title: Influence of exopolysaccharides on the electrophoretic properties of the model cyanobacterium Synechocystis.
abstract: The influence of extracellular polymeric substances (EPS) on cell electrokinetics was investigated in the model cyanobacterium Synechocystis, in wild-type strains and in ten EPS-depleted mutants. The charge density and the softness of the EPS polyelectrolyte layer were calculated from the dependence of the electrophoretic mobility values of the cells with the ionic strength of the surrounding fluid. Electrophoretic mobility data showed that the eleven Synechocystis strains investigated behave as soft particles and cannot be adequately described by classical electrokinetic models of rigid particles. EPS surrounding the cells, especially those released in the growth medium, significantly increased the softness of the cell surface. Furthermore, the anionic nature of EPS resulted in negative surface charge densities, which appeared to be strongly dependent on the composition of the suspending fluid, as documented by a strong reduction of their absolute values in the presence of calcium cations. These finding stresses the importance of the physicochemical properties of EPS and cell surfaces of cyanobacteria, for both cell-to-medium and cell-to-cell communications. In turn, these results emphasize that, whenever possible, natural waters should be used for meaningful ecotoxicological analyses of potential toxics.
authors.affiliation: CEA Saclay, DSM/IRAMIS/SIS2M/LIONS, UMR CEA-CNRS 3299, 91191 Gif sur Yvette, France.
authors.forename: Mariane
authors.initials: M
authors.lastname: Planchon
authors.forename: Thichakorn
authors.initials: T
authors.lastname: Jittawuttipoka
authors.forename: Corinne
authors.initials: C
authors.lastname: Cassier-Chauvat
authors.forename: François
authors.initials: F
authors.lastname: Guyot
authors.forename: Franck
authors.initials: F
authors.lastname: Chauvat
authors.forename: Olivier
authors.initials: O
authors.lastname: Spalla
mesh_terms: D004573:Electrolytes / Q000737:chemistry; D004586:Electrophoresis; D008956:Models, Chemical; D009994:Osmolar Concentration; D010316:Particle Size; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D013499:Surface Properties; D046939:Synechocystis / Q000737:chemistry* / Q000166:cytology
chemical_list: D004573:Electrolytes; D011135:Polysaccharides, Bacterial