Spirochaete. Coloured transmission electron micrograph (TEM) of a spirochaete (Treponema sp. ) bacterium. This bacterium is from the mouth of a person with periodontal disease. This elongated spiral-shaped bacterium (spirochaete) lacks a rigid cell wall. Pathogenic species of Treponema include T. pallidum which causes syphilis; T. carateum which causes the skin disease pinta" in tropical America; and T. pertenue which causes yaws in Africa. In syphilis, the bacteria may be found in most parts of the body. Negatively stained. Magnification unknown."