Histogram of total rupture forces (left) and work of detachment (right) between a mannose coated AFM cantilever and an <i>A. castellanii</i> trophozoite after 0.5 s, 5 s and 10 s contact time, respectively.

<p>Adhesion forces and work of detachment increase with time. Comparably high forces between 0.5 nN and 30 nN were measured.</p

Single rupture analysis of the last rupture event between a mannose-coated AFM cantilever and an <i>A. castellanii</i> cell after 0.5 s, 5 s and 10 s contact time.

<p>Histograms (left) and boxplots (right) of rupture forces (top), slopes (center) and tether lenghts (bottom) of the last rupture event. Significant changes in rupture forces were observed between 0 s and 5 s (*, p≤0.05), and 0 s and 10 s (***, p≤0.001) contact time. The slopes were not significantly changed by the duration of cantilever-amoeba contact. All measured slopes were above -100 pN/s. Significant changes of tether lengths were only recorded between 0 s and 10 s contact time (***, p≤0.001).</p

2D probability density plots of slopes versus position of the last rupture event when breaking the contact between a mannose coated AFM cantilever and a <i>A. castellanii</i> cell after 0.5 s (top-left), 5 s (top-right) and 10 s (bottom) contact time.

<p>Higher contact times result in higher probability densities at higher rupture positions and narrower slope distributions. Sariisik et al. stated that slopes above -30 pN/<i>μ</i>m indicate tethering prior to the rupture event [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0176207#pone.0176207.ref031" target="_blank">31</a>]. Since our cantilever retraction speed was 5 <i>μ</i>m, tethers occur if slopes are above -150 pN/s, which is the case for all our measurements. The figure on the bottom also includes the corresponding histograms for slope and rupture position distributions. The axes of ordinates of these histograms represent counts.</p

Pathogenic <i>A. castellanii</i> adhere to mannose-agarose coated beads.

<p><i>Left</i>: <i>A. castellanii</i> trophozoites adhering to a mannose-agarose coated bead. White arrows indicate trophozoites at the edge of the sphere. The amount of acanthamoebae adhering to the bead and the total amount of acanthamoebae were counted directly, 2 h and 4 h after cell seeding. <i>Right</i>: Comparison of <i>A. castellanii</i> and <i>A. comandoni</i> adhesion to mannose-agarose and sepharose beads. Only a few <i>A. comandoni</i> adhered to the sepharose or mannose-agarose coated beads. A large amount of <i>A. castellanii</i> adhered already at short times and the number of adhering acanthamoeba strongly increased with time. Only a few <i>A. castellanii</i> adhered to sepharose beads. Scalebar: 100<i>μ</i>m.</p