Figure 2.

Bond dissociation rates and interaction velocities of Tp0751-expressing B. burgdorferi. B. burgdorferi interactions with HUVEC in flow chambers at 0.5 and 1 dyn/cm² were captured by particle tracking of interaction trajectories (tracks) in time lapse sequences. (a) Sample time lapse projections depicting interaction tracks of individual bacteria (1 color/bacterium) captured at 1 dyn/cm² over 2 min. Scale bars: 38 µm. (b) The linear regression of the log-transformed number of interactions versus the lifetime (seconds) of the spirochete for 4 representative tracks (1 track for each of the 4 strains). The negative slope of each regression was an estimate of the dissociation rate (K_off) of the spirochete, as described in the Materials and Methods. (c) Mean ± SEM dissociation rates (K_off/off-rates) for individual load-bearing adhesion complexes mediating bacterial-endothelial interactions under flow. (d) Velocities of interacting bacteria (mean ± 95% CI). In (b–d), bond dissociation rates and interaction velocities were calculated from interactions obtained at both 0.5 and 1 dyn/cm². N = 4 and N = 8 independent flow chamber experiments for each strain at 0.5 and 1 dyn/cm², respectively. Eight replicate experiments were conducted at 1 dyn/cm² to obtain sufficient interaction numbers for tracking. Strains: Negative control strain: BBK32-deficient non-infectious adhesion-attenuated B31-A-derived strain (Parent; GCB706: Supplementary Table S1). Positive control strains: Parent expressing B. burgdorferi vascular adhesin BBK32 (Bb-BBK32); BBK32-expressing B31-derived infectious strain (Infectious; GCB726: Supplementary Table S1). Bb-Tp0751: Parent expressing Tp0751. Numbers of interactions analyzed/strain: Parent (408), Infectious (647), Bb-BBK32 (578), and Bb-Tp0751 (288). R² values for linear regressions in (b): >0.9. Statistics: one-way ANOVA with Holm-Sidak post-tests (c), one-way Kruskal-Wallis ANOVA with Dunn’s post-tests (d). *Indicates p < 0.05 vs parent. ⁺Indicates p < 0.05 vs Bb-BBK32.