Effects of Solution Chemistry on Bacterial Adhesion with Phyllosilicates and Goethite Explained by the Extended DLVO Theory.

Adhesion ofBacillus subtilison kaolinite, montmorillonite, and goethite was investigated over a wide range of ionic strength (IS) and pH using batch experiment. The related surface properties (size, zeta potential, and hydrophobicity) under varying conditions were systematically determined and the interaction energy between the cell and minerals were calculated using the extended Derjaguin, Landau, Verwey, and Overbeek (ExDLVO) theory. Adhesion on kaolinite and montmorillonite increased with IS at low level (< 0.01 mol L−1MgCl2) but declined at high IS level. An increase in IS generally depressed bacterial adhesion on goethite. Elevated pH resulted in decreasing the adhesions on all three minerals. The IS- and pH-effects on adhesion forphyllosilicatesystems followed the ExDLVO predictions. For goethite systems, this theory predicted the adhesion trend with IS and that under basic pH, but failed to explain the adhesion at low pH. Such deviation from the theory possibly resulted from chemical interactions between extracellular polymeric substances on cell surface and goethite. These results imply that bacterial adhesions onphyllosilicates are primarily governed by the ExDLVO interactions, and those on iron oxides are mediated by the combination of ExDLVO and non-ExDLVO interactions. [ABSTRACT FROM PUBLISHER]