SPIROCHAETAE

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KINGDOM SPIROCHAETAE

INTRODUCTION TO THE SPIROCHAETAE AND ITS SINGLE PHYLUM, SPIROCHAETOBACTERIA

Spirochaetae (spi-ro-KE-te) is derived from a Latin root meaning spiraled or coiled (spira) and a Greek root meaning long hair or mane (khaite -χαίτη). The name is descriptive of the group and refers to the long hair-like spiraled cells of this group.

The spirochaetes tend to be elongate and spiral with a many polar flagella that stay within the outer membrane and wind down the cell from both ends and produce the characteristic corkscrew appearance (Figures A&B). Taxa within this group may be free-living. Some like Treponema, the causative agent of syphilis, are parasites.

A. Free-living Spirochaeta from Mono Lake.

B. A TEM cross section of a Treponema cell. OE=outer envelope, AF=axial filament, WM=membrane; BF=body fibrils (internal flagella)

Images taken from:
A: http://science.nasa.gov/headlines/y2003/images/monolake/Sa_med.jpg
B: http://biology.kenyon.edu/Microbial_Biorealm/bacteria/treponema/treponema.htm

SYNOPTIC DESCRIPTION OF THE SPIROCHAETOBACTERIA

The following description comes mainly from Margulis and Schwartz (1998), Barnes (1984), Brock et al. (1994), and Tudge (2000).

I. SYNONYMS: Spirochaetes

II. PHYLUM CHARACTERISTICS:

A. Structure

Cell Form: Helically spiral.

Cell Wall: Flexible outer wall; gram-.

Motility: Motile but flagella wind around the cell in the space between the inner and outer membranes; flagella 2->200 flagella inserted at the poles of the cell and overlap in the central region.

B. Physiology

O₂ Tolerance: Most are obligate anaerobes.

Substrates: Chemoheterotrophs; typically, they ferment sugars and amino acids.

Products: The fermentation products are CO₂, small organic acids and alcohols.

C. Other: Cells single and move in complex loops and coils.

D. Ecology: Free-living, particularly in organic-rich and oxygen-poor environments. Also, they grow as commensals and as parasites of plants and animals.

SYSTEMATICS OF THE SPIROCHAETOBACTERIA

This system is a modification of Margulis and Schwartz (1988 and 1998) in which the phylum is designated B-4. I have raised the phylum of Margulis and Schwartz (1998) to the level of Kingdom with a single phylum. This group segregates well along the lines of cell structure. Bergey's Manual of Systematic Bacteriology, volume 1, section 1 (Holt 1984) considers the group to be contained within a single Order (Spirochaetes) within the Division (phylum) Gracilicutes. Krieg (1984) acknowledges 2 major groups (families) within the order. Bergey's Manual of Systematic Bacteriology, 2nd edition (Garrity et al. 2001 and 2003) treats the taxa that I include in the Spirochaetobacteria a natural group (phylum with a single class, a single order and three families).

The Spirochaetobacteria is very likely a natural group. The characteristic location of the polar flagella within the outer membrane is almost certainly a synapomorphy.

HIERARCHICAL CLASSIFICATION OF THE SPIROCHAETOBACTERIA

This system follows that of Margulis and Schwartz (1998) and Garrity et al. (2001 and 2003) who treat the spirochaetes as a phylum.

CLASS SPIROCHAETIAE

ORDER SPIROCHAETIALES

Spirochaeta, Borrelia, Brevinema, Clevelandina, Cristispira, Diplocalyx, Hollandia, Pillotina, Treponema.

Serpulina, Brachyspira.

Leptonema, Leptospira.

This page is maintained by Jack R. Holt. Last revised: 04/22/2008.