Spirochaetes (or Spirochetes) are the phylum Spirochaetae. These are double-membrane bacteria with long, helically coiled (spiral-shaped) cells.

Spirochaetes are bacteria. They have flagella, which run lengthwise between the cell wall and outer membrane. The flagella cause a twisting motion which moves the spirochaete about.

Most spirochaetes are free-living and anaerobic, but there are many parasitic species.

The spirochaetes are divided into three families (Brachyspiraceae, Leptospiraceae, and Spirochaetaceae). They are all put in a single order, the Spirochaetales. Disease-causing members of this phylum include:

• Leptospira species, some of which which cause leptospirosis^[1]
• Borrelia species, some of which cause Lyme disease
  • Borrelia recurrentis, which causes relapsing fever.^[2]
• Treponema pallidum subspecies which cause syphilis and yaws.
• Brachyspira species, which cause intestinal spirochaetosis.^[3]

• Introduction to the Spirochetes. UCMP. [1]