title: Permeabilization of biological and artificial membranes by a bacterial dirhamnolipid produced by Pseudomonas aeruginosa.
abstract: Pseudomonas aeruginosa, when cultured under the appropriate conditions, secretes rhamnolipids to the external medium. These glycolipids constitute one of the most interesting classes of biosurfactants so far. A dirhamnolipid fraction was isolated and purified from the crude biosurfactant, and its action on model and biological membranes was studied. Dirhamnolipid induced leakage of internal contents, as measured by the release of carboxyfluorescein, in phosphatidylcholine unilamellar vesicles, at concentrations below its CMC. Membrane solubilization was not observed within this concentration range. The presence of inverted cone-shaped lipids in the membrane, namely lysophosphatidylcholine, accelerated leakage, whereas cone-shaped lipids, like phosphatidylethanolamine, decreased leakage rate. Increasing concentrations of cholesterol protected the membrane against dirhamnolipid-induced leakage, which was totally abolished by the presence of 50 mol% of the sterol. Dirhamnolipid caused hemolysis of human erythrocytes through a lytic mechanism, as shown by the similar rates of K(+) and hemoglobin leakage, and by the absence of effect of osmotic protectants. Scanning electron microscopy showed that the addition of the biosurfactant changed the usual disc shape of erythrocytes into that of spheroechinocytes. The results are discussed within the frame of the biological actions of dirhamnolipid, and the possible future applications of this biosurfactant.
authors.affiliation: Department of Biochemistry and Molecular Biology-A, Faculty of Veterinary, University of Murcia, E-30100 Murcia, Spain.
authors.forename: Marina
authors.initials: M
authors.lastname: Sánchez
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Aranda
authors.forename: José A
authors.initials: JA
authors.lastname: Teruel
authors.forename: María J
authors.initials: MJ
authors.lastname: Espuny
authors.forename: Ana
authors.initials: A
authors.lastname: Marqués
authors.forename: Angeles
authors.initials: A
authors.lastname: Manresa
authors.forename: Antonio
authors.initials: A
authors.lastname: Ortiz
mesh_terms: D002462:Cell Membrane / Q000187:drug effects*; D048430:Cell Shape / Q000187:drug effects; D002784:Cholesterol / Q000737:chemistry; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects; D005452:Fluoresceins / Q000737:chemistry; D006017:Glycolipids / Q000737:chemistry* / Q000494:pharmacology*; D006454:Hemoglobins / Q000378:metabolism; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D008244:Lysophosphatidylcholines; D008567:Membranes, Artificial; D010539:Permeability / Q000187:drug effects; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry; D011092:Polyethylene Glycols / Q000493:pharmacokinetics; D011188:Potassium / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000737:chemistry*; D053835:Unilamellar Liposomes / Q000737:chemistry
chemical_list: D005452:Fluoresceins; D006017:Glycolipids; D006454:Hemoglobins; D008244:Lysophosphatidylcholines; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D053835:Unilamellar Liposomes; C051310:rhamnolipid hemolysin, Pseudomonas aeruginosa; C057561:1-palmitoyl-2-oleoylphosphatidylethanolamine; C006065:We 201; C024098:6-carboxyfluorescein; D011092:Polyethylene Glycols; D002784:Cholesterol; D011188:Potassium; C028694:1-palmitoyl-2-oleoylphosphatidylcholine