Structural analysis of a novel sialic-acid-containing trisaccharide from Rhodobacter capsulatus 37b4 lipopolysaccharide.

Sialic-acid-containing lipopolysaccharides from Rhodobacter capsulatus 37b4 (S-form lipopolysaccharide), KB-1 (R-type lipopolysaccharide) and Sp 18 (deep R-type lipopolysaccharide) were investigated for the linkage and substitution of sialic acids. Methylation analysis and behaviour towards acid and enzymic hydrolysis indicated a non-reducing terminal location of sialic acids in the R-type lipopolysaccharide of strain Sp 18, whereas an internal, chain-linked location of sialic acids was found in the lipopolysaccharides of strains 37b4 and KB-1. For these latter strains, methylation analysis revealed a substitution of sialic acids by other sugars at position 7 for strain 37b4 and positions 4 and 7 for strain KB-1. In accordance with the chain-linked position of sialic acids, mild hydrolysis of R. capsulatus 37b4 lipopolysaccharide with acetic acid released a trisaccharide with sialic acid at the reducing terminus. Structural investigation of this trisaccharide by methylation analysis, 1H- and 13C-NMR spectroscopy revealed the presence of the disaccharide Gal1-6Glc at the non-reducing end, probably with an alpha-anomeric configuration of the galactose residue, i.e. melibiose, beta-glycosidically linked to position 7 of sialic acid. Therefore the structure Gal alpha 1-6Glc beta 1-7Neu5Ac is proposed for this core oligosaccharide from R. capsulatus 37b4 lipopolysaccharide.     

Detection of capsule and slime polysaccharide layers in two strains of Rhodopseudomonas capsulata

A capsule and slime were visualized electronmicroscopically in Rhodopseudomonas capsulata strain St. Louis (=ATCC 23782) and strain Sp 11 after pre-incubation of the cells in the homologous O/K antisera. The slime consists of loosely associated material surrounding the cell in irregular distribution. The capsule is directly adjacent to the cell wall and has a constant thickness of 75–85 nm in strain St. Louis and 30–40 nm in strain Sp 11. The capsule has a fibrillar fine-structure with radial orientation to the cell surface. In contrast to the slime, it is not removed from the cells by washing with saline.An acidic polysaccharide fraction was obtained from both strains by cetavlon fractionation of hot phenol-water extracts. The composition is strain-specific: the relative amounts of the common sugars found, i.e. rhamnose, galactose, glucose, glucosamine and galacturonic acid are different, the fraction from strain Sp 11 contains additionally fucose, 3-amino-3,6-dideoxygalactose, an unknown amino sugar and an unknown acidic component. Whether the polysaccharides of these fractions are in fact the slime or capsular substances remains to be established.     

Studies on the lipopolysaccharide of a virulent and an avirulent strain of Vibrio vulnificus.

Vibrio vulnificus is a marine bacterium associated with both primary septicemias and wound infections in humans. The lipopolysaccharides of a virulent and an avirulent strain of Vibrio vulnificus were compared with respect to their chemical constituents and electrophoretic characteristics. 2-Keto-3-deoxyoctonic acid, a normal constituent of the lipopolysaccharide of typical Enterobacteriaceae, was not found in the lipopolysaccharide of either strain. Hexadecenoate (C16:1) was the predominant fatty acid of the lipid A moiety of the lipopolysaccharides and of the membrane phospholipids of both strains. Hydroxy fatty acids composed 44% of the total fatty acids of the lipid A of the avirulent and 40% of those in the virulent strain. In addition, odd-numbered fatty acids were detected in both lipopolysaccharides. The electrophoretic profile was similar for both strains, but demonstrated no "ladder-like" pattern characteristic of "smooth" lipopolysaccharides. The result of this study showed no significant differences between the lipopolysaccharides of the virulent and avirulent strains of Vibrio vulnificus. The possible role for lipopolysaccharide in pathogenesis of Vibrio vulnificus infections is discussed.     

Characterization of the cell wall and outer membrane of Rhodopseudomonas capsulata.

