Explore the recorded discovery and history of Treponema pallidum, with source links and stated limits.
PHAC describes T. pallidum as a spiral-shaped, microaerobic, non-spore-forming, motile bacterium measuring 6 to 20 micrometres in length and 0.1 to 0.2 micrometres in diameter, with a protoplasmic cylinder and cytoplasmic membrane bound by a thin peptidoglycan sacculus and outer membrane; although structurally double-membraned, its outer membrane lacks lipopolysaccharides and differs markedly from a typical Gram-negative outer membrane. It could not be grown in pure culture for more than a century, and a long-term tissue-culture system was only reported in 2018. WHO estimated 7.1 million new syphilis infections worldwide in 2020, and 1.1 million pregnant women estimated infected in 2022, resulting in over 390,000 adverse birth outcomes. This profile describes the subspecies pallidum, which causes venereal syphilis.
LPSN records the basonym “Spirochaeta pallida” Schaudinn and Hoffmann 1905, with the combination Treponema pallidum published by Schaudinn in the same year in Deutsche Medizinische Wochenschrift and retained on the 1980 Approved Lists of Bacterial Names. The epithet pallidum means pale, describing how faintly the organism stains.
Edmondson, Hu and Norris reported continuous in vitro multiplication of T. pallidum subsp. pallidum for over six months using modified medium TpCM-2 with a microaerobic rabbit epithelial cell coincubation system, applied to the Nichols strain and to the recent isolates UW231B and UW249B. PHAC records the same 2018 milestone. This is a laboratory advance, not a change in the disease.
These references do not identify a first person ever infected. Syphilis was described as a disease centuries before the organism was seen in 1905, so the identification date cannot stand in for a first case, and the long-running historical debate about the disease’s geographic origin is not settled by these sources.
Source check: 2026-09-20. Educational content; independent scientific review remains pending.