Adhesion Strategies of Dictyostelium discoideum - a Force Spectroscopy Study

Biological adhesion is essential for all motile cells and limits locomotion to
substrates displaying a compatible surface chemistry. However, organisms that face
vastly varying environmental challenges require a different strategy. Dictyostelium
discoideum (D.d.), a soil-living slime mould, faces the challenge of overcoming
variable chemistry by employing fundamental forces of colloid science. To understand the
origin of D.d. adhesion, we realized and modified a variety of conditions comprising
specific adhesion proteins,
glycolytic degradation, ionic strength, surface hydrophobicity and van der Waals interactions
by generating tailored model substrates. Employing AFM-based single cell force spectroscopy
we show that experimental force curves upon retraction exhibit two regimes. The
first part up to the critical adhesion force can be described in terms of a continuum model, while
a second regime of the curve beyond the critical adhesion force is governed by stochastic unbinding
of individual binding partners and bond clusters. This versatile mechanism allows D.d. to adhere to a large variety of natural surfaces.