Sucrose density gradient centrifugation of cell envelopes of chemotrophically grown cells of Rhodopseudomonas capsulata St. Louis (= ATCC 23782) resulted in the separation of a cytoplasmic membrane from a cell wall fraction (buoyant densities, 1.139 and 1.215 g/cm3, respectively). The cell wall fractions (untreated or Triton extracted) contained peptidoglycan- and lipopolysaccharide-specific components. Their neutral sugar content, mainly rhamnose and galactose, was high (250 and 100 micrograms/mg [dry weight] of material) due to a non-lipopolysaccharide polymer. The fatty acid content was low (less than or equal to 60 micrograms/mg [dry weight] of material), and half of it was contributed by lipopolysaccharide (3-OH-C10:0, C12:1, and 3-oxo-C14:0). The predominant other fatty acid was C18:1. An outer membrane fraction, obtained by lysozyme treatment of the Triton-extracted cell wall, showed essentially the same chemical composition except for almost complete removal of peptidoglycan. Saline extraction (0.9% NaCl, 37 degrees C, 2 h) removed a lipopolysaccharide-protein(-phospholipid?) complex from whole cells of R. capsulata St. Louis. The polypeptide patterns of the cell wall and outer membrane as revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis comprised 20 to 25 different polypeptides (most of them very faint) and were dominated by a single, heat-modifiable major protein (Mr 69,000 after solubilization below 60 degrees C; Mr 33,000 at temperatures above 70 degrees C).     

Different polysaccharides in the external layers (capsule and slime) of the cell envelope of Rhodopseudomonas capsulata Sp11

Two different acidic polysaccharides (I and II) were detected in the external cell envelope layers (slime and capsule) of Rhodopseudomonas capsulata Sp11. Polysaccharide I contains rhamnose, fucose, glucosamine and an unknown acidic sugar, it represents the slime material of the strain. Polysaccharide II contains rhamnose, galactose, 3-amino-3,6-dideoxygalactose, an unknown amino sugar and galacturonic acid, it represents very likely the capsule of R. capsulata Sp11. Polysaccharide I has a serological specificity different from that of polysaccharide II as shown by immunoprecipitation using antisera against living cells. Polysaccharide II, but not polysaccharide I, reacts in antiserum against heat-treated cells (100 degrees C, 2.5 h). Whole cells are agglutinated in the antisera against living but not in those against heat-treated cells.     

Chemical characterization of effective and ineffective strains of Rhizobium leguminosarum bv. viciae

Chemical composition of lipopolysaccharide (LPS) isolated from an effective (97) and ineffective (87) strains of R. l. viciae has been determined. LPS preparations from the two strains contained: glucose, galactose, mannose, fucose, arabinose, heptose, glucosamine, galactosamine, quinovosamine, and 3-N-methyl-3,6-dideoxyhexose, as well as glucuronic, galacturonic and 3-deoxyoctulosonic acid. The following fatty acids were identified: 3-OH 14:0, 3-OH 15:0, 3-OH 16:0, 3-OH 18:0 and 27-OH 28:0. The ratio of 3-OH 14:0 to other major fatty acids in LPS 87 was higher that in LPS 97. SDS/PAGE profiles of LPS indicated that, in lipopolysaccharides, relative content of S form LPS I to that of lower molecular mass (LPS II) was much higher in the effective strain 97 than in 87. All types of polysaccharides exo-, capsular-, lipo, (EPS, CPS, LPS, respectively) examined possessed the ability to bind faba bean lectin. The degree of affinity of the host lectin to LPS 87 was half that to LPS 97. Fatty acids (FA) composition from bacteroids and peribacteroid membrane (PBM) was determined. Palmitic, stearic and hexadecenoic acids were common components found in both strains. There was a high content of unsaturated fatty acids in bacteroids as well as in PBM lipids. The unsaturation index in the PBM formed by strain 87 was lower than in the case of strain 97. Higher ratio of 16:0 to 18:1 fatty acids was characteristic for PMB of the ineffective strain.     

Chemical composition of lipopolysaccharide from Azospirillum lipoferum

Abstract The lipopolysaccharide isolated from Azospirillum lipoferum strain SpBr17 (ATCC29709) was proven to be composed from 7 neutral sugars, two of which, rhamnose and glucose, were the major constituents. Two heptoses, l -glycero- d -mannoheptose and d -glycero- l -mannoheptose were identified. Among 8 fatty acids isolated from the lipopolysaccharide only 3-hydroxypalmitic acid was amide-bound. The approximate molar ratios of the constituents 3-deoxy- l -mannooctulosonic acid : glucosamine : amide-linked fatty acids : ester-linked fatty acids : phosphate were 0.8 : 4 : 2 : 4 : 2.5.     

Lipophilic O-antigens in Rhodospirillum tenue.

