Spirochaete. Coloured transmission electron micrograph (TEM) of two spirochaete (Treponema sp. ) bacteria. These bacteria are from the mouth of a person with periodontal disease. These elongated spiral-shaped bacteria (spirochaetes) lack rigid cell walls. 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."