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PubMed1976

Mode of insertion of lipopolysaccharide into the outer membrane of escherichia coli.

A mutant of Escherichia coli that lacks uridine 5'-diphosphate galactose-4-epimerase makes lipopolysaccharide with less carbohydrate than the parent, unless galactose is present during growth. Carbohydrate is dense, and the outer membrane, which contains lipopolysaccharide, was found to be denser when isolated from cells grown with galactose then when galactose was omitted. Cells given galactose after growth in its absence rapidly formed dense regions within the outer membrane that disappeared when galactose was removed. These results indicate that lipopolysaccharide enters the outer membrane nonrandomly at a minimum of 10 to 22 discrete "insertion points." Isopycnic centrifugation provides a method for isolating these regions.

Carbohydrate Epimerases↗

PubMed1979

Immuno-electron microscopic localization of lipopolysaccharide antigens on ultrathin sections of Salmonella typhimurium.

Lipopolysaccharide antigens were demonstrated on ultrathin sections of styrene-embedded Salmonella typhimurium by direct postembedding staining with ferritin-labeled antibodies. The antigenicity, partially masked in the embedding process, could be satisfactorily recovered by treatment of ultrathin sections with nonspecific protease. As judged from the reaction site of the ferritin-labeled antibodies, the lipopolysaccharides were localized in two zones. The broader zone of densely distributed ferritin molecules was superimposed over the whole outer cellwall, and a smaller zone revealing antigenicity was found over the cell membrane, which strongly supports the concept that the latter is the site of synthesis of lipopolysaccharides. The well-defined labeled areas between these two antigenic zones may be the routes whereby the synthesized polysaccharide molecules reach the cell wall.

Antigen-Antibody Reactions↗

PubMed1980

Asymmetric localization of lipopolysaccharides on the outer membrane of Salmonella typhimurium.

Treatment of intact cells of Salmonella typhimurium with galactose oxidase (EC 1.1.3.9) resulted in an extensive oxidation of the susceptible galactose residues in the lipopolysaccharides. Comparison with the extent of oxidation in isolated lipopolysaccharides indicated that most lipopolysaccharide molecules were located in the outer leaflet of the outer membrane in intact cells.

Cell Membrane↗

PubMed1980

Nature, type of linkage, quantity, and absolute configuration of (3-hydroxy) fatty acids in lipopolysaccharides from Bacteroides fragilis NCTC 9343 and related strains.

The main fatty acids present in lipopolysaccharides from Bacteroides fragilis NCTC 9343 were identified as 13-methyl-tetradecanoic, D-3-hydroxypentadecanoic, D-3-hydroxyhexadecanoic, D-3-hydroxy-15-methyl-hexadecanoic, and D-3-hydroxyheptadecanoic acids. Of these, 13-methyl-tetradecanoic acid is exclusively ester bound, and 3-hydroxy-15-methyl-hexadecanoic acid is exclusively involved in amide linkage. The other 3-hydroxy fatty acids are both ester and amide bound. All 3-hydroxy fatty acids possess the D configuration, and the 3-hydroxyl group of ester-linked 3-hydroxy fatty acids is not substituted. Lipopolysaccharides of related Bacteroides species (B. thetaiotaomicron, B. ovatus, B. distasonis, and B. vulgatus) showed a fatty acid spectrum with both similar and distinct features compared to that of B. fragilis lipopolysaccharides.

Bacteroides↗

PubMed1981

Gene rfaH, which affects lipopolysaccharide core structure in Salmonella typhimurium, is required also for expression of F-factor functions.

Mutations in gene rfaH of Salmonella typhimurium at 84 units on the linkage map make lipopolysaccharide of chemotypes Ra, Rb2, Rb3, and Rc (A. A. Lindberg and C. G. Hellerqvist, J. Gen. Microbiol, 116:25--32, 1980). F-factor expression in RfaH- strains was reduced in the following properties when compared with RfaH+ strains: transfer of Flac, number of phage f2 infective centers, lysis by and propagation of phages f2 and M13, proportion of cells with visible F-pili, and formation of mating aggregates with F- cells. Inhibition of multiplication of Br60, a female-specific phage, was not reduced in RfaH- Flac strains. Plasmid transfer from RfaH- strains was reduced for Inc groups FI, FII, and T, unaffected for Inc groups beta, I alpha, L, N, P, and W. and increased for Inc group M when compared with plasmid transfer from RfaH+ strains. Reduced F-factor function in RfaH- strains was not due to defective lipopolysaccharide since strains with mutations in other rfa genes were unaffected in plasmid transfer. Gene rfaH appears to be homologous with gene sfrB in Escherichia coli K-12, which maps at the same location, influences F-factor function, and affects synthesis of lipopolysaccharide. The gene product of sfrB has been proposed to be a transcription antiterminator.

