Presence of exposed phospholipids in the outer membrane of Vibrio cholerae

Paul, Saptarshi; Chaudhuri, Keya; Chatterjee, Anadi N.; Das, Jyotirmoy

doi:10.1099/00221287-138-4-755

Cited by 26 publications

(27 citation statements)

References 25 publications

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“…The generally high susceptibility of N. gonorrhoeae to lipophilic agents may be consistent with the presence of a mixed LPS-phospholipid leaflet in the OM, but phospholipase C digestion of intact cells suggested that the outer leaflet did not contain much phospholipid (391). In contrast, the presence of phospholipids on the outer surface of OM was detected by using a macromolecular labeling reagent with V. cholerae (486), and a similar situation may be found with some other gram-negative bacteria.…”

Section: The Lipid Bilayer As a Diffusion Barrier The Asymmetric Bilayermentioning

confidence: 91%

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

Nikaido

2003

Microbiol Mol Biol Rev

3,801

3,800

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Gram-negative bacteria characteristically are surrounded by an additional membrane layer, the outer membrane. Although outer membrane components often play important roles in the interaction of symbiotic or pathogenic bacteria with their host organisms, the major role of this membrane must usually be to serve as a permeability barrier to prevent the entry of noxious compounds and at the same time to allow the influx of nutrient molecules. This review summarizes the development in the field since our previous review (H. Nikaido and M. Vaara, Microbiol. Rev. 49:1-32, 1985) was published. With the discovery of protein channels, structural knowledge enables us to understand in molecular detail how porins, specific channels, TonB-linked receptors, and other proteins function. We are now beginning to see how the export of large proteins occurs across the outer membrane. With our knowledge of the lipopolysaccharide-phospholipid asymmetric bilayer of the outer membrane, we are finally beginning to understand how this bilayer can retard the entry of lipophilic compounds, owing to our increasing knowledge about the chemistry of lipopolysaccharide from diverse organisms and the way in which lipopolysaccharide structure is modified by environmental conditions

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Section: The Lipid Bilayer As a Diffusion Barrier The Asymmetric Bilayermentioning

confidence: 91%

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

Nikaido

2003

Microbiol Mol Biol Rev

3,801

3,800

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“…V. cholerae is extremely sensitive to a wide variety of compounds, particularly hydrophobic and amphipathic agents (21). It is about 100 times more sensitive than E. coli to novobiocin, a hydrophobic antibiotic that has been used as an indicator of bacterial OM permeability to hydrophobic compounds (Table 1).…”

Section: Resultsmentioning

confidence: 99%

“…V. cholerae cells grown to the logarithmic phase in the presence or absence of bile were dansylated following the method of Paul et al (21). Briefly, dansyl chloride-cyclodextrin complex was added to cells suspended in 1 mM MgCl 2 -50 mM borate buffer (pH 8.5) and stirred in darkness for 60 min at room temperature.…”

Section: Methodsmentioning

confidence: 99%

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Effect of Bile on the Cell Surface Permeability Barrier and Efflux System of Vibrio cholerae

