Spirochaete
Spirochaetes English pronunciation: /ˈspʌɪrə(ʊ)kiːt/ (also spelled spirochetes) belong to a phylum of distinctive diderm (double-membrane) bacteria, most of which have long, helically coiled (corkscrew-shaped or spiraled, hence the name) cells. Spirochaetes are chemoheterotrophic in nature, with lengths between 5 and 250 µm and diameters around 0.1–0.6 µm.
Spirochaetes are distinguished from other bacterial phyla by the location of their flagella, sometimes called axial filaments, which run lengthwise between the bacterial inner membrane and outer membrane in periplasmic space. These cause a twisting motion which allows the spirochaete to move about. When reproducing, a spirochaete will undergo asexual transverse binary fission.
Most spirochaetes are free-living and anaerobic, but there are numerous exceptions.
Classification
The spirochaetes are divided into three families (Brachyspiraceae, Leptospiraceae, and Spirochaetaceae), all placed within a single order (Spirochaetales). Disease-causing members of this phylum include the following:
