Molecular composition of the outer membrane of Escherichia coli and the importance of protein-lipopolysaccharide interactions

Gmeiner, Jobst; Schlecht, S

doi:10.1007/bf00428010

Cited by 44 publications

(27 citation statements)

References 36 publications

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“…These gaps may differ in size depending on the amount of outer membrane material released, and they may subsequently be closed at different rates by reintroduction of outer membrane components (LPS, lipids, and proteins) into the gaps. The poor correlation between bacterial protein content and maximum EDTA-induced protein losses might be explained by differences between the bacterial strains investigated with respect to (i) the ratio of "free" LPS and protein-associated LPS in the outer membrane, (ii) the outer membrane protein and LPS content (9), and (iii) the leakage of periplasmic proteins.…”

Section: Resultsmentioning

confidence: 95%

Release of outer membrane fragments from wild-type Escherichia coli and from several E. coli lipopolysaccharide mutants by EDTA and heat shock treatments

1989

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EDTA-induced outer membrane losses from whole cells of wild-type Escherichia coli (O111:B4) and several lipopolysaccharide (LPS) mutants derived from E. coil K-12 D21 were analyzed. EDTA treatment induced losses of LPS (up to 40%), outer membrane proteins OmpA, OmpF/C, and lipoprotein, periplasmic proteins, and phosphatidylethanodamine. The extent of these releases was strain specific. Successively more EDTA was necessary to induce these losses from strains containing LPS with increasing polysaccharide chain length. An additional heat shock immediately following the EDTA treatment had no effect on LPS release, but it decreased the release of outer membrane proteins and reduced the leakage of periplasmic proteins, suggesting that the temporary increase in outer membrane "permeability" caused by Ca +-EDTA treatment was rapidly reversed by the redistribution of outer membrane components, a process which is favored by a mild heat shock. The fact that the material released from E. coli C600 showed a constant ratio of lipoprotein, OmpA, and phosphatidylethanolamine at all EDTA concentrations tested suggests that the material is lost as specific outer membrane patches. The envelope alterations caused by EDTA did not result in cell lysis.Gram-negative bacteria survive in hostile environments largely because they are enveloped by the outer membrane (33). The outer membrane is characterized by several wellstudied major structural proteins, a limited number of minor proteins, and the presence of lipopolysaccharide (LPS), a unique class of macromolecules restricted to the outer leaflet of the outer membrane of gram-negative bacteria (24, 30). LPSs contain three distinct parts: lipid A, which anchors the molecule in the outer leaflet of the outer membrane (20, 28); the sugar "core" unit; and the 0-antigen chain, which protrudes into the surroundings of the bacterium (20,24). The inner leaflet of the outer membrane is mainly formed by phosphatidylethanolamine (PE) and, to a small extent, by the fatty acid residues of lipoprotein, which connects the outer membrane to the underlaying peptidoglycan layer (4,12,25,39).LPS-associated cations are believed to stabilize the outer membrane through salt bridges and neutralization of the repulsive forces of neighboring LPS molecules and/or proteins, leading to a tightly cross-linked LPS layer (8,26,34).EDTA chelates divalent cations, thus offsetting their stabilizing effects. EDTA treatment results in losses of LPS (30 to 50%) and minor amounts of proteins and phospholipids (16,19), and it increases the permeability of the outer membrane of gram-negative bacteria (17). Consequently, EDTA is often used in procedures to translocate macromolecules into the bacterium. Such methods are generally very strain specific, and their success depends on growth conditions and growth stage (2, 13), presumably due to alterations in the cell envelope that occur in stationary-phase cells. An undesirable side effect of some of these treatments is that they may lead to decreased cell viability, followed by...

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Section: Resultsmentioning

confidence: 95%

Release of outer membrane fragments from wild-type Escherichia coli and from several E. coli lipopolysaccharide mutants by EDTA and heat shock treatments

1989

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“…Nevertheless, the degree of aerobactin binding was similar in the clinical isolate D551 and in BZB1022(pABNl), indicating comparable expression of the IutA protein. Thus, either the aerobactin receptor in D551 lacks immunological homology with that encoded by ColV-K30 in the immunizing strain, or it is masked by structures such as LPS which covers about 45 % of the surface area of Gram-negative bacteria (Gmeiner & Schlect, 1980). While small molecules such as aerobactin (molecular mass 536) would not be significantly inhibited from gaining access to receptors in the outer membrane by LPS, it is likely that large proteins such as cloacin DF13 or immunoglobulin (with molecular masses of 70000 and greater) or phage-adsorption structures would be sterically excluded from the bacterial surface by LPS.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of Biological Activities of the Aerobactin Receptor Protein in Rough Strains of Escherichia coli by Polyclonal Antiserum Raised against Native Protein

Roberts

Wooldridge²,

Gavine³

et al. 1989

Microbiology

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The aerobactin iron-uptake system of plasmid ColV-K30, genetically isolated from other plasmid determinants by molecular cloning, was sufficient to restore full virulence in a mouse peritonitis model to a clinical Escherichia coli isolate, D551 (078 : H-), whose resident aerobactin-encoding ColV plasmid had been lost by curing. Antiserum was raised in rabbits against live E. coli K 12 cells expressing the outer-membrane aerobactin receptor protein and absorbed with an isogenic strain lacking the receptor. This antiserum inhibited binding of aerobactin, cloacin DF13 and bacteriophage B74K to the native protein in whole E. coli K12 bacteria expressing the receptor, or in membranes prepared from such organisms. However, it did not react with the native receptor protein in several wild strains unless lipopolysaccharide was first removed by treatment with trichloroacetic acid, nor did it protect mice in experimental infections with strain D55 1. Antisera raised in rabbits against partially or fully denatured forms of the aerobactin receptor reacted only in assays involving denatured protein; they showed no inhibition of the biological activities of the native receptor.

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“…Escherichia coli D21g is gram-negative, nonmotile bacterial strain that produces minimal amounts of lipopolysaccharides (LPS) (Gmeiner and Schlecht, 1980;Walker et al, 2004) and extra-cellular polymeric substances (EPS) (Razatos et al, 1998). The effective diameter of D21g is 1.84 μm .…”

Section: Methodsmentioning

confidence: 99%

Causes and implications of colloid and microorganism retention hysteresis

Bradford

Kim

2012

Journal of Contaminant Hydrology

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Molecular composition of the outer membrane of Escherichia coli and the importance of protein-lipopolysaccharide interactions

Cited by 44 publications

References 36 publications

Release of outer membrane fragments from wild-type Escherichia coli and from several E. coli lipopolysaccharide mutants by EDTA and heat shock treatments

Release of outer membrane fragments from wild-type Escherichia coli and from several E. coli lipopolysaccharide mutants by EDTA and heat shock treatments

Inhibition of Biological Activities of the Aerobactin Receptor Protein in Rough Strains of Escherichia coli by Polyclonal Antiserum Raised against Native Protein

Causes and implications of colloid and microorganism retention hysteresis

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