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Biology LibreTexts

8. 11.6: Spirochaetes

Spirochaetes are characterized by the presence of a double-membrane and long, spiral-shaped cells that are chemoheterotrophic.




Outline the characteristics associated with spirochaetes and the associated diseases



Key Points


  • Spirochaetes are chemoheterotrophic in nature and capable of thriving in anaerobic conditions.
  • The spirochaetes are categorized by the presence of axial filaments which run lengthwise between the inner and outer membranes in periplasmic space.
  • Spirochaetes are capable of causing diseases including leptospirosis, Lyme disease, relapsing fever and syphilis.


Key Terms


  • periplasmic: surrounding the plasma of a bacterium

The spirochaetes belong to a phylum of distinctive double-membrane bacteria that are characterized by their long, spiral-shaped cells. The spirochaetes are chemoheterotrophic in nature, free-living and capable of thriving in anaerobic environments. They are often distinguished from other bacterial phyla by the location of their flagella. The flagella, in spirochaetes, runs lengthwise between the inner and outer membranes in the periplasmic space. Often referred to as axial filaments, there is a twisting motion that occurs which allows the spirochaete to move. During reproduction, the spirochaete is capable of undergoing asexual reproduction via binary fission. The binary fission allows for production of two separate spirochaetes.

The spirochaetes can be divided into three families which include: BrachyspiraceaeLeptospiraceae, and Spirochaetaceae. These families are all categorized under a single order, Spirochaetales. There are specific species of spirochaetes that are considered to be pathogenic. Some of the pathogenic species include:

  • Leptospira, the cause of leptospirosis – leptospirosis is transmitted to humans from animals and a common form of transmission is by allowing contaminated water to come in contact with unhealed breaks in the skin, eyes and mucous membranes. The water becomes contaminated by coming into contact with the urine of an infected animal.
  • Borrelia burgdorferi, Borrelia garinii, Borrelia afzelii, the cause of lyme-disease
  • Borrelia recurrentis, the cause of relapsing fever
  • Treponema pallidum, subspecies pallidum, the cause of syphilis
  • Treponema pallidum, subspecies pertenue, the cause of yaws (tropical infection of the skin, bones and joints)
  • Brachyspira pilosicoli and Brachyspira aalborgi, the cause of intestinal spirochetosis