title: Deciphering the aggregation mechanism of bacteria (Shewanella oneidensis MR1) in the presence of polyethyleneimine: Effects of the exopolymeric superstructure and polymer molecular weight.
abstract: Aggregation tests between bacteria and Polyethyleneimine (PEI) of low (600g/mol) and high (750,000g/mol) molecular weight were performed in order to address the physico-chemical mechanisms underlying the interactions between cationic polymer and bacterial membranes. The selected strain, Schewanella oneidensis MR-1, produces a lipopolysaccharide (LPS) of various lengths depending on the growth conditions. Optical density, bioaggregate size, electrophoretic mobility measurements, TEM and AFM observations, and cell lysis tests (crystal violet release), were collected to describe the PEI-mediated aggregation of LPS-O-antigen-free and LPS-O-antigen-decorated bacteria. The results show that PEI of low molecular weight (600g/mol) fails to aggregate bacteria, whereas PEIs of higher molecular weight (60,000 and 750,000g/mol) lead to flocculation at low polymer concentrations. In addition, the LPS-O antigen bacterial superstructure is shown to act as a protective barrier, thus delaying the harmful effects of the cationic polymer. Despite this protection, the interaction of bacterial membranes with increasing concentrations of PEI leads to a series of deleterious processes including biosurface modification (peeling, membrane permeabilization and/or lysis), aggregation of bacterial cells, and complexation of PEI with both released biosurface fragments and cytoplasmic residues issued from lysis.
authors.affiliation: CNRS, LIEC (Laboratoire Interdisciplinaire des Environnements Continentaux), UMR7360, Vandoeuvre-lès-Nancy F-54501, France; Université de Lorraine, LIEC (Laboratoire Interdisciplinaire des Environnements Continentaux), UMR7360, Vandoeuvre-lès-Nancy F-54501, France. Electronic address: marieevekrapf@gmail.com.
authors.forename: Marie-Eve M
authors.initials: ME
authors.lastname: Krapf
authors.affiliation: Université de Lorraine, LIEC (Laboratoire Interdisciplinaire des Environnements Continentaux), UMR7360, Vandoeuvre-lès-Nancy F-54501, France. Electronic address: bruno.lartiges@get.obs-mip.fr.
authors.forename: Bruno
authors.initials: B
authors.lastname: Lartiges
authors.affiliation: University of Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, CNRS UMR7564, 405 rue de Vandoeuvre, F-54600 Villers-lès-Nancy, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Merlin
authors.affiliation: University of Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, CNRS UMR7564, 405 rue de Vandoeuvre, F-54600 Villers-lès-Nancy, France.
authors.forename: Grégory
authors.initials: G
authors.lastname: Francius
authors.affiliation: University of Lorraine, Laboratoire de Microscopie Electronique, Université Henri-Poincaré (Nancy I), BP 239, 54506 Vandoeuvre-les-Nancy Cedex, France.
authors.forename: Jaafar
authors.initials: J
authors.lastname: Ghanbaja
authors.affiliation: CNRS, LIEC (Laboratoire Interdisciplinaire des Environnements Continentaux), UMR7360, Vandoeuvre-lès-Nancy F-54501, France.
authors.forename: Jérôme F L
authors.initials: JF
authors.lastname: Duval
mesh_terms: D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects* / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D005427:Flocculation / Q000187:drug effects; D008070:Lipopolysaccharides / Q000096:biosynthesis / Q000378:metabolism; D008970:Molecular Weight; D011094:Polyethyleneimine / Q000737:chemistry / Q000494:pharmacology*; D020592:Shewanella / Q000737:chemistry / Q000187:drug effects* / Q000648:ultrastructure; D013329:Structure-Activity Relationship
chemical_list: D008070:Lipopolysaccharides; D011094:Polyethyleneimine
keywords: Aggregation; Flocculation; Lipopolysaccharide; Polyethyleneimine; Shewanella oneidensis MR-1