Coliphages↗

PubMed1981

Role of lipopolysaccharide in the receptor function for bacteriophage TuIb in Escherichia coli.

Bacteriophage TuIb required lipopolysaccharide in addition to the OmpC trimer as a receptor component. Both the fatty acid and polysaccharide regions of lipopolysaccharide were shown to participate in the receptor function. The roles of lipopolysaccharide and outer membrane proteins in the receptor function for T-even type bacteriophages are discussed.

Bacterial Outer Membrane Proteins↗

PubMed1982

Colicin A receptor: role of two Escherichia coli outer membrane proteins (OmpF protein and btuB gene product) and lipopolysaccharide.

ompF cells were completely resistant to colicin A, whereas btuB cells were partially resistant. The OmpF protein, in the presence of added lipopolysaccharide, inactivated colicin A. This inactivation was enhanced by added btuB gene product, btuB gene product with lipopolysaccharide did not inactivate colicin A. These data, together with the observation that vitamin B12 protected btuB+ cells from the killing effect of colicin A, suggest that the colicin A receptor in Escherichia coli K-12 is composed of the OmpF protein, the btuB gene product, and lipopolysaccharide.

Adsorption↗

PubMed1985

Cloning of rfaG, B, I, and J genes for glycosyltransferase enzymes for synthesis of the lipopolysaccharide core of Salmonella typhimurium.

R-prime plasmids carrying the pyrE-rfa-cysE region of the chromosome of Salmonella typhimurium were isolated by using the vector pULB113 (RP4::mini-Mu). One of the R-prime plasmids was used as a source of DNA to clone the rfa genes for lipopolysaccharide synthesis to pBR322. The following three hybrid plasmids were constructed: pKZ15, with a 4.0-kilobase EcoRI fragment of S. typhimurium DNA, containing the rfaG gene; pKZ27, a 9-kilobase BglII fragment with the rfaG, rfaB, and rfaI genes; and pKZ26, a 7.7-kilobase HindIII fragment with the rfaG, rfaB, rfaI, and rfaJ genes. We propose that these cloned genes code for four glycosyltransferases used for synthesis of the lipopolysaccharide core region (rfaG for glucosyltransferase I; rfaI for galactosyltransferase I; rfaB for galactosyltransferase II; and rfaJ for glucosyltransferase II). For all four genes, mutants which lacked the appropriate enzyme activity were complemented by the plasmids to give completed core lipopolysaccharide with O (somatic) side chains; for rfaG, rfaB, and rfaI, mutants gave restored or even amplified levels of the appropriate glycosyltransferase in in vitro assays. We show that the order of genes in the region is pyrE-rfaG-(rfaB-rfaI)-rfaJ-rfaL-rfaF -cysE.

Cloning, Molecular↗

PubMed1985

Phospholipids and lipopolysaccharide of Aeromonas hydrophila.

The phospholipids and lipopolysaccharide of Aeromonas hydrophila were characterized. Phosphatidylethanolamine and phosphatidylglycerol were the major phospholipid components. The outer membrane contained more phosphatidylethanolamine and less phosphatidylglycerol than the inner membrane, and the phospholipids of the outer membrane contained a higher proportion of saturated fatty acids. Only four fatty acids (C14:0, C16:0, C16:1, and C18:1) were found in the phospholipids. The lipopolysaccharide of A. hydrophila did not contain the eight-carbon sugar 3-deoxyoctulosonic acid nor did it contain C16:0, both of which are typical constituents of the lipopolysaccharide of many other species.

Aeromonas↗

PubMed1988

Unmasking of bacteriophage Mu lipopolysaccharide receptors in Salmonella enteritidis confers sensitivity to Mu and permits Mu mutagenesis.

