Quantification of cell-substratum interactions by atomic force microscopy.

Microorganisms adhere to surfaces and, subsequently, form biofilms. This process is of major interest in biotechnology, environmental sciences and medicine. It is crucial to understand the mechanisms of interactions between substratum and cells or biofilms. By combining force mapping-based atomic force microscopy (AFM) with pyrite-modified cantilevers we quantified the adhesion forces between undenatured planktonic or biofilm cells of Sulfobacillus thermosulfidooxidans and the substratum pyrite with values of 2.6±0.3nN and 77.3±7.1pN, respectively. This was achieved under natural conditions without any artefact resulting from the use of denaturing chemicals such as glutaraldehyde. This new technique is unique for quantifying the real interaction forces between cells or biofilms and their substrata.