Forces between Minerals and Biological Surfaces in Aqueous Solution

Abstract

At the most fundamental level, intermolecular forces (e.g., van der Waals, electrostatic, solvation, steric) control interactions between biological molecules and mineral surfaces. These are forces with magnitudes of piconewtons to nanonewtons, which operate in a space that is on the order of nanometers. We have used force microscopy to quantitatively probe forces, energies, and distances between crystal surfaces and living microbial cells or biological molecules in their native state. The systems we have studied include those involving: Escherichia coli, Shewanella oneidensis, siderophores, muscovite, goethite, and/or diaspore, in aqueous solutions of varying composition. Direct force measurements at the organic–inorganic interface have been interpreted with theoretical models describing interfacial forces, adhesion, and molecular dynamic calculations. A new perspective on bacterium–mineral interactions is emerging from these studies. We have discovered a world that operates under a very different set of principles than macroscopic bodies. A world where the intermolecular force, rather than gravitational attraction, is the preeminent force controlling the evolution of processes at the bacterium–mineral interface.