The human pathogen Salmonella enteritidis 3b was found to be highly resistant to phage P22 and Mu derivatives. The Mu sensitivity (musA1) allele from Salmonella typhimurium could be transferred to S. enteritidis 3b at low frequency by cotransduction with hisG::Tn10. Sensitivity to Mu resulted in a large reduction in the number of lipopolysaccharide core-region oligosaccharides that were substituted with O-antigen polysaccharide. The residual high-molecular-weight lipopolysaccharide appeared to be a hybrid displaying O antigens which were immunologically related to those of S. typhimurium and not to those of S. enteritidis. Consequently, Mu d1(Ap lac) could then be transduced into Mus strains forming stable lysogens. On temperature induction, Mu transposition could easily be used to generate mutations in genes coding for cell surface antigens including fimbriae, lipopolysaccharide, and flagella.

Antigens, Surface↗

PubMed1989

Genetic derepression of a developmentally regulated lipopolysaccharide antigen from Rhizobium leguminosarum 3841.

Monoclonal antibody AFRC MAC 203 recognizes a developmentally regulated lipopolysaccharide antigen in Rhizobium leguminosarum bv. viciae 3841. Transposon-induced mutants that constitutively expressed MAC 203 antigen were isolated. These strains were morphologically normal, showed no gross abnormalities in lipopolysaccharide size distribution on sodium dodecyl sulfate-polyacrylamide gels, and induced normal nitrogen-fixing nodules. However, the mutants lacked lipopolysaccharide epitopes recognized by another rat monoclonal antibody, AFRC MAC 281, suggesting that the corresponding epitopes may be interconverted or share a common precursor. In conjugational crosses, the transposon insertion associated with both the loss of MAC 281 antigen and the constitutive expression of MAC 203 antigen showed linkage to the chromosomal rif allele. A derivative of strain 3841 with a deletion spanning the nod-fix region of the symbiotic plasmid showed no altered expression pattern for MAC 203 antigen, suggesting that the relevant genetic determinants map to genomic sites that are not associated with nifA or any known genes on the symbiotic plasmid.

Antibodies, Monoclonal↗

PubMed1990

Detection of lipopolysaccharides by ethidium bromide staining after sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

A rapid and easy method for staining lipopolysaccharides with ethidium bromide is described. Lipopolysaccharides could be visualized by ethidium bromide with almost the same sensitivity as found with the silver-staining method in less than 30 min. The ethidium bromide-staining method was particularly suitable for staining lipopolysaccharides possessing acidic O-specific polysaccharides, which were poorly visualized by silver staining.

Electrophoresis, Polyacrylamide Gel↗

PubMed1991

Analysis of the host ranges of transposon bacteriophages Mu, MuhP1, and D108 by use of lipopolysaccharide mutants of Salmonella typhimurium LT2.

The lipopolysaccharide receptors for the mutator bacteriophages Mu, MuhP1, and D108 were investigated with lipopolysaccharide mutants of Salmonella typhimurium LT2. Mu adsorbed only to mutants lacking the terminal O antigen but retaining the main chain sugars of the core; the side chain N-acetylglucosamine was not required. MuhP1 and D108 adsorbed partially to cells with the same receptors but adsorbed well only to cells with shorter lipopolysaccharides of the Rc and Rd1 chemotypes.

Acetylglucosamine↗

PubMed1991

Regulation by a novel protein of the bimodal distribution of lipopolysaccharide in the outer membrane of Escherichia coli.

We report on the cloning and characterization of the rfb gene cluster of the O75 lipopolysaccharide from a urinary tract isolate of Escherichia coli. Deletion cloning defined the minimum region of DNA that expressed the O75 antigen in E. coli host strains to be on a 12.4-kb insert. However, the E. coli strain expressing this region did not produce a polymerized O chain as detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining. A slightly larger DNA clone of 13.4 kb produced a polymerized O chain in E. coli S phi 874 but was found to be abnormal in its distribution over the surface membrane. Normal wild-type E. coli, as with Salmonella spp., has a bimodal distribution of the lipopolysaccharide on the surface which is seen as an abundance of long and short O chains attached to the lipid A-core structure. We found in a region adjacent to the cloned rfb region, and on the opposite side from where the putative polymerase (rfc) is encoded, a novel protein of 35.5 kDa expressed from a 1.75-kb DNA fragment. This protein was shown to complement in trans the E. coli strains carrying plasmids that expressed abnormal, unregulated lipopolysaccharides. The expression of these complemented strains was bimodal in distribution. Mutation of the gene encoding this protein destroyed its ability to regulate O-chain distribution. We propose to call this regulator gene rol, for regulator of O length.

