Staining of Bb-HP, Ba or Bg with CFSE. Panels (A)-(C) show histograms representative of three to eight different experiments. CFSE stained borreliae are shown as grey histograms. Borreliae treated according to the staining protocol with the exception of using PBS instead of CFSE served as negative control and are shown as white histograms. Percentages of fluorescent borreliae as mean ± standard deviation (SD) of three to eight different experiments are shown above the histograms. Panels (D)-(F) show microscopic images of CFSE-stained Bb-HP, Ba and Bg, respectively, and are representative of two to three experiments.