<unk> s is a phylum of distinctive Gram-negative bacteria, which have long, helically coiled cells.<unk> s are chemoheterotrophic in nature, with lengths between 5 and 250 µm and diameters around 0.1-0.6 µm.[citation needed]
Spriochetes are distinguished from other bacterial phyla by the presence of flagella, sometimes called axial filaments, running lengthwise between the cell membrane and outer membrane. These cause a twisting motion which allows the<unk>  to move about.
The<unk> s are divided into three families (Brachyspiraceae, Leptospiraceae, and<unk> ceae), all placed within a single order <unk> les).
Leptospira species, which causes leptospirosis
Borrelia burgdorferi, which causes Lyme disease
Borrelia recurrentis, which causes relapsing fever
Treponema pallidum, which causes syphilis
Most<unk> s are free-living and anaerobic, but there are numerous exceptions, including the above.
Cavalier-Smith has postulated that the<unk> s belong in a larger clade called Gracilicutes.
Spirochaete
Sporophyte
Arthropod
Hookworm
Parasitic worm
Cestoda
Schistosoma
Pinworm