Bacterial spore interactions with planar surfaces in aquatic environments, including adhesive forces and force–distance profiles, are influenced by the geometry and physicochemical properties of the system. The characteristics of spores of Bacillus thuringiensis (Bt) are determined using electron microscopy and electrokinetic measurements. The average size of the spores is 1.57 μm long and 0.86 μm wide, and the zeta potential values are negative for the solutions used in this work. The zeta potentials of the spores and mica surfaces used in the experiments are measured as a function of pH and ionic strength. The Derjaguin, Landau, Verwey and Overbeek (DLVO) theory is employed to predict the interaction force between the spores and planar surfaces as a function of the separation distance, and a force balance is used to explain the adhesive force. Theoretical estimations are compared to experimental …