Measuring interfacial and adhesion forces between bacteria and mineral surfaces with biological force microscopy

Interfacial and adhesion forces between living, unmodified bacterial cells (Escherichia coli) and mineral surfaces (muscovite, goethite, and graphite) have been directly measured in aqueous solution using a force microscope. Native cells are linked to a force-sensing probe that is used to characterize interactions as a mineral surface approaches, makes contact with, and withdraws from bacteria on the probe. Attractive and repulsive interfacial forces were detected at ranges up to 400 nanometers separation, the magnitude and sign depending on the ionic strength of the intervening solution and the mineral surface charge and hydrophobicity. Adhesion forces, up to several nanoNewtons in magnitude and exhibiting various fibrillation dynamics, were also measured and reflect the complex interactions of structural and chemical functionalities on the bacteria and mineral surfaces. Copyright (C) 2000 Elsevier Science Ltd.