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  • 1
    Electronic Resource
    Electronic Resource
    Lipopolysaccharides of polymyxin B-resistant mutants of Escherichia coii are extensively substituted by 2-aminoethyl pyrophosphate and contain aminoarabinose in lipid A (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 16 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Lipopolysaccharides (LPS) of two polymyxin-resistant (pmr) mutants and the corresponding parent strain of Escherichia Coli were chemically analysed for composition and subjected to 31P-NMR (nuclear magnetic resonance) for assessment of phosphate substitution. Whereas the saccharide portions, fatty acids, and phosphate contents were similar in wild-type and pmr LPS, the latter contained two- to threefold higher amounts of 2-aminoethanol. The pmr LPS also contained 4-amino-4-deoxy-l-arabinopyranose (l-Arap4N), which is normally not a component of E. coli LPS. This aminopentose has been assigned to be linked to the 4′-phosphate of lipid A. Comparative 31P-NMR analysis of the de-O-acylated LPS of the wild-type and pmr strains revealed that phosphate groups of the pmr LPS were mainly (71-79%) diphosphate diesters, which accounted for only 20% in the wild-type LPS. Diphosphate monoesters were virtually nonexistent in the pmr LPS, whereas they accounted for 42% of all phosphates in wild-type LPS. In the lipid A of the pmr strains, the 4′-phosphate was to a significant degree (35%) substituted by l-Arap4N, whereas in the wild-type LPS the l-ArapN was absent. In the pmr lipid A1 2-aminoethanol was completely substituting the glycosidic pyrophosphate but not the glycosidic monophosphate, forming a diphosphate diester linkage at this position in 40% of lipid A molecules. In the wild-type LPS the glycosidic position of lipid A carried mostly unsubstituted monophosphate and pyrophosphate. Thus the polymyxin resistance was shown to be associated, along with the esterification of the lipid A 4′-monophosphate by aminoarabinose, with extensive esterification of diphosphates in LPS by 2-aminoethanol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.tb02299.x
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  • 2
    Electronic Resource
    Electronic Resource
    Increased substitution of phosphate groups in lipopolysaccharides and lipid A of the polymyxin-resistant pmrA mutants of Salmonella typhimurium: a 31P-NMR study (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 11 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: De-O-acylated lipopolysaccharides (LPS) of three polymyxin-resistant Salmonella typhimurium pmrA mutants and their parent strains were analysed by 31P-NMR (nuclear magnetic resonance) in order to assess, in relation to polymyxin resistance, the types and degree of substitution of phosphates of the LPS and lipid A. in the pmrA mutant LPS phosphate diesters predominated over phosphate monoesters, whereas the latter were more abundant in the parent wild-type LPS. The increase in the proportion of phosphate diesters was traced to both the core oligosaccharide and the lipld A part. In the latter, the ester-linked phosphate at position 4’was to a large extent (79–88%) substituted with 4-amino-4-deoxy-l-arabinose, whereas in the wild-type LPS the 4′-phosphate was mainly present as monoester. In each LPS, regardless of the pmrA mutation, the glycosidically linked phosphate of lipid A was largely unsubstituted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00329.x
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  • 3
    Electronic Resource
    Electronic Resource
    Eight bacterial proteins, including UDP-N-acetylglucosamine acyltransferase (LpxA) and three other transferases of Escherichia coli, consist of a six-residue periodicity theme (1992)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 97 (1992), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Only a few prokaryotic or eukaryotic enzymes are known to consist of a tandem-repeat structure. This report describes a common hexapeptide-repeat theme in four Escherichia coli transferases and in four less-characterized bacterial proteins. The proteins are the Ssc protein of Salmonella typhimurium (25), UDP-N-acetylglucosamine acyltransferase of E. coli (24), the hypothetical proteins Tms of Bacillus subtilis (23) and Yglm of E. coli (22), succinyldiaminopimelate aminotransferase of E. coli (14), serine acetyltransferase of E. coli (13), NodL of Rhizobium leguminasorum (13), and thiogalactoside acetyltransferase of E. coli (8) (number of repeats indicated in parentheses). In UDP-N-acetylglucosamine acyltransferase, the repeats constitute 55% of the total protein. Each hexapeptide repeat of the eight proteins starts with Ile, Leu, or Val. Position b is occupied by Gly, position d by Gly, Asn, or Asp, and position e by Val or Ala in 52%, 54%, and 56% of the hexapeptide repeats, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1992.tb05471.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of Ssc protein mutations on the outer membrane permeability barrier function in Salmonella typhimurium: a study using ssc mutant alleles made by site-directed mutagenesis (1992)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 90 (1992), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract We have previously discovered and characterized a novel essential enterobacterial protein, the Ssc protein of Salmonella typhimurium and found that the mutation rmVal291→ Met in this protein inhibits bacterial growth at 42°C and the function of its outer membrane permeability barrier at 37°C [7]. In the present paper we prepared, by site-directed mutagenesis, a series of novel plasmid-encoded Ssc mutant proteins and tested their ability to compensate the loss of wild-type Ssc. The mutant proteins Met288→ Lys and Gly289→ Asp completely lacked this ability, and accordingly, were very defective. Ssc mutants Met288→ LeuMet290→ Lys, and Met292→ Lys were partially defective. Mutants Met290→ Leu and Met292→ Leu were non-defective as were also four randomly made mutant proteins with mutations outside the 288–292 region. The S. typhimurium derivative which contained both the chromosomally encoded Ssc Val291→ Met and the plasmid-encoded Ssc Gly289→ Asp had an outer membrane defect more severe than that caused by SscMet291 only. The mutant Ssc proteins had very little, if any, effect on the outer membrane function in the presence of wild-type Ssc. Even though the function of Ssc is not yet known, our results indicate that region 288–292 is important and that SscAsp289 is thus far the most defective mutant Ssc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1992.tb05168.x
