Microbial Cells Force Spectroscopy by Atomic Force Microscopy: A Review.

Bacterial adhesion and biofilm formation are important phenomena which can produce both detrimental and beneficial effects in several fields. Research is thus focused on the modulation of the properties of material surfaces in order to design and develop substrates able to control bacterial adhesion process, which is the first trigger event of biofilm formation. Several theoretical predictions and experimental procedures have been developed to investigate the physical, chemical and biological mechanisms regulating the attachment of bacteria to solid substrates. Nevertheless, a comprehensive understanding has not been achieved yet, limiting the capability of individuating effective technological strategies to achieve the desired bacterial adhesion behavior. The development of new experimental procedures able to furnish deeper information about bacterial adhesion mechanism is thus needed. Microbial cell force spectroscopy (MCFS) is an atomic force microscopy (AFM) based technique, consisting in the detection of force-distance curves using particular probes obtained immobilizing bacterial cells at the free end of a flexible microcantilever, which allows the detection of the different kinds of cell-surface interaction forces. In this work, we review the state of the art in the development of MCFS, focusing on its working principle and applications. A brief description of the current models and conventional experimental procedures used to evaluate bacterial adhesion to surfaces is reported. Then, the instrumentation and the working principle, the current procedures used to prepare bacterial cells probes and the main applications of the technique are described with the aim of pointing out the advantages of the technique and the limits which still have to be overcome.