et al. 2004

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Gram-negative bacteria are inherently impermeable to hydrophobic compounds, due to the synergistic activity of the permeability barrier imposed by the outer membrane and energy dependent efflux systems. The gram-negative, enteric pathogen Vibrio cholerae appears to be deficient in both these activities; the outer membrane is not an effective barrier to hydrophobic permeants, presumably due to the presence of exposed phospholipids on the outer leaflet of the outer membrane, and efflux systems are at best only partially active. When V. cholerae was grown in the presence of bile, entry of hydrophobic compounds into the cells was significantly reduced. No difference was detected in the extent of exposed phospholipids on the outer leaflet of the outer membrane between cells grown in the presence or absence of bile. However, in the presence of energy uncouplers, uptake of hydrophobic probes was comparable between cells grown in the presence or absence of bile, indicating that energy-dependent efflux processes may be involved in restricting the entry of hydrophobic permeants into bile grown cells. Indeed, an efflux system(s) is essential for survival of V. cholerae in the presence of bile. Expression of acrAB, encoding an RND family efflux pump, was significantly increased in V. cholerae cells grown in vitro in the presence of bile and also in cells grown in rabbit intestine.Vibrio cholerae, a noninvasive enteric bacterium, is the causative agent of the diarrheal disease cholera. Cholera remains a major cause of human mortality in developing countries, where conditions of poor sanitation, war, famine, and malnourishment contribute to regular episodes of cholera epidemics. For successful infection of its human host, V. cholerae must colonize the small intestine and produce copious amounts of cholera toxin (CT), a potent enterotoxin that causes the massive fluid loss characteristic of the disease. In addition to obvious virulence factors like CT, other toxins, toxin-coregulated pilus, hemolysins, and hemagglutinins (factors essential for survival of the bacteria in vivo and evasion of the host defense system) also contribute to the pathogenecity of V. cholerae (for a review, see references 12 and 24).Enteric pathogens and normal intestinal flora must necessarily survive and colonize the intestine in the presence of bile. Bile salts are surface-active, amphipathic compounds with pronounced detergent-like activity that can cause disaggregation of the lipid bilayer structure of cellular membranes (11). However, gram-negative enteric bacteria are inherently resistant to bile, partly due to the basic, asymmetric structure of their outer membranes (OMs). Although the inner surface of the OM contains phospholipids, a characteristic lipopolysaccharide (LPS) is present on the outer leaflet that significantly retards diffusion of hydrophobic compounds across the OM. The OM thus functions as an effective permeability barrier and gives protection to enteric bacteria from potentially noxious agents present in the intestine, particula...

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“…3C), may be because of the increased curvature of the released blebs in comparison with that of the intact outer membrane, promoting migration of PL that normally reside within the inner leaflet of the outer membrane (33). However, the extreme lipid asymmetry observed in the outer membrane of E. coli and Salmonella typhimurium may not be representative of all Gram-negative bacteria (43).…”

Section: Discussionmentioning

confidence: 99%

Biochemical and Functional Characterization of Membrane Blebs Purified from Neisseria meningitidis Serogroup B

Post

Zhang

Eastvold

et al. 2005

Journal of Biological Chemistry

119

137

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Studies with purified aggregates of endotoxin have revealed the importance of lipopolysaccharide-binding protein (LBP)-dependent extraction and transfer of individual endotoxin molecules to CD14 in Toll-like receptor 4 (TLR4)-dependent cell activation. Endotoxin is normally embedded in the outer membrane of intact Gram-negative bacteria and shed membrane vesicles ("blebs"). However, the ability of LBP and CD14 to efficiently promote TLR4-dependent cell activation by membrane-associated endotoxin has not been studied extensively. In this study, we used an acetate auxotroph of Neisseria meningitidis serogroup B to facilitate metabolic labeling of bacterial endotoxin and compared interactions of purified endotoxin aggregates and of membrane-associated endotoxin with LBP, CD14, and endotoxin-responsive cells. The endotoxin, phospholipid, and protein composition of the recovered blebs indicate that the blebs derive from the bacterial outer membrane. Proteomic analysis revealed an unusual enrichment in highly cationic (pI > 9) proteins. Both purified endotoxin aggregates and blebs activate monocytes and endothelial cells in a LBP-, CD14-, and TLR4/MD-2-dependent fashion, but the blebs were 3-10-fold less potent when normalized for the amount of endotoxin added. Differences in potency correlated with differences in efficiency of LBPdependent delivery to and extraction of endotoxin by CD14. Both membrane phospholipids and endotoxin are extracted by LBP/soluble CD14 (sCD14) treatment, but only endotoxin⅐sCD14 reacts with MD-2 and activates cells. These findings indicate that the proinflammatory potency of endotoxin may be regulated not only by the intrinsic structural properties of endotoxin but also by its association with neighboring molecules in the outer membrane.

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Presence of exposed phospholipids in the outer membrane of Vibrio cholerae

Cited by 26 publications

References 25 publications

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

Effect of Bile on the Cell Surface Permeability Barrier and Efflux System of Vibrio cholerae

Biochemical and Functional Characterization of Membrane Blebs Purified from Neisseria meningitidis Serogroup B

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