP-1 (18.9%), PLP-2 (52.6%) and PLP-3 (28.5%) by Sephacryl™ S-400 HR column chomatography. The main fraction PLP-2's structure was elucidated using oxalic acid hydrolysis, partial acid hydrolysis, methylation, GC, GC-MS, 1D and 2D NMR. PLP-2 was composed of Rha, Ara, Xyl, Man, Glc and Gal, in a molar ratio of 0.05:1.00:1.90:0.05:0.06:0.10. Its uronic acid was GlcA. PLP-2 was highly branched heteroxylan which consisted of a β-1,4-linked Xylp backbone with side chains attached to O-2 or O-3. The side chains consisted of β-T-linked Xylp, α-T-linked Araf, α-T-linked GlcAp, β-Xylp-(1 → 3)-α-Araf and α-Araf-(1 → 3)-β-Xylp, etc. Based on these results, the structure of PLP-2 was proposed.     

Polysaccharides in desert reclamation: Compositions of exocellular proteoglycan complexes produced by filamentous blue-green and unicellular green edaphic algae

The filamentous blue-green alga Nostoc calcicola Geitler, strain 79WA01, showed a peak production of 70% of its biomass as a mixture of exocellular proteoglycan complexes, containing 3–30% of a polypeptide moiety and>70% of a complex glycuronoglycan. The former contained high proportions of Asp, Glu, Arg, and amido-NH₃, in addition to 35% of “hydrophobic” amino-acids. The latter varied in composition in different fractions: GalA (2.5–10.3%), GlcA (4.7–11.5%), Glc (11.7–39.0%), Xyl (5.7–17.9%), Man (2.7–9.5%), Gal (5.7–9.5%), Fuc (1.5–11.1%), Ara (1.9–4.3%), and Rha (1.4–4.4%). None of the fractions showed a stoichiometric ratio of sugar residues.

Palmelloid cells of three unicellular green soil-algae of the genus Chlamydomonas yielded 70% of their dry weight as capsular mucilage. About 50% of the sodium salt of this material was soluble in water, and contained 3–12% of polypeptide and 88–97% of glycuronoglycan (GlcA:Glc:Xyl = 1:1:3 for C. humicola Lucksch, and GlcA:Gal = 1:2 for C. peterfii Gerloff and C. sajao Lewin). These categorical differences in sugar composition, together with narrow composition distributions, suggested regular structures for the glycuronoglycans. The remainder of the mucilages contained essentially the same glycuronoglycan chains, but a higher proportion of polypeptide. These materials did not form true solutions in water, but dispersed as microgel particles.     

Production of exopolysaccharides from a thermophilic microorganism isolated from a marine hot spring in flegrean areas

A thermophilic strain isolated from sea sand at Maronti, near Sant' Angelo (Ischia), is described. The organism grows well at an optimal temperature of 60 °C at pH 7.0. The thermophilic bacterium, named strain 4004, produces an exocellular polysaccharide (EPS) in yields of 90 mg/l. The EPS fraction was produced with all substrates tested, although a higher yield was obtained with sucrose or trehalose as sole carbon source. During growth, the EPS content was proportional to the biomass. Three fractions (EPS1, EPS2, EPS3) were obtained after purification. Quantitative monosaccharide analysis of the EPSs revealed the presence of mannose:glucose:galactose in a relative ratio of 0.5:1.0:0.3 in EPS1, mannose:glucose:galactose in a relative ratio of 1.0:0.3:trace in EPS2, and galactose:mannose:glucosamine:arabinose in a relative ratio of 1.0:0.8:0.4:0.2 in EPS3. The average molecular mass of EPS3 was determined to be 1×10⁶ Da. From comparison of the chemical shift values in ¹H and ¹³C spectra, we conclude that EPS3 presents a pentasaccharide repeating unit. Electronic Publication     

Immunochemical analysis of oligosaccharide fragments of O-specific Shigella flexneri polysaccharides

Comparison of inhibitory properties of several synthetic oligosaccharides related to Sh. flexneri O-specific polysaccharides, namely Glc alpha 1-3Rha alpha 1-OMe, Glc alpha 1-3Rha alpha 1-2Rha alpha 1-OMe, Rha alpha 1-2(Glc alpha 1-3)Rha alpha 1-OMe, GlcNAc beta 1-2(Glc alpha 1-3)Rha alpha 1-OMe, and GlcNAc beta 1-2(Glc alpha 1-3) Rha alpha 1-2Rha alpha 1-OMe, using passive haemagglutination reaction demonstrated the tetrasaccharide to possess the highest activity in V; 7,8-anti-7,8 immune system. Among the oligosaccharides under study, only Rha alpha 1-2(Glc alpha 1-3)Rha alpha 1-OMe exhibited moderate anti-V activity.     

