Initial adhesion of Bacillus subtilis on soil minerals as related to their surface properties

The initial adhesion of micro-organisms on solid surfaces strongly affects their transport and fate in soil and aquatic environments. Experiments on Bacillus subtilis with various soil minerals (including kaolinite, montmorillonite, goethite, birnessite, quartz and mica) were conducted to determine the role of surface properties in adhesion and to test the validity of the extended Derjaguin, Landau, Verwey and Overbeek (DLVO) theory for bacterial adhesion. Adhesion of B. subtilis on all six minerals conformed to the Langmuir equation. Adhesion capacity and affinity showed a significant correlation with the specific external surface area (SESA) of the minerals and the calculated electrostatic energy barrier, respectively, but no significant correlation was observed between hydrophobicity and the adhesion parameters. These results demonstrate that adhesion capacity and affinity are primarily controlled by the SESA of the minerals and the surface electrical properties, respectively. The dependence of the adhesion capacity on SESA may be explained by the cellmineral interaction model. Adhesion could be well predicted by the extended DLVO theory. The initial adhesion of bacteria with soil minerals can be evaluated by using independently measured surface properties of these components based on the extended DLVO theory combined with the Langmuir equation.