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison of the phenotypes of the lpxA and lpxD mutants of Escherichia coli (1995)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 134 (1995), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract We compared the phenotype of two thermosensitive Escherichia coli mutants defective in lipid A biosynthesis i.e. SM101 (lpxA) and CDH23-213 (lpxD). More than 40% of the periplasmic 27-kDa marker enzyme β-lactamase was released from SM101 at 28°C. At this temperature, the mutant still grew with a generation time (67 min), not much longer than that of the parent control strain (57 min). CDH23-213 released β-lactamase only at higher temperatures. SM101 and CDH23-213 were both unable to grow in hypo-osmotic conditions. Derivatives of SM101 and CDH23-213 with mdoA::Tn 10 had identical phenotypes (including thermosensitivity and defective outer membrane permeability barrier to hydrophobic probes) to those of SM101 and CDH23-213, indicating that the potential loss of membrane-derived oligosaccharides (MDO) did not explain these phenotypic properties. A method for the estimation of lipid A synthesis rate was developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1995.tb07942.x
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  • 6
    Electronic Resource
    Electronic Resource
    Lipopolysaccharides of three classes of supersensitive mutants of Salmonella typhimurium (1985)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 30 (1985), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The lipopolysaccharide (LPS) of 3 recently identified antibiotic-supersensitive mutants of Salmonella typhimurium was analyzed and compared to the parent. The amounts of glucose, galactose, heptose, 2-keto-3-deoxyoctonate, total phosphorus, total amino groups, and fatty acids were similar in all of the LPS preparations, and typical of the chemotype Rb2 of the rfaJ parent. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) did not reveal any differences between the mutants and the parent. Ethylenediaminetetraacetic acid and polycations, which partially release LPS from intact cells (presumably by replacing or removing divalent cations between molecules in the outer membrane), liberated similar amounts of [14C]alactose-labelled LPS from the mutants and the parent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1985.tb01107.x
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of ionic strength on polymyxin resistance of pmrA mutants of Salmonella (1981)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 11 (1981), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1981.tb06989.x
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of oligolysines Lys-3, Lys-4, and Lys-5 on the outer membrane permeability of Pseudomonas aeruginosa (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 67 (1990), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A lysine polymer with five residues (Lys-5) was found to remarkably increase the outer membrane (OM) permeability of Pseudomonas aeruginosa to the tested hydrophobic probes (nitrocefin, N-phenyl napthylamine, rifampin). Lys-3 and Lys-4 were inactive. The OM of Escherichia coli and Salmonella typhimurium was not permeabilized by Lys-5. Furthermore, even the action of Lys-5 on the Pseudomonas OM was abolished when the assays were performed in the presence of 150 mM NaCl instead of the low-ionic strength buffer earlier used by investigators studying the effect of polycations on the Pseudomonas OM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1990.tb13828.x
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  • 9
    Electronic Resource
    Electronic Resource
    Does polymyxin B nonapeptide increase outer membrane permeability in antibiotic supersensitive enterobacterial mutants? (1985)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 26 (1985), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The outer-membrane-disorganizing peptide (polymyxin B nonapeptide; PMBN) was able to sensitize even “antibiotic supersensitive” enterobacterial mutants to hydrophobic antibiotics. This resulted in an extreme sensitivity. The mutants included the “deep rough” lipopolysaccharide mutants, as well as the acrA mutant of Escherichia coli and the “class A, B, and C mutants of Salmonella typhimurium. Sensitization factors of approx. 30 or more were found for most antibiotics. Even minimum inhibitory concentrations as low as approx. 0.5 ng/ml (rifampicin), 1.5 ng/ml (erythromycin), 2 ng/ml (fusidic acid), 6 ng/ml (novobiocin), and 30 ng/ml (clindamycin) were achieved in the presence of 30 μg/ml of PMBN. The finding indicates that the mechanisms which mediate the increase in hydrophobic diffusion are different but synergistic in the mutants and in the PMBN-grown cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1985.tb01613.x
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  • 10
    Electronic Resource
    Electronic Resource
    Biological activities of lipopolysaccharides from Pectinatus cerevisiophilus (1984)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 24 (1984), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Lipopolysaccharides (LPS) isolated from four strains of strictly anaerobic beer spoilage bacteria of the species Pectinatus cerevisiophilus were tested for their lethal toxicity in galactosamine-sensitized mice, for their capacity to cause Limulus amebocyte lysate gelation, and for their mitogenic effect for mouse spleen cells. In all of these assays for biological potency, the LPS tested exhibited activities of the same order of magnitude as LPS of Escherichia coli, which was tested for comparison.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1984.tb01240.x
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