FIG 1 .

Long-term cultivation of T. pallidum subsp. pallidum Nichols in a tissue culture system (experiment 1). Primary cultures represent the results obtained without subculture. The 500-µl passages used transfer of that volume for each subculture, whereas the low-inoculum passages used lower volumes (100 µl to 250 µl). (A) In this “sawtooth” plot, the number of T. pallidum organisms per culture upon harvest and the number inoculated in the next subculture are shown for each time point. (B) Percent motility provides a measure of viability. (C) Average (Ave.) generation time, representing the time in hours divided by log₂(fold increase) for each time point. T. pallidum per-culture and percent motility values represent means ± SE of results from three biological replicates.