(Color online) Interaction between 3-aminopropyltriethoxysilane functionalized cantilevers (▲) and Shewanella-functionalized cantilevers (●) on magnetite (100), magnetite (111), and hematite (001) crystal faces. Mean force-separation curves are shown. Approach curves are shown as open symbols, retraction curves as closed symbols, negative values represent attractive forces. Error bars for retraction curves at 0 nm separation represent 95% Bonferroni confidence intervals of the mean force of adhesion. All measurements were made at pH 7 in a PIPES-buffered basal medium. Cantilever spring constant (ksp) was calculated at 0.06 N m-1 as shown. Insets show the forces generated upon approach at short separation distances.