Borrelia

Article By:

Burgdorfer, Willy Rocky Mountain Laboratories, Department of Health and Human Services, National Institutes of Health, Hamilton, Montana.

Rosa, Patricia National Institutes of Health, Hamilton, Montana.

Last reviewed:October 2019

DOI:https://doi.org/10.1036/1097-8542.091950

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• Borrelia, published March 2015:Download PDF Get Adobe Acrobat Reader

A genus of spirochetes (bacteria assigned to the family Spirochaetaceae) that have a unique genome composed of a linear chromosome and numerous linear and circular plasmids. Members of the genus Borrelia (borreliae) [see illustration] are motile, helical organisms with 4–30 uneven, irregular coils, and they measure 5–25 μm in length and 0.2–0.5 μm in width. Their locomotory apparatus consists of 15–22 fibrils coiled around the cell body and situated between the elastic envelope and cytoplasmic membrane. Motion is forward and backward, laterally by bending and looping, and corkscrewlike. Borreliae multiply by binary fission (a method of asexual reproduction accomplished by the splitting of a parent cell into two equal, or nearly equal, parts, with each growing to parental size and form). Epidemiologically, borreliae are notable for causing Lyme disease and relapsing fever. See also: Bacteria; Bacteriology; Chromosome; Lyme disease; Medical bacteriology; Microbiology; Plasmid; Relapsing fever

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