Chemotaxis of oral treponemes toward sera and albumin of rabbit

The motility and chemotaxis of human oral spirochetes Treponema denticola ATCC 35404, T. medium ATCC 700293, and T. vincentii ATCC 35580 were examined by a capillary assay method. Of five sera three human oral treponemes were dominantly chemoattractant to the rabbit serum. The checkerboard analysis of chemotaxis toward rabbit serum clearly showed that the motile T. denticola cells swam toward the culture media containing higher concentrations of the rabbit serum. T. denticola chemotaxis to the rabbit serum was clearly reduced by heating serum, and rabbit albumin contributed by 60 to 70% to its chemotaxis to the rabbit serum. Western blotting analysis demonstrated that these treponemes possessed rabbit albumin-binding polypeptides with approximate molecular sizes of 65 kDa and 70 kDa. Immunoelectron microscopy demonstrated that a 65 kDa rabbit albumin-binding polypeptide was located on the outer envelopes, suggesting that the rabbit albumin-binding polypeptide is responsible for chemotaxis toward rabbit serum.