The Stealthy Microbe Behind Syphilis

In 1905, scientists Fritz Schaudinn and Erich Hoffmann made a discovery that would change the history of infectious disease research: the identification of Treponema pallidum, the bacterium responsible for syphilis.

- TAPAN KUMAR MAITRA

In 1905, scientists Fritz Schaudinn and Erich Hoffmann made a discovery that would change the history of infectious disease research: the identification of Treponema pallidum, the bacterium responsible for syphilis. Over a century later, this spiral-shaped microbe continues to challenge medicine with its stealth, endurance, and resilience.

Treponema pallidum belongs to the genus Treponema and appears under the microscope as thin spiral threads with uniform coils. These organisms measure 10 to 13 micrometers in length and around 0.13 to 0.15 micrometers in width. Their DNA has a guanine-cytosine content ranging from 32 to 50 per cent. Electron microscopy reveals a three-layered outer membrane, beneath which lie basal bodies and thread-like fibrils. Each end of the cell typically bears three fibrils. Inside, the cytoplasm contains ribosomes, a nucleoid vacuole, and mesosomes. As the organisms age, they often form cyst-like structures. They reproduce by longitudinal fission and display active motility through rotating, bending, and undulating movements. Notably, they do not take up stains well, making detection difficult.

In response to environmental stress or drug exposure, these bacteria may curl into ball-like cysts, shielded by a mucin-like membrane that makes them impermeable. These cysts can lie dormant in the human body for extended periods. Under favorable conditions, they revert to granules and eventually return to their characteristic spiral form. This transformation is part of the organism's defense mechanism, allowing it to withstand inadequate or short-duration treatment.

There is no confirmed evidence of distinct serological types of