title: Relations between hydrophobicity tested by three methods and surface chemical composition of Escherichia coli.
abstract: The cell surface hydrophobicity of three strains of Escherichia coli cultured in liquid medium and on solid medium was measured using various methods including adsorption to pxylene, partition of cells in a polyethylene glycol/dextran (PEG/DEX) two phase system and contact angle measurements. The percentage adsorbed to pxylene ranged from 1.6% to 67% and the percentage of cells in polyethylene glycol phase ranged from 19% to 64%. The contact angle data of less than 40 degrees C revealed a hydrophylic character of the E. coli strains studied here. No relations were found between paraxylene/water partitioning, PEG/DEX partioning and water contact angles. The linear correlation coefficients between the results of the three hydrophobicity assays and the elemental concentration ratios obtained by X-ray photoelectron spectroscopy (XPS) were calculated. A linear correlation was found between the contact angles and the O/C ratios (r=0.91) and the N/C ratios (0.67). The adsorption to pxylene correlates better with N/C ratios (0.88) but does not correlate with O/C ratios (0.46). However, this test correlates with N/P ratios (0.79). No relation was obtained between partition in PEG/DEX system and any elemental concentration ratios. The surface composition determined by XPS was converted into a molecular composition in terms of proteins, polysaccharides, and hydrocarbon-like compounds. The proteins/polysaccharides and the hydrocarbons/polysaccharides seems to determine the contact angle of E. coli but not the adsorption to paraxylene or partition in the PEG/DEX system.
authors.affiliation: Laboratoire de valorisation et séurité des produits alimentaires, Faculté des sciences et techniques, Beni mellal, Maroc.
authors.forename: H
authors.initials: H
authors.lastname: Latrache
authors.forename: Ghmari A
authors.initials: GA
authors.lastname: El
authors.forename: M
authors.initials: M
authors.lastname: Karroua
authors.forename: A
authors.initials: A
authors.lastname: Hakkou
authors.forename: Mousse H
authors.initials: MH
authors.lastname: Ait
authors.forename: Bouadili A
authors.initials: BA
authors.lastname: El
authors.forename: P
authors.initials: P
authors.lastname: Bourlioux
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003911:Dextrans / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D011092:Polyethylene Glycols / Q000737:chemistry; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D013499:Surface Properties; D013500:Surface Tension
chemical_list: D003911:Dextrans; D011092:Polyethylene Glycols