Antigens, Bacterial↗

PubMed1991

Lipopolysaccharide structure required for in vitro trimerization of Escherichia coli OmpF porin.

Deep rought mutants, which produce very defective lipopolysaccharides, are unable to export normal levels of porins into the outer membrane. In this study, we showed that lipopolysaccharides from such mutants were also unable to facilitate the trimerization, in vitro, of monomeric OmpF porin secreted by spheroplasts of Escherichia coli B/r. In contrast, lipopolysaccharides containing most or all of the core oligosaccharides were able to facilitate trimerization.

Bacterial Outer Membrane Proteins↗

PubMed2000

Mutation of the lipopolysaccharide core glycosyltransferase encoded by waaG destabilizes the outer membrane of Escherichia coli by interfering with core phosphorylation.

In Escherichia coli, phosphoryl substituents in the lipopolysaccharide core region are essential for outer membrane stability. Mutation of the core glucosyltransferase encoded by waaG (formerly rfaG) resulted in lipopolysaccharide truncated immediately after the inner core heptose residues, which serve as the sites for phosphorylation. Surprisingly, mutation of waaG also destabilized the outer membrane. Structural analyses of waaG mutant lipopolysaccharide showed that the cause for this phenotype was a decrease in core phosphorylation, an unexpected side effect of the waaG mutation.

Acylation↗

PubMed1966

Genetic determination of enzymes synthesizing O-specific sugars of Salmonella lipopolysaccharides.

Nikaido, Hiroshi (Massachusetts General Hospital, Boston, Mass.), Kishiko Nikaido, and P. Helena Mäkelä. Genetic determination of enzymes synthesizing O-specific sugars of Salmonella lipopolysaccharides. J. Bacteriol. 91:1126-1135. 1966.-Levels of enzymes involved in the biosynthesis of various nucleotide sugars were examined in parental strains and recombinants obtained in crosses between Salmonella of groups B, C(2), and C(1) with the O antigen specificities 4, 5, 12; 6, 8; and 6,7, respectively. The results showed that smooth strains of groups B and C(2) possessed the enzymes for the synthesis of guanosine diphosphate mannose, cytidine diphosphate abequose, and thymidine diphosphate rhamnose; these sugars are constituents of their lipopolysaccharides. Group C(1) lipopolysaccharide is devoid of both abequose and rhamnose, and the corresponding enzymes for cytidine diphosphate abequose synthesis, as well as the enzyme(s) catalyzing the last step(s) of thymidine diphosphate rhamnose synthesis, were undetectable in S. montevideo of this group. Two other enzymes also involved in the biosynthesis of thymidine diphosphate rhamnose were present at a low level of activity; their function in this strain is not known. The analysis of enzyme levels in recombinants indicated that genes determining at least eight of the enzymes involved in the biosynthesis of nucleotide-bound mannose, rhamnose, and abequose were located in the O locus known to determine the specificity of the O antigen. In three rough recombinant strains, enzyme levels indicated that crossing-over had presumably occurred within the O locus. The results also suggested a high degree of nonhomology in this region of the chromosome between groups B and C(1).

Antigens↗

PubMed1968

Quantitative assay of polysaccharide components obtained from cell wall lipopolysaccharides of Xanthomonas species.

The cell wall lipopolysaccharides from 17 species belonging to the genus Xanthomonas were extracted from the cells with hot 45% phenol. After purification, the components of the polysaccharide were obtained by acid hydrolysis of the lipopolysaccharide and were quantitatively assayed. Data obtained show that all preparations contained uronic acid, phosphate, and mannose in molar ratios of approximately 1:2:1, and glucose and rhamnose in more variable concentrations. Most lipopolysaccharides contained either xylose or fucose, but those extracted from X. sinensis and X. campestris contained neither xylose nor fucose.

Cell Wall↗