Lipopolysaccharides of eight wild-type strains of the phototrophic bacterium Rhodospirillum tenue have been analyzed. All of the lipopolysaccharides are highly lipophilic. The compositions of preparations obtained by the phenol-water or by the phenol-chloroform-petroleum ether procedure are very similar. The polysaccharide moiety, obtained by mild acid hydrolysis of lipopolysaccharide, consists mainly of aldoheptoses: L-glycero-D-mannoheptose is present in all strains, whereas D-glycero-D-mannoheptose is an additional constituent in some strains. Galactosaminuronic acid and two unknown ninhydrin-positive components were detected in the lipopolysaccharides of six strains. Spermidine and putrescine are present in large amounts in a salt-like linkage in the lipopolysaccharides from three strains. 2-Keto-3-deoxyoctonate forms the linkage between the polysaccharide moiety and lipid A. The lipid A fraction contains all the glucosamine and all the D-arabinose present in the lipopolysaccharide. D-Arabinose is an invariable constituent of the lipid A from the Rhodopseudomonas tenue lipopolysaccharides investigated. The principal fatty acids are beta-hydroxycapric, myristic, and palmitic acids. The isolated R. tenue lipopolysaccharides (O-antigens) react with rabbit antisera prepared against homologous cells. The titers in passive hemagglutination are low, similar to those found with enterobacterial R-lipopolysaccharides. R. tenue O-antigens containing only L-glycero-D-mannoheptose and those containing both the L- and D-epimers of glycero-D-mannoheptose could not be differentiated by serological means.     

Lipopolysaccharides from six strains of Acetobacter diazotrophicus

Abstract Lipopolysaccharides from six nitrogen-fixing strains of Acetobacter diazotrophicus (PR2, PAL3, PAL5, PR4, PR14, PR20), isolated from sugarcane, were purified by phenol-water extraction and ultracentrifugation. The relatively large molecular mass observed by SDS-PAGE indicated that the lipopolysaccharides of each strain possessed an O-side chain. Analysis of each lipopolysaccharide by colorimetric assays and by gas liquid chromatography/mass spectrometry combination showed that the core and lipid A composition was similar for all strains, containing 3-deoxy-d-manno-2-octulosonic acid, glucosamine and fatty acid (16-0, 3-OH-14, 2-OH-16:0, 3-OH-16:0). The neutral sugar composition showed the predominance of 6-deoxy-hexose (rhamnose and fucose) and ribose, in comparison with hexose (glucose, galactose, mannose). The presence of 6-deoxy-hexose and ribose containing O-side chains is discussed as a way of discriminating A. diazotrophicus from other Acetobacter species.     

Biochemical studies on the cell wall lipopolysaccharides (O-antigens) of Vibrio cholerae 569 B (Inaba) and El-tor (Inaba).

Lipopolysaccharides were isolated from the cell walls of Vibrio cholerae 569 B (Inaba) and El-tor (Inaba). Chemical analysis revealed the presence of glucose, fructose, mannose, heptose, rhamnose, ethanolamine, fatty acids and glucosamine. The lipopolysaccharides do not contain 2-keto-3-deoxyoctonate, the typical linking sugar of polysaccharide and lipid moieties of enterobacterial lipopolysaccharides. Galactose, a typical core polysaccharide component of many gram-negative bacteria was also absent from lipopolysaccharides of these organisms. By hydrolysis in 1% acetic acid, the lipopolysaccharides have been separated into a polysaccharide part (degraded polysaccharide) and a lipid part (lipid A). Components of degraded polysaccharide and lipid A moiety were identified and determined. The lipid A fractions contained fatty acids, phosphorus and glucosamine. All the neutral sugars detected in lipopolysaccharides were shown to be the constituents of its polysaccharide moiety. The fatty acid analysis of lipopolysaccharide and lipid A showed the presence of both hydroxy and non hydroxy acids. They were different from those of lipids extracted from cell walls before the extraction of lipopolysaccharides. 3-Hydroxylauric and 3-hydroxymyristic acids predominated in lipopolysaccharide and lipid A of Vibrio cholerae and El-tor (Inaba).     

