Náboj a pevnosť vonkajšej časti bunečnej steny Thiobacillus ferrooxidans

Charge and softness of the outer part of the cell wall of Thiobacillus ferrooxidans in the low ionic strength medium The surface charge and surface potential are parameters influencing the microbial adhesion phenomenon through the electrostatic interaction between bacteria and substrates. The Smoluchowski equation, originally developed for estimating the above parameters from the experimentally accessible electrophoretic mobility of rigid colloid particles, is however inapplicable to the elastic bacterial cells. The problem is that the outer cell wall of bacteria is a layer with a complex polyelectrolyte structure. In this article, the Ohshima ́s model of the “soft” particle is applied to describe the surface electrostatics of Thiobacillus ferrooxidans cells by measuring their electrophoretic mobility in distilled water as a function of a (low) ionic strength and pH. In this model, the rigid core is considered to be covered with a charged ionpenetrable layer of polyelectrolytes. Two model parameters have been determined by the curve fitting at pH from 3.2 to 5.8, namely the number density of the dissociated groups N and the softness parameter 1/λ of the polyelectrolyte layer of the bacterium. A disagreement of the best fit parameters (evaluated by the correlation coefficient) with the analogous parameters determined for other colloids (including bacterial cells) in aqueous solutions of a high ionic strength is discussed.