Treponema Pallidum

Treponema Pallidum is a spirochete bacteria that has two subspecies that cause human disease. These are T. pallidum subspecies pallidum, which causes venereal syphilis; and T. pallidum subspecies pertenue, which causes yaws. Both of these subspecies are members of the family, Spirochaetales, which also incudes the spirochetes Leptospira, the casue of the hiuman disease, leptospirosis, and Borrelia, a genus of several species of spirochetes that cause the human diseases of relapsing fever and Lyme disease.

References

Sheila A. Lukehart. Chapter 153. "Syphilis" in Dennis L. Kasper, Eugene Braunwald, Anthony S. Fauci, Stephen L. Hauser, Dan L. Longo, J. Larry Jameson, and Kurt J. Isselbacher, Eds.Harrison's Principles of Internal Medicine, 16th Edition