Figure 7.

Serum susceptibility testing of spirochetes. (A) A growth inhibition assay was used to investigate susceptibility to human serum of B. burgdorferi (Bb) strain LW2, B. garinii (Bg) G1, and transformant G1/pBS_CbiA. Spirochetes were incubated in either 50% NHS (filled squares) or 50% HIS (filled triangles) over a cultivation period of 9 days at 33 °C, respectively. Color changes were monitored by measurement of the absorbance at 562/630 nm which is inversely proportional to the acidification of the culture medium. All experiments were performed at least three times, with each test conducted in triplicate with very similar results. For clarity, only data from one representative experiment is shown. Error bars represent ±SD. (B) Western blot analysis of spirochetes collected at different time points. Cell lysates (250 ng each) subjected to 4–20% SDS gels were analyzed by Western blotting to detect FlaB and CbiA using a monoclonal anti-FlaB antibody L41 1C11 (1:1000) and an anti-rabbit Ab (1:500), respectively. The full-length versions are presented in Supplementary Figure S8. (C) Serum susceptibility testing of spirochetes collected at different time points. Spirochetes were incubated in 50% NHS at 37 °C for 1 h. Dark-field microscopy were investigated for calculating the percentage of motile spirochetes. ns, not statistically significant. ***P < 0.001, **P < 0.01.