Bacterial Adhesion Hydrophobic and Electrostatic Parameters

Van Loosdrecht et al. (1990) have investigated systematically the adhesion of microorganisms to solid surfaces in aquatic environments and describe the initial adhesion process in terms of a colloid-chemical theory. Obviously, bacteria are not inert colloidal particles. Their cell surfaces and their characteristics can change with alterations in environmental conditions. 

Following the arguments by Van Loosdrecht et al. (1990) schematically the interaction between the (negatively charged) cell surface and the solid surface - a sulphated polystyrene surface (hydrophobic, negatively charged) - in presence of polymers, that have adsorbed to both surfaces can be shown to be caused by various interaction energies between the two partially or totally polymer-coated surfaces (Fig. 7.19). The effects of polymers have been interpreted (Van Loosdrecht et al., 1990) as follows  

Ge electrostatic interaction Gfc bridging interaction Gt. total interaction H distance between the two surfaces (From Van Loosdrecht, Norde, Lyklema and Zehnder, 1990) 

Relation between bacterial adhesion to sulphated polystyrene (A) and cell surface characteristics as determined by electrophoretic mobility and contact angle measurement. Results were obtained by interpolating the data points for the adhesion of 17 different strains of bacteria. 

For ii) and iii) loosely structured layers are required, and the chains must protrude into the solution over a distance exceeding the thickness of the electrical double layer so that on approach of the surfaces, the adsorbed layers interfere before the electrical double layers overlap. 

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