The Spirochaetes are distinguished from all other
bacteria by their slender helical mor-phology and corkscrew-like movement. This
is made possible by endoflagella (axial
filaments), so-called because they are enclosed in the space between the cell
and a flexi-ble sheath that surrounds it.
Spirochaetes comprise both aerobic and anaerobic
bacteria that inhabit a wide range of habitats, including water and soil as
well as the gut and oral cavities of both vertebrate and invertebrate animals.
Some species are important pathogens of humans, including Treponema pallidum
(syphilis) and Leptospira interrogans (leptospirosis).
Representative genera: Treponema, Leptospira