Spirochaete

Spirochaetes
Treponema pallidum spirochetes.
Scientific classification
Domain:	Bacteria
Phylum:	Spirochaetes
Class:	Spirochaetes
Order:	Spirochaetales Buchanan 1917
Families
Spirochaetaceae    Borrelia    Brevinema    Cristispira    Spirochaeta    Spironema    Treponema Brachyspiraceae    Brachyspira (Serpulina) Leptospiraceae    Leptospira    Leptonema (bacteria)

Spirochaetes (also spelled Spirochetes) belong to a phylum of distinctive Gram-negative bacteria, which have long, helically coiled (spiral-shaped) cells.^[1] Spirochetes are chemoheterotrophic in nature, with lengths between 5 and 250 µm and diameters around 0.1-0.6 µm.^{[citation needed]}

Spirochaetes are distinguished from other bacterial phyla by the location of their flagella, sometimes called axial filaments, which run lengthwise between the cell wall and outer membrane. 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 spirochetes 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:

• Leptospira species, which causes leptospirosis^[2]
• Borrelia burgdorferi, which causes Lyme disease
• Borrelia recurrentis, which causes relapsing fever^[3]
• Treponema pallidum, which causes syphilis
• Treponema pertenue, which causes yaws

Cavalier-Smith has postulated that the Spirochaetes belong in a larger clade called Gracilicutes.^[4]

Historical

Salvarsan, the first antibiotic in medical history, was effective against spirochaetes only and was primarily used to cure syphilis.

It has been suggested by biologist Lynn Margulis that eukaryotic flagella were derived from symbiotic spirochaetes,^[5] but few biologists accept this, as there is no close structural similarity between the two.

See also

• Flagellum
• Treponema pallidum
• Lyme disease microbiology
• Borrelia
• Bacteriology
• Prokaryote

References