The <i>mcp5</i> mutant has no defect in motility and chemotaxis <i>in vitro</i>.

<p>(<b>A</b>) Swimming plate assay. Swimming plate assays for wild-type <i>B</i>. <i>burgdorferi</i> B31M, the <i>mcp5</i> mutant, and the <i>mcp5</i> complemented strain were performed using 0.35% agarose with BSK-II medium diluted 1:10 with DPBS. The diameters of the swim rings were measured, and average diameters of each strain were calculated from four independent plates. The <i>flaB</i> mutant (Δ<i>flaB</i>) served as a negative control. (<b>B</b>) Motion tracking analysis. Spirochetes were video captured using a computer-based motion tracking system. The average cell swimming velocities (μm/s) of tracked cells were calculated. (<b>C</b>) Capillary chemotaxis assays. <i>B</i>. <i>burgdorferi</i> cells were resuspended in the motility buffer and subjected to capillary assays for chemotaxis to acetylglucosamine and rabbit serum. Spirochetes were enumerated using Petroff-Hausser counting chambers under a dark-field microscope. For the tracking, swimming plate, and capillary assays, the results are expressed as means ± standard errors of the means (SEM). The significance of the difference between different strains was evaluated with an unpaired Student <i>t</i> test (<i>P</i> value < 0.01).</p> <p>(DOCX)</p>