Fig. 2. Spermidine is the preferred polyamine transported by B. burgdorferi.

Curve of uptake of radioactive spermidine and putrescine by B. burgdorferi B31-A3 strain was measured over a 10-min time course. Cells were grown to mid-log phase, washed and resuspended to a cell density of 6 x 10⁸ cells/ml in HN buffer supplemented with 6 mM glucose. Tritium labelled polyamine (5μCi) was added to the cell suspensions and incubated at 34°C for the duration of the experiment. Polyamine amounts (pmol) in samples were determined against a calibration performed with authentic labeled substrate. The protein concentration was determined using a BCA Protein Assay with bovine serum albumin as a standard. Dotted lines represent the linear regression. Data represent means ± standard deviation of three independent experiments.