FIGURE 2.

Deletion of flhF_Bb affects the cell growth, shape and motility of B. burgdorferi. (a) The growth curves of WT, ΔflhF and ΔflhF^com strains. Cells were grown in BSK-II medium (pH 7.6) at 34°C for 8 days. Cell counting was repeated in triplicates in two independent experiments, and the results were expressed as means ± SD. (b) Dark-field microscopic analysis of WT and ΔflhF mutant. The cells were grown in BSK-II medium to the early stationary phase and then subjected to microscopic analysis under dark-field illumination at x 400 magnifications using a Zeiss Axiostar Plus microscope. (c) Swimming plate assays of WT, ΔflhF and ΔflhF^com strains. For this assay, B. burgdorferi cells (5 μl) were stab-inoculated into semisoft agar plates containing dPBS-diluted (10:1) BSK-II medium and 0.35% agarose, as previously described (Motaleb et al., 2000). ΔflaB, a nonmotile mutant, was used as a control to determine the initial inoculation size on the plates