Composition of the cell wall of the phage resistant mutantRhodopseudomonas capsulata St. Louis RC1-

A mutant ofRhodopseudomonas capsulata St. Louis (R. capsulata St. Louis RC1^-), resistant against the bacteriophage RC1, was isolated and its cytoplasmic membrane and cell wall fractions (buoyant densities on sucrose density gradient centrifugation: 1.123 and 1.222 g/cm³, respectively) were obtained. Different from the wild type strain, the cell wall fraction of the mutant lacked galactose. Galactose is a characteristic component of the capsule polysaccharide ofR. capsulata St. Louis. There were no differences in lipopolysaccharide and peptidoglycan compositions as well as in polypeptide patterns of the cell wall fractions between mutant and wild-type cells. Thus, the lack of a firmly bound capsule inR. capsulata St. Louis RC1^- was the only difference found.     

The lipopolysaccharide from Pseudomonas aeruginosa NCTC 8505. Structure of the O-specific polysaccharide

Structural studies have been carried out on the O-specific fraction from the lipopolysaccharide of Pseudomonas aeruginosa NCTC 8505, Habs serotype 03. The O-specific polysaccharide has a tetrasaccharide repeating-unit containing residues of L-rhamnose (Rha), 2-acetamido-2-deoxy-D-glucose (GlcNAc), 2-acetamido-2-deoxy-L-galacturonic acid (GalNAcA), and 2,4-diacetamido-2,4,6-trideoxy-D-glucose (BacNAc2). The following structure has been assigned to the repeating-unit: leads to 3)Rhap(beta 1 leads to 6)GlcpNAc(alpha 1 leads to 4)GalpNAcA(alpha 1 leads to 3)BacpNAc2(alpha 1 leads to. The parent lipopolysaccharide is a mixture of S, R, and SR species, and its high phosphorus content is partly due to the presence of triphosphate residues, as found for other lipopolysaccharides from P. aeruginosa. In addition to phosphorus, heptose, a 3-deoxyoctulosonic acid, and amide-bound alanine, the core oligosaccharide contains glucose, rhamnose, and galactosamine (molar proportions 3:1:1). The rhamnose and part of the glucose are present as unsubstituted pyranoside residues: other glucose residues are 6-substituted.     

Characterization of lipopolysaccharides from Pseudomonas fluorescens IMB 2108 (biovar II) and IMB 2111 (biovar IV) with O-chains represented by alpha-glucan

Results of studies of the structurally unique O-chains of lipopolysaccharides, which were isolated from the dry biomass of Pseudomonas fluorescens IMB 2108 (biovar II) and IMB 2111 (biovar IV) by the Westphal technique and purified by repeated ultracentrifugation, are reported. The bulk of the lipopolysaccharide preparations contained S- and R-molecules at an average molar ratio of 1: 2. The main components of the hydrophobic moiety of lipid A were 3-hydroxydecanoic, 2-hydroxydodecanoic, 3-hydroxydodecanoic, dodecanoic, hexadecanoic, and octadecanoic acids, as well as hexadecenoic and octadecenoic acids. Glucosamine and phosphoethanolamine were identified as components of the hydrophilic moiety of lipid A. The degree of lipid A phosphorylation amounted to 3-4%. Fractions of the core oligosaccharide contained glucose, galactose, mannose, rhamnose, arabinose, glucosamine (only in strain IMB 2108), alanine, phosphoethanolamine, phosphorus, and 2-keto-3-deoxyoctulosonic acid (KDO). Heptose was present in trace amounts. O-specific polysaccharide chains were represented by a linear polymer of D-glucose units, which were linked together via alpha-(1,4) glycoside bonds. The existence of P. fluorescens strains that have alpha-1,4-glucan as the O-chain of their lipopolysaccharides has not been described before.     

Studies on the chemical composition of lipopolysaccharide from Neisseria meningitidis group B.

A lipopolysaccharide was isolated from Neisseria meningitidis group B by phenol/water extraction and purified by differential ultracentrifugation. This preparation exhibited endotoxic properties as shown by the limulus-lysate assay. Mild acid hydrolysis of the lipopolysaccharides yielded a lipid A fraction and a polysaccharide fraction. The lipid A fraction contained fatty acids, phosphorus and glucosamine. Analysis of the polysaccharide fraction revealed the presence of glucose, galactose, glucosamine, 2-keto-3-deoxyoctonic acid and phosphorus. There was no heptose.     