STUDIES OF POLYSACCHARIDES FROM THREE EDIBLE SPECIES OF NOSTOC (CYANOBACTERIA) WITH DIFFERENT COLONY MORPHOLOGIES: STRUCTURAL CHARACTERIZATION AND EFFECT ON THE COMPLEMENT SYSTEM OF POLYSACCHARIDES FROM NOSTOC COMMUNE

The cyanobacterium Nostoc commune Vaucher produces quite complex extracellular polysaccharides. The cyanobacterium is nitrogen fixing, and on growing the cyanobacterium in media with and without nitrogen, different types of extracellular polysaccharides were obtained. These were also different from the polysaccharides present in N. commune collected in the field. High pH anion exchange chromatography (HPAEC) of weak acid hydrolysates of the culture-grown material demonstrated that, in this case, HPAEC was useful for comparison of the different polymers. The main differences between the polymers from the field group and the culture-grown samples were the presence of substantial amounts of arabinose, 2- O -methylglucose, and glucuronic acid in the latter. Methylation studies also revealed a difference in the branching points on the glucose units between the field and cultured samples, being 1,4,6 for the first and 1,3,6 for the latter. The field acidic fraction gave, on weak acid hydrolysis and separation on BioGel P2 and HPAEC, 12 oligosaccharide fractions that were isolated and studied by different mass spectroscopy techniques. The structures of the oligosaccharides were determined, and two different series that can originate from two repeating pentamers were identified: GlcA1-4/6GlcM1-4Gal1-4Glc1-4Xyl and GlcA1-4/6Glc1-4Gal1-4Glc1-4Xyl. The difference between these oligosaccharides lies in the methyl substituent on carbon 2 of the glucose unit next to the nonreducing glucuronic acid unit. The polysaccharides from field material were shown to have a strong effect on the complement system.     

Identification by NMR spectroscopy of oligosaccharides obtained by acidolysis of the capsular polysaccharides of a thermal biomass

This study deals with the chemical characterization of a capsular polysaccharide (CPS) produced by a thermal biomass largely comprising the cyanobacterium Mastigocladus laminosus. The sugar moiety of this polymer is composed of seven neutral monosaccharides (Rha, Fuc, Ara, Xyl, Man, GIc, Gal) and two uronic acids (GalA, GIcA). Proteins represent 18% of the dry weight of the CPS. Organic acid substituents (acetate, pyruvate, succinate) were also detected and estimated by high-performance liquid chromatography. The presence of sulfate groups (5% w/w) was observed, which represents a relatively rare feature for cyanobacteria. Acidic hydrolysis of the purified polysaccharide led to the isolation of four oligosaccharidic fractions. NMR spectroscopy studies of two of the four purified oligosaccharides allowed them to be identified as: GlcA(1→2)GalA(1→2)Man and GlcA(1→2)βMan(1→4)βGal(1→2)Rha     

Optimization of water absorbing exopolysaccharide production on local cheap substrates by Bacillus strain CMG1403 using one variable at a time approach

Optimum culture conditions, and carbon and nitrogen sources for production of water absorbing exopolysaccharide by Bacillus strain CMG1403 on local cheap substrates were determined using one variable at a time approach. Carbon source was found to be sole substrate for EPS biosynthesis in the presence of yeast extract that supported the growth only and hence, indirectly enhanced the EPS yield. Whereas, urea only coupled with carbon source could enhance the EPS production but no effect on growth. The maximum yield of EPS was obtained when Bacillus strain CMG1403 was grown statically in neutral minimal medium with 25% volumetric aeration at 30°C for 10 days. Under these optimum conditions, a maximum yield of 2.71±0.024, 3.82±0.005, 4.33±0.021, 4.73±0.021, 4.85±0.024, and 5.52±0.016 g/L culture medium was obtained with 20 g (sugar) of sweet whey, glucose, fructose, sucrose, cane molasses and sugar beet the most efficient one respectively as carbon sources. Thus, the present study showed that under optimum culture conditions, the local cheap substrates could be superior and efficient alternatives to synthetic carbon sources providing way for an economical production of water absorbing EPS by indigenous soil bacterium Bacillus strain CMG1403.     

