Figure 4.

Analysis of velocity of the fcpB⁻ mutant cells in liquid viscous media. Dark-field video microscopy and tracking analysis were used to measure the average velocities of individual cells in viscous liquid media containing 1% methyl-cellulose. (A) Scatter plot of the velocities of individual cells shows that the difference in median velocity (horizontal bar) between the wild-type and mutant populations is not statistically significant. (B) Histogram showing the relative frequency of the velocities of individual cells. Note that depletion of FcpB affects the proportion of highly motile leptospires in a population. (C) The range of leptospiral cell velocities in a population is reduced in the fcpB⁻ mutant, with a lower maximum velocity, when compared to the wild-type strain. (D) Representative trajectories of wild-type and fcpB⁻ mutant over 5 s, illustrating that the fcpB⁻ mutant population is deficient in highly-motile leptospires.