Chemical studies on the lipopolysaccharide of Rhizobium meliloti 10406 and its lipid A region

The structure of the lipopolysaccharide from Rhizobium meliloti 10406, a derivative of the wild-type strain MVII-1, was examined. The compositional analysis of its polysaccharide moiety demonstrated lack of heptose(s), but high contents in glucose, galacturonic acid and 2-keto-3-deoxy-octonate (dOclA) as characteristic features. The lipid A moiety consisted of a -1,6 linked glucosamine disaccharide carrying ester (at C-4) and glycosidically (at C-1) linked phosphate residues, both present exclusively as monoester phosphates but not as phosphodiesters. Ester- and amidelinked 3-hydroxy fatty acids were mostly present as non-3-O-acylated residues. Laser desorption mass spectrometry (LD-MS) revealed heterogeneity in the fatty acid substitution, as was also indicated by the non-stoichiometric ratios obtained by quantitative fatty acid analysis. The predominating lipid A structure contained at the reducing glucosamine residue ester-linked 3-hydroxy-tetradecanoic acid (3-OH-14:0) and amide-linked 3-OH-18:0, or 3-OH-18:1, respectively. The distal (non-reducing) glucosamine carried ester-bound the recently discovered 27-hydroxyoctacosanoic acid and 3-OH-14:0 and, as amide-linked fatty acid, mostly 3-hydroxy-stearic acid (3-OH-18:0).The isolated lipopolysaccharide exhibited a high extent of lethal toxicity in galactosamine-treated mice, comparable to that of enterobacterial lipopolysaccharide. The structural relationship of LPS and lipid A of Rhizobium meliloti to other rhizobial lipopolysaccharides and lipid A's with respect to questions of taxonomy and of phylogenetic relationships will be discussed.Abbreviations LPS lipopolysaccharide - dOclA 3-deoxy-D-mannooctulosonic acid (KDO) - GalA galacturonic acid - DOC sodium deoxycholate - PAGE polyacrylamide gel electrophoresis - LD-MS laser desorption-mass spectrometry     

fbc operon, encoding the Rieske Fe-S protein cytochrome b, and cytochrome c1 apoproteins previously described from Rhodopseudomonas sphaeroides, is from Rhodopseudomonas capsulata

Detailed comparison of the 'Rhodopseudomonas sphaeroides GA' strain used by Gabellini et al. (1985) with genuine R. sphaeroides and R. capsulata strains indicated that the previously reported fbc operon of R. sphaeroides (Gabellini and Sebald, 1986) encoding the structural genes for the Rieske Fe-S protein, cytochrome b and cytochrome c1 subunits of the ubiquinol:cytochrome c2 oxidoreductase, is not from R. sphaeroides, but is rather from a strain of R. capsulata. Consequently, the genuine bc1 genes from R. sphaeroides were cloned using corresponding R. capsulata genes as probes, and a partial nucleotide sequence for the Rieske Fe-S protein of R. sphaeroides was determined and compared with that of R. capsulata.     

Cell surface polysaccharides from Bradyrhizobium japonicum and a nonnodulating mutant.

The cell surface polysaccharides of wild-type Bradyrhizobium japonicum USDA 110 and a nonnodulating mutant, strain HS123, were analyzed. The capsular polysaccharide (CPS) and exopolysaccharide (EPS) of the wild type and the mutant strain do not differ in their sugar composition. CPS and EPS are composed of mannose, 4-O-methylgalactose/galactose, glucose, and galacturonic acid in a ratio of 1:1:2:1, respectively. H nuclear magnetic resonance spectra of the EPS and CPS of the wild type and mutant strain are very similar, but not identical, suggesting minor structural variation in these polysaccharides. The lipopolysaccharides (LPS) of the above two strains were purified, and their compositions were determined. Gross differences in the chemical compositions of the two LPS were observed. Chemical and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses indicated that strain HS123 is a rough-type mutant lacking a complete LPS. The LPS of mutant strain HS123 is composed of mannose, glucose, glucosamine, 2-keto-3-deoxyoctulosonic acid, and lipid A. The wild-type LPS is composed of fucose, xylose, arabinose, mannose, glucose, fucosamine, quinovosamine, glucosamine, uronic acid, 2-keto-3-deoxyoctulosonic acid, and lipid A. Preliminary sugar analysis of lipid A from B. japonicum identified mannose, while traces of glucosamine were detected. 3-Hydroxydodecanoic and 3-hydroxytetradecanoic acids formed a major portion of the fatty acids in lipid A. Lesser quantities of nonhydroxylated 16:0, 18:0, 22:0, and 24:0 acids also were detected.     

Analysis of the cell wall and lipopolysaccharide of Spirillum serpens.