Effects of temperature and phosphorous concentration on microbial sulfate reduction by Desulfovibrio desulfuricans

The effects of temperature and phosphorous concentration on the rate and the extent of microbial sulfate reduction with lactate as carbon and energy source were investigated for Desulfovibrio desulfuricans. The continuous culture experiments (chemostat) were conducted at pH 7.0 from 12 to 48 degrees C. The maximum specific growth rate (mu(max)) was relatively constant in the range 25 degrees C-43 degrees C and dramatically decreased outside this temperature range. The half-saturation coefficient was minimum at 25 degrees C. Cell yield was highest in the optimum temperature range (35 degrees C-43 degrees C) for growth. Maintenance energy requirements for D. desulfuricans were not significant. Two moles of lactate is consumed for every mole of sulfate reduced, and this stoichiometric ratio is not temperature dependent. Steady state rate and stoichiometric coefficients accurately predicted transient behavior during temperature shifts. The extent of extracellular polymeric substance (EPS) is related to the concentration of phosphorous in the medium. EPS production rate increased with decreased phosphorous loading rate. Failure to discriminate between cell and EPS formation by D. desulfuricans leads to significant overestimates of the cell yield. The limiting C:P ratio for D. desulfuricans was in the range of 400:1 to 800:1.     

预水解发酵碳源对铜绿假单胞菌NY3产鼠李糖脂特性及应用效能的影响研究

发酵碳源对铜绿假单胞菌NY3(Pseudomonas aeruginosa NY3)产鼠李糖脂(Rhamnolipids,Rha)的特性影响较大。研究了利用废弃动物油作为发酵碳源时,其碱预水解和酶预水解对NY3菌发酵产鼠李糖脂产量、产物结构和性能的影响,从碳源水解酸值与水解产物、鼠李糖脂组分结构和实际应用效果进行了研究。碱、酶预水解实验发现,碳源酸值由初始的19.81 mg/g分别提高到72.04 mg/g和73.75 mg/g,气质联用(GC-MS)分析检测结果表明,碱、酶预水解后,碳源均释放7种C14-C18碳链的脂肪酸,鼠李糖脂产量由未预水解的8.28 g/L分别提高到15.35 g/L和17.63 g/L。液质联用(LCMS-IT-TOF)分析结果表明,用未预水解及碱、酶预水解碳源发酵时,NY3菌所产鼠李糖脂中单糖脂含量分别为62.07%、65.67%、87.32%。利用NY3菌在中试条件下处理高浓度石化企业油污泥,发现鼠李糖脂能促进NY3菌去除油污泥中的石油烃,且促进作用强弱顺序为未预水解产Rha碱预水解产Rha酶预水解产Rha。     

Intensification of the exopolysaccharide synthesis by Acinetobacter sp. on an ethanol-glucose mixture: aspects related to biochemistry and bioenergetics

The possibility of intensifying the synthesis of microbial exopolysaccharides (EPS) by a strain of Acinetobacter sp. grown on a mixture of two substrates nonequivalent in terms of bioenergetics (ethanol + glucose) was shown. Based on theoretical calculations of the energy requirements for biomass and EPS synthesis from the energy-deficient substrate (glucose), the supplementary concentration of the energy-excessive substrate (ethanol) was determined that prevents the loss of glucose carbon that occurs when glucose is oxidized to CO2 to obtain energy for the processes of constructive metabolism. This made it possible to increase the efficiency of conversion of the substrate carbon to EPS. The introduction of ethanol into glucose-containing medium at a molar ratio of 3.1:1 allowed the amount of the EPS synthesized to be increased 1.8- to 1.9-fold; their yield relative to biomass increased 1.4- to 1.7-fold, and the yield of EPS relative to the substrate consumed increased 1.5- to 2-fold as compared to growth of the producer on single substrates. These results form the basis for the development of new technologies for obtaining secondary metabolites of practical value with the use of mixed growth substrates.     

