title: Viscous nature of the bond between adhering bacteria and substratum surfaces probed by atomic force microscopy.
abstract: Here we report on the viscous nature of the bond between adhering bacteria and a substratum surface. A tailor-made script was written for an atomic force microscope, that enabled a constant loading force of 1 or 5 nN to act for 30 s upon a bacterium compressed between a cantilever and a glass surface, while measuring its deformation. Time-dependent deformation was fitted to a one element Kelvin-Voigt analogue of the bond to yield a characteristic relaxation time and viscosity of the bond. Viscosities of streptococcal bonds were smaller (<20 kPa s) than those of staphylococcal bonds (>31 kPa s). Since staphylococci are relatively rich in extracellular polymeric substances, it can be inferred that the presence of extracellular polymeric substances yields the major contribution to the viscous response. The viscous nature of the bond between adhering bacteria and substratum surfaces provides the bacteria with more time to respond and protect themselves against external stresses.
authors.affiliation: University of Groningen and University Medical Center Groningen , Department of Biomedical Engineering Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
authors.forename: Yun
authors.initials: Y
authors.lastname: Chen
authors.forename: Henny C
authors.initials: HC
authors.lastname: van der Mei
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Busscher
authors.forename: Willem
authors.initials: W
authors.lastname: Norde
mesh_terms: D001422:Bacterial Adhesion; D018625:Microscopy, Atomic Force; D013211:Staphylococcus aureus / Q000737:chemistry* / Q000166:cytology / Q000502:physiology; D013212:Staphylococcus epidermidis / Q000737:chemistry* / Q000166:cytology / Q000502:physiology; D013499:Surface Properties; D014783:Viscosity