Surface physicochemical properties of Pseudomonas fluorescens and impact on adhesion and transport through porous media

The physiological state of an examined Pseudomonas fluorescens strain had a significant impact on its adhesion to glass surfaces and transport through glass-bead columns. In both batch and column studies collision efficiencies, a, for exponential phase cells were much larger (alpha approximate to 2-3) than for stationary or decay phase cells (alpha approximate to 0.5-0.7). Centrifugation of exponential phase cells substantially reduced collision efficiencies (alpha approximate to 0.8). Over the examined range (0.02-0.2 M), ionic strength had no impact on cell attachment. The Lewis acid/base (A/B) character of the cell surface varied with physiological states: exponential phase cells exhibited larger values of the electron-donor parameter of the polar surface tension component, gamma(s)(-), than stationary or decay phase cells, resulting in larger calculated cell hydrophilicities. A reduction in exponential phase cell zeta-potential was observed upon centrifugation. Traditional Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy profiles (between cells and glass surfaces) indicated energy maxima of the order of 90-130kT, and secondary energy minima of less than 10kT. Extended DLVO modeling predicted infinite energy barriers attributable to repulsive A/B interactions, and similar magnitude secondary energy minima. A pseudo-chemical kinetic approach was used to calculate activation energies of adhesion from experimental collision efficiencies. Collision efficiencies were also predicted from a diffusion-governed mass transport model incorporating interacting force fields. Predicted energy barriers underestimated cell collision efficiencies, suggesting that secondary energy minimum interactions governed initial attachment of cells. The partial reversibility of adhesion upon ionic strength reduction supported the secondary minimum interaction hypothesis. (C) 1999 Elsevier Science B.V. All rights reserved.