Cleavage of the O antigen 4, 5, 12 of Salmonella typhimurium by hydrofluoric acid

The effect of hydrofluoric acid (aqueous 48% HF) upon different lipopolysaccharides (LPS) was studied, employing conditions (48 h at + 4°C) that are commonly used to dephosphorylate LPS. From the LPS of Salmonella typhimurium having the O antigen 4,5,12 almost all of the O-antigenic sugars (Abe, Gal, Glc, Man, Rha) were liberated in dialysable form, whereas the saccharide chains of Salmonella LPS with O antigen 6,7 (Man, Glc, GlcNAc) were resistant to HF. The lability towards HF was shown to be due to the presence of the deoxysugar L-rhamnose in the saccharide backbone of the O antigen 4,5,12, since only Rha was found as the terminal sugar in the corresponding dialysable material. Hydrofluoric acid can thus be used to specifically cleave Rha-containing polysaccharides.     

Influence of Nutritional Factors on the Nature, Yield, and Composition of Exopolysaccharides Produced by Gluconacetobacter xylinus I-2281

The influence of substrate composition on the yield, nature, and composition of exopolysaccharides (EPS) produced by the food-grade strain Gluconacetobacter xylinus I-2281 was investigated during controlled cultivations on mixed substrates containing acetate and either glucose, sucrose, or fructose. Enzymatic activity analysis and acid hydrolysis revealed that two EPS, gluconacetan and levan, were produced by G. xylinus. In contrast to other acetic acid strains, no exocellulose formation has been measured. Considerable differences in metabolite yields have been observed with regard to the carbohydrate source. It was shown that glucose was inadequate for EPS production since most of this substrate (0.84 C-mol/C-mol) was oxidized into gluconic acid, 2-ketogluconic acid, and 5-ketogluconic acid. In contrast, sucrose and fructose supported a 0.35 C-mol/C-mol gluconacetan yield. In addition, growing G. xylinus on sucrose produced a 0.07 C-mol/C-mol levan yield. The composition of EPS remained unchanged during the course of the fermentations. Levan sucrase activity was found to be mainly membrane associated. In addition to levan production, an analysis of levan sucrase's activity also explained the formation of glucose oxides during fermentation on sucrose through the release of glucose. The biosynthetic pathway of gluconacetan synthesis has also been explored. Although the activity of key enzymes showed large differences to be a function of the carbon source, the ratio of their activities remained similar from one carbon source to another and corresponded to the ratio of precursor needs as deduced from the gluconacetan composition.     

Rhizobium trifolii mutant defective in the structure of lipopolysaccharide

Rhizobium trifolii AR182, a mutant resistant to rhizobiophages lysing the parental strain AR5, formed abortive nodules on the clover plant roots. The polyacrylamide gel electrophoresis of the isolated lipopolysaccharide revealed only one band. On the other hand, the lipopolysaccharide isolated from the non-mucoid mutant R. trifolii AR16 showed several, regularly spaced bands in the high molecular weight region. The results suggest that R. trifolii AR182 is a rough (R)-mutant.Abbreviations LPS lipopolysaccharide - EPS exopolysaccharide - CPS capsular polysaccharide - DOC sodium deoxycholate - PAGE polyacrylamide gel electrophoresis - GC-MS gas liquid chromatography-mass spectrometry - KDO 2-keto-3-deoxy-octonic acid - Rha rhamnose - Fuc fucose - Man mannose - Gal galactose - Glc glucose - UA uronic acid     

Cleavage of the O antigen 4,5,12 of Salmonella typhimurium by hydrofluoric acid

The effect of hydrofluoric acid (aqueous 48% HF) upon different lipopolysaccharides (LPS) was studied, employing conditions (48 h at + 4°C) that are commonly used to dephosphorylate LPS. From the LPS of Salmonella typhimurium having the O antigen 4,5,12 almost all of the O-antigenic sugars (Abe, Gal, Glc, Man, Rha) were liberated in dialysable form, whereas the saccharide chains of Salmonella LPS with O antigen 6,7 (Man, Glc, GlcNAc) were resistant to HF. The lability towards HF was shown to be due to the presence of the deoxysugar L-rhamnose in the saccharide backbone of the O antigen 4,5,12, since only Rha was found as the terminal sugar in the corresponding dialysable material. Hydrofluoric acid can thus be used to specifically cleave Rha-containing polysaccharides.