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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutants of Escherichia coli K12, defective in phosphatidylserine synthetase (pss), can be isolated as temperature-sensitive, conditional lethals. When cultivated at intermediate temperatures (30 degrees), such mutants contain approximately 3 times more phosphatidylglycerol plus cardiolipin (and less phosphatidylethanolamine) than normal. We now wish to report that, under these conditions, the pss-8 mutant is hypersensitive to certain antibiotics, especially to streptomycin, kanamycin, and gentamicin, although also to ampicillin and novobiocin. At 30 degrees, the membrane protein and fatty acid composition of pss-8 is nearly normal, i.e. identical with an isogenic pss+ organism. Radiochemical labeling and bacteriophage growth studies show that lipopolysaccharide is also unaltered. Therefore, the antibiotic hypersensitivity of pss-8 differs from previously reported hypersensitivities, associated with lipopolysaccharide defects. These results suggest that the polar phospholipid headgroups may play an important role in maintaining the barrier function of the outer gramnegative membrane and that putative inhibitors of the phosphatidylserine synthetase might potentiate the action of numerous antibiotics currently in clinical use.
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PMID:Envelope composition and antibiotic hypersensitivity of Escherichia coli mutants defective in phosphatidylserine synthetase. 19 63

Protein II, a major outer cell envelope membrane protein, was found together with lipopolysaccharide to stoichiometrically inhibit conjugation in Escherichia coli K12.
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PMID:Action of a major outer cell envelope membrane protein in conjugation of Escherichia coli K-12. 32 38

Phospholipids in whole cells of wild type Escherichia coli K12 are not degraded by exogenous phospholipases, whereas those of isolated outer membranes are completely degraded. It is concluded that the resistance of phospholipids in whole cells is due to shielding by one or more other outer membrane components. The nature of the shielding component(s) was investigated by testing the sensitivity of whole cells of a number of outer membrane mutants. Mutants lacking both major outer membrane proteins b and d or the heptose-bound glucose of their lipopolysaccharide, are sensitive to exogenous exogenous phospholipases. Moreover, cells of a mutant which lacks protein d can be sensitized by pretreatment of the cells with EDTA. From these results and from data on the chemical composition of the outer membranes, it is concluded that proteins b and d, the heptose-bound glucose of lipopolysaccharide and divalent cations are responsible for the inaccessibility of phospholipids to to exogenous phospholipases.
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PMID:Architecture of the outer membrane of Escherichia coli K12. I. Action of phospholipases A2 and C on wild type strains and outer membrane mutants. 32 15

The authors carried out a comparative study of the genetically connected Sh. flexneri cultures (3 virulent strains, 3 clones of an avirulent mutant selected in the flux of an oblique light from the virulent strain, and lac+ Kcp A-hybrids obtained by crossing the initial virulent cultures with the E. coli K12 Hfr strains). The absence of any correlation between the virulence of the strains under study and the lipopolysaccharide (by rhamnose) content in the extracts from them in growing the cultures in the presence of calcium ions was noted. Toxicity of the extracts from the virulent cultures was demonstrated on a model of developing chick embryos. No such property was possessed by the extracts from avirulent strains. The extracts from the virulent cultures in nontoxic doses possessed the capacity to decrease LD50 of shigella strains used for the infection. The biologically active factor determined in the extracts from the virulent cultures apparently was not lipopolysaccharide.
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PMID:[Biological activity of extracts isolated from a virulent strain of Sh. flexneri grown in the presence of calcium ions]. 32 61

The rfa-7 lipopolysaccharide core mutation carried by the R mutant F680, derived from Shigella flexneri F6S serotype 5b, has been mapped by conjugation and transduction experiments. The results show a chromosomal distance of about 1 min between rfa-7 and mtl. Such a position would be similar to those of rfa genes in Escherichia coli K12 and Salmonella typhi-murium LT2. Conjugational transfer of E. coli K12 rfa+ genes to mutant F680 restored S. flexneri O-specificity. Chemical analyses performed on the lipopolysaccharide of such a rfa+ hybrid suggest that this strain can attach the S. flexneri serotype 5b O-specific polysaccharide to the E. coli K12 core.
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PMID:[Study of a "RFA" locus coding for cell wall lipopolysaccharide core biosynthesis in "Shigella flexneri" F6S (author's transl)]. 32 20

