FN1 and syphilis: This work aimed to expand our previous knowledge on T. pallidum TP0136-Fn interaction dynamics by investigating 1) whether additional TP0136 variants are found among other syphilis strains, 2) whether the tp0136 transcriptional pattern would vary over time during experimental syphilis infection, 3) how efficiently TP0136 would adhere to cellular Fn compared to plasma Fn, and 4) which region(s) of TP0136 is responsible for binding to Fn.