Spirochaetes are chemoheterotrophic in nature, with lengths between 3 and 500 um and diameters around 0.09 to at least 3 um.

Spirochaetes are distinguished from other bacterial phyla by the location of their flagella, called endoflagella, or periplasmic flagella, which are sometimes called axial filaments. Endoflagella are anchored at each end (pole) of the bacterium within the periplasmic space (between