Isolated walls of Spirillum serpens VHA contained lipid, lipopolysaccharide, and protein in amounts similar to those of other gram-negative organisms. The loosely bound lipids consisted mainly of phosphatidylethanolamine, lyso-phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol. Lipopolysaccharide was tightly bound to the wall and could only be removed in a substantial amount after digestion of the wall with Pronase. The lipopolysaccharide contained L-glycero-D-mannoheptose, rhamnose, glucosamine, ethanolamine, and phosphate in common with many of the lipopolysaccharides isolated from the Enterobacteriaceae. However, 2-keto-3-deoxyoctonic acid was not detected. Several unidentified sugars were present. The fatty acid composition resembled that found in lipopolysaccharides isolated from various pseudomonads. Two major regions were identified in the polysaccharide moiety, one apparently corresponding to the core polysaccharide and the other corresponding to the side-chain polysaccharide as in enterobacterial and pseudomonad lipopolysaccharides. The side chains were obtained as low-molecular-weight material and their structure was partially elucidated by the isolation and partial characterization of N-acetylglucosaminyl-(1 leads to 4)-rhamnose.     

Distribution and composition of lipopolysaccharides from mycoplasmas.

Polymeric carbohydrates containing glycerol and fatty acids were isolated from whole cells and membranes of mycoplasmas by hot aqueous phenol extraction and gel filtration. Lipopolysaccharides were found to occur in four species of Acholeplasma, two of Anaeroplasma, and in Mycoplasma neurolyticum. None were detected in Spiroplasma citri or in five species of Mycoplasma. All lipopolysaccharides contained both neutral and N-acylated amino sugars in ratios varying from 1:1 to 3:1. The neutral sugars found in varying distribution were glucose, galactose, and mannose. The amino sugars included fucosamine, an unidentified deoxyhexosamine, galactosamine, and glucosamine. Fucosamine and glucose were the only sugars common to all lipopolysaccharides. The fatty acids were similar to those found in the lipids of each organism.     

Investigation of lipopolysaccharides from Sinorhizobium meliloti SKHM1-188 and two of its mutants with decreased nodulation competitiveness

A comparative study of the lipopolysaccharides (LPS) isolated from Sinorhizobium meliloti SKHM 1-188 and two its LPS-mutants (Th29 and Ts22) with sharply decreased nodulation competitiveness was conducted. Polyacrylamide gel electrophoresis with sodium dodecyl sulfate revealed two forms of LPS in all the three strains: a higher molecular-weight LPS1, containing O-polysaccharide (O-PS), and a and lower molecular-weight LPS2 without O-PS. However, the LPS1 content in mutants was significantly smaller than in the parent strain. The LPS of the strains studied contained glucose, galactose, mannose, xylose, three nonidentified sugars--X1 (TGlc 0.53), X2 (TGlc 0.47), and X3 (TGlc 0.43), glucosamine, and ethanolamine, while the LPS of S. meliloti SKHM1-188 additionally contained galactosamine, glucuronic and galacturonic acids, and 2-keto-3-deoxyoctulosonic acid (KDO), as well as fatty acids, such as 3-OH C14:0, 3-OH C15:0, 3-OH C16:0, 3-OH C18:0, nonidentified hydroxy X (T3-OH C14:0 1.33), C18:0, and unsaturated C18:1 fatty acids. The LPS of both mutants were similar in the component composition but differed from the LPS of the parent strain by a lower X2, X3, and 3-OH C 14:0 content and a higher KDO, C18:0, and hydroxy X content. The LPS of all the strains were subjected to mild hydrolysis with 1% acetic acid and fractionated on a column with Sephadex G-25. The higher molecular weight fractions (2500-4000 Da) contained a set of sugars typical of intact LPS and, supposedly, corresponded to the LPS polysaccharide portion (PS1). In the lower molecular weight fractions (600-770 Da, PS2), glucose and uronic acids were the major components; galactose, mannose, and X1 were present in smaller amounts. The PS1/PS2 ratio for the two mutants was significantly lower than for strain SKHM1-188. The data obtained show that the amount of O-PS-containing molecules (LPS1) in the heterogeneous lipopolysaccharide complex of the mutants was smaller than in the SKHM1-188 LPS; this increases the hydrophobicity of the cell surface of the mutant bacteria. This supposedly contributes to their nonspecific adhesion on the roots of the host plant, thus decreasing their nodulation competitiveness.