A series of mutants of Escherichia coli K12 resistant to lipopolysaccharide (LPS)-specific bacteriophages were isolated, and examined with regard to their general properties, phage typing, chemical analysis of their LPS, and genetic analysis. Fourteen classes of mutants were distinguished on the basis of phage typing and sensitivity to bile salts. Three of the mutant classes are sensitive to phages to which the parent is resistant. Mutants which are sensitive to bile salts generally lack heptose in their LPS, but two mutant classes are exceptions to this rule. Analyses of the sugars in the purified LPS of all mutant classes indicated that mutants were obtained which are blocked at most stages in core polysaccharide synthesis. On the basis of the chemical analysis, in conjunction with phage typing data and other known properties of the mutants, it is deduced which residue(s) is involved as a receptor for each of the phages used and which residues hinder these receptors. Some of the mutant classes do not seem to be changed in their LPS structure. Many of the mutations map in or near the rfa locus, but some are far removed from this region.
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PMID:Bacteriophage-resistant mutants of Escherichia coli K12. Location of receptors within the lipopolysaccharide. 33 45

Three classes of mutants of Escherichia coli K12, isolated by selection for resistance to lipopolysaccharide-specific bacteriophages, were agglutinated by Concanavalin A which is presumed to interact with the lipopolysaccharide component of the outer membrane. Wheat germ and soy bean agglutinins did not agglutinate the parent or mutant strains. The adsorption of certain bacteriophages was also inhibited by Concanavalin A. The pattern of inhibition of adsorption of bacteriophages suggests that non-specific masking of receptors may occur, as well as specific masking of terminal glucose residues. Although bacteria were agglutinated by Concanavalin A, the permeability of the outer membrane seemed unaffected.
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PMID:Bacteriophage-resistant mutants of Escherichia coli K12 with altered lipopolysaccharide. Studies with concanavalin A. 33 46

Thermosensitive mutants of Escherichia coli K12 were grown at 30 degrees C and 40 degrees C. The serologic properties and the composition of their lipopolysaccharides were investigated. The inhibition of hemagglutination by the lipopolysaccharides of various mutant strains was tested against the anti-E. coli K12 CR34 system. An inhibition was observed with all the mutants but one, CR34 T83 which had no inhibitory effect. Chemical analysis of lipopolysaccharides and mass spectrometric analysis of their methylated derivatives indicated the presence of the same components in the various lipopolysaccharides: glucose, galactopyranose, galactofuranose, heptopyranose and heptofuranose. However the 2,3,4 tri-O-methyl glucose is missing in the lipopolysaccharide of the mutant T83. This result agrees with the absence of a substituent on the 6-position of the non-reducing core-terminal glucose. The lipopolysaccharide of the T83 mutant has the complete core-type of E. coli K12. The relations of mutations with modifications of the composition of inner and outer envelopes in various mutants are discussed.
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PMID:[Lipopolysaccharides from thermosensitive mutants of Escherichia coli K12 (author's transl)]. 33

A method of identifying plasmids containing genes responsible for synthesis of nucleotide sugar:lipopolysaccharide glycosyltransferases is described. Hybrid ColE1 plasmids containing random fragments of the chromosome of Escherichia coli K12 were introduced into an indicator strain of Salmonella typhimurium which lacks UDP-glucose:lipopolysaccharide glucosyltransferase I due to an rfaG mutation. Plasmids capable of correcting the transferase defect were identified by their ability to convert the bacteriophage sensitivity pattern of the recipient strain from Ffm-sensitive to Ffm-resistant. Analysis of the lipopolysaccharide of the S. typhimurium/ColE1 hybrid strains and assay of cell extracts defined the new enzyme activities. Two plasmids were identified which carried the rfaG+ gene; one of these plasmids also contained genetic information for a second glucosyltransferase, the E. coli glucosyltransferase II, which normally is not present in S. typhimurium.
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PMID:Cloning of genes for bacterial glycosyltransferases. I. Selection of hybrid plasmids carrying genes for two glucosyltransferases. 36 61

A hybrid ColE1 plasmid containing DNA from Escherichia coli K12 were identified which was capable of correcting the defect in UDP-galactose:lipopolysaccharide alpha1,3-galactosyltransferase in an rfaH mutant of Salmonella typhimurium. Expression of the gene for this enzyme was also demonstrated in several strains of E. coli by direct assay. The E. coli and S. typhimurium enzymes are similar in catalytic properties and immunologic specificity. The finding of the galactosyltransferase activity in E. coli extracts is surprising since the alpha1,3-galactosylglucose disaccharide which is the product of the enzyme-catalyzed reaction does not appear to be present in the E. coli lipopolysaccharide.
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PMID:Cloning of genes for bacterial glycosyltransferases. II. Selection of a hybrid plasmid carrying the